/*
  Racket
  Copyright (c) 2004-2011 PLT Scheme Inc.
  Copyright (c) 1995-2001 Matthew Flatt

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301 USA.

  libscheme
  Copyright (c) 1994 Brent Benson
  All rights reserved.
*/

/* This file contains the Racket reader, including the normal reader
   and the one for .zo files. The normal reader is a recursive-descent
   parser. The really messy part is number parsing, which is in a
   different file, numstr.c. */

/* Rule on using scheme_ungetc(): the reader is generally allowed to
   use scheme_ungetc() only when it will definitely re-read the
   character as it continues. If the character will not be re-read
   (e.g., because an exception will be raised), then the reader must
   peek, instead. However, read-symbol uses ungetc() if the port does
   not have a specific peek handler, and in that case, read-symbol
   only ungetc()s a single character (that had been read by itself). */

#include "schpriv.h"
#include "schmach.h"
#include "schminc.h"
#include "schcpt.h"
#include "schvers.h"
#include <stdlib.h>
#include <ctype.h>
#ifdef USE_STACKAVAIL
# include <malloc.h>
#endif

#define MAX_QUICK_SYMBOL_SIZE 64

/* Init options for embedding: */
/* these are used to set initial config parameterizations */
SHARED_OK int scheme_square_brackets_are_parens = 1;
SHARED_OK int scheme_curly_braces_are_parens = 1;
/* global flag set from environment variable */
SHARED_OK static int use_perma_cache = 1;

THREAD_LOCAL_DECL(int scheme_num_read_syntax_objects);


/* read-only global symbols */
SHARED_OK static char *builtin_fast;
SHARED_OK static unsigned char delim[128];
SHARED_OK static unsigned char cpt_branch[256];

/* Table of built-in variable refs for .zo loading: */
SHARED_OK static Scheme_Object **variable_references;

ROSYM static Scheme_Object *quote_symbol;
ROSYM static Scheme_Object *quasiquote_symbol;
ROSYM static Scheme_Object *unquote_symbol;
ROSYM static Scheme_Object *unquote_splicing_symbol;
ROSYM static Scheme_Object *syntax_symbol;
ROSYM static Scheme_Object *unsyntax_symbol;
ROSYM static Scheme_Object *unsyntax_splicing_symbol;
ROSYM static Scheme_Object *quasisyntax_symbol;
ROSYM static Scheme_Object *paren_shape_symbol;
ROSYM static Scheme_Object *terminating_macro_symbol;
ROSYM static Scheme_Object *non_terminating_macro_symbol;
ROSYM static Scheme_Object *dispatch_macro_symbol;
ROSYM static Scheme_Object *honu_comma;
ROSYM static Scheme_Object *honu_semicolon;
ROSYM static Scheme_Object *honu_parens;
ROSYM static Scheme_Object *honu_braces;
ROSYM static Scheme_Object *honu_brackets;
ROSYM static Scheme_Object *honu_angles;
/* For matching angle brackets in Honu mode: */
ROSYM static Scheme_Object *honu_angle_open;
ROSYM static Scheme_Object *honu_angle_close;
/* For recoginizing unresolved hash tables and commented-out graph introductions: */
ROSYM static Scheme_Object *unresolved_uninterned_symbol;
ROSYM static Scheme_Object *tainted_uninterned_symbol;

/* local function prototypes */
static Scheme_Object *read_case_sensitive(int, Scheme_Object *[]);
static Scheme_Object *read_bracket_as_paren(int, Scheme_Object *[]);
static Scheme_Object *read_brace_as_paren(int, Scheme_Object *[]);
static Scheme_Object *read_accept_graph(int, Scheme_Object *[]);
static Scheme_Object *read_accept_compiled(int, Scheme_Object *[]);
static Scheme_Object *read_accept_box(int, Scheme_Object *[]);
static Scheme_Object *read_accept_pipe_quote(int, Scheme_Object *[]);
static Scheme_Object *read_decimal_as_inexact(int, Scheme_Object *[]);
static Scheme_Object *read_accept_dot(int, Scheme_Object *[]);
static Scheme_Object *read_accept_infix_dot(int, Scheme_Object *[]);
static Scheme_Object *read_accept_quasi(int, Scheme_Object *[]);
static Scheme_Object *read_accept_reader(int, Scheme_Object *[]);
static Scheme_Object *read_accept_lang(int, Scheme_Object *[]);
#ifdef LOAD_ON_DEMAND
static Scheme_Object *read_delay_load(int, Scheme_Object *[]);
#endif
static Scheme_Object *print_graph(int, Scheme_Object *[]);
static Scheme_Object *print_struct(int, Scheme_Object *[]);
static Scheme_Object *print_box(int, Scheme_Object *[]);
static Scheme_Object *print_vec_shorthand(int, Scheme_Object *[]);
static Scheme_Object *print_hash_table(int, Scheme_Object *[]);
static Scheme_Object *print_unreadable(int, Scheme_Object *[]);
static Scheme_Object *print_pair_curly(int, Scheme_Object *[]);
static Scheme_Object *print_mpair_curly(int, Scheme_Object *[]);
static Scheme_Object *print_honu(int, Scheme_Object *[]);
static Scheme_Object *print_syntax_width(int, Scheme_Object *[]);
static Scheme_Object *print_reader(int, Scheme_Object *[]);
static Scheme_Object *print_as_qq(int, Scheme_Object *[]);
static Scheme_Object *print_long_bool(int, Scheme_Object *[]);

static int scheme_ellipses(mzchar* buffer, int length);

#define NOT_EOF_OR_SPECIAL(x) ((x) >= 0)

#define mzSPAN(port, pos)  ()

#define NOT_ENABLED_str " not enabled in the current context"

#define isdigit_ascii(n) ((n >= '0') && (n <= '9'))

#define scheme_isxdigit(n) (isdigit_ascii(n) || ((n >= 'a') && (n <= 'f')) || ((n >= 'A') && (n <= 'F')))

#define RETURN_FOR_SPECIAL_COMMENT  0x1
#define RETURN_FOR_HASH_COMMENT     0x2
#define RETURN_FOR_DELIM            0x4
#define RETURN_FOR_COMMENT          0x8
#define RETURN_HONU_ANGLE           0x10

static MZ_INLINE intptr_t SPAN(Scheme_Object *port, intptr_t pos) {
  intptr_t cpos;
  scheme_tell_all(port, NULL, NULL, &cpos);
  return cpos - pos + 1;
}

/* For cases where we'd rather report the location as just the relevant prefix: */
#define MINSPAN(port, pos, span) (span)

#define mz_shape_cons 0
#define mz_shape_vec 1
#define mz_shape_hash_list 2
#define mz_shape_hash_elem 3
#define mz_shape_vec_plus_infix 4

typedef struct Readtable {
  Scheme_Object so;
  Scheme_Hash_Table *mapping; /* pos int -> (cons int proc-or-char); neg int -> proc */
  char *fast_mapping;
  Scheme_Object *symbol_parser; /* NULL or a Scheme function */
  char **names; /* error-message names */
} Readtable;

typedef struct ReadParams {
  MZTAG_IF_REQUIRED
  char can_read_compiled;
  char can_read_pipe_quote;
  char can_read_box;
  char can_read_graph;
  char can_read_reader;
  char can_read_lang;
  char case_sensitive;
  char square_brackets_are_parens;
  char curly_braces_are_parens;
  char read_decimal_inexact;
  char can_read_dot;
  char can_read_infix_dot;
  char can_read_quasi;
  char honu_mode;
  char skip_zo_vers_check;
  Readtable *table;
  Scheme_Object *magic_sym, *magic_val;
  Scheme_Object *delay_load_info;
  Scheme_Object *read_relative_path;
} ReadParams;

#define THREAD_FOR_LOCALS scheme_current_thread
#define local_list_stack (THREAD_FOR_LOCALS->list_stack)
#define local_list_stack_pos (THREAD_FOR_LOCALS->list_stack_pos)

static Scheme_Object *read_list(Scheme_Object *port, Scheme_Object *stxsrc,
				intptr_t line, intptr_t col, intptr_t pos,
				int opener, int closer,
				int shape, int use_stack,
				Scheme_Hash_Table **ht,
				Scheme_Object *indentation,
				ReadParams *params);
static Scheme_Object *read_string(int is_byte, int is_honu_char,
				  Scheme_Object *port, Scheme_Object *stxsrc,
				  intptr_t line, intptr_t col, intptr_t pos,
				  Scheme_Hash_Table **ht,
				  Scheme_Object *indentation,
				  ReadParams *params, int err_ok);
static Scheme_Object *read_here_string(Scheme_Object *port, Scheme_Object *stxsrc,
				       intptr_t line, intptr_t col, intptr_t pos,
				       Scheme_Object *indentation,
				       ReadParams *params);
static Scheme_Object *read_quote(char *who, Scheme_Object *quote_symbol, int len,
				 Scheme_Object *port, Scheme_Object *stxsrc,
				  intptr_t line, intptr_t col, intptr_t pos,
				 Scheme_Hash_Table **ht,
				 Scheme_Object *indentation,
				 ReadParams *params);
static Scheme_Object *read_vector(Scheme_Object *port, Scheme_Object *stxsrc,
				  intptr_t line, intptr_t col, intptr_t pos,
				  int opener, char closer,
				  intptr_t reqLen, const mzchar *reqBuffer,
				  Scheme_Hash_Table **ht,
				  Scheme_Object *indentation,
				  ReadParams *params, int allow_infix);
static Scheme_Object *read_number(int init_ch,
				  Scheme_Object *port, Scheme_Object *stxsrc,
				  intptr_t line, intptr_t col, intptr_t pos,
				  int, int, int, int,
				  Scheme_Hash_Table **ht,
				  Scheme_Object *indentation,
				  ReadParams *params,
				  Readtable *table);
static Scheme_Object *read_symbol(int init_ch, int skip_rt,
				  Scheme_Object *port, Scheme_Object *stxsrc,
				  intptr_t line, intptr_t col, intptr_t pos,
				  Scheme_Hash_Table **ht,
				  Scheme_Object *indentation,
				  ReadParams *params,
				  Readtable *table);
static Scheme_Object *read_keyword(int init_ch,
				   Scheme_Object *port, Scheme_Object *stxsrc,
				   intptr_t line, intptr_t col, intptr_t pos,
				   Scheme_Hash_Table **ht,
				   Scheme_Object *indentation,
				   ReadParams *params,
				   Readtable *table);
static Scheme_Object  *read_delimited_constant(int ch, const mzchar *str,
                                               Scheme_Object *v,
                                               Scheme_Object *port,
                                               Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
                                               Scheme_Object *indentation,
                                               ReadParams *params, Readtable *table);
static Scheme_Object *read_character(Scheme_Object *port, Scheme_Object *stcsrc,
				     intptr_t line, intptr_t col, intptr_t pos,
				     Scheme_Hash_Table **ht,
				     Scheme_Object *indentation,
				     ReadParams *params);
static Scheme_Object *read_box(Scheme_Object *port, Scheme_Object *stxsrc,
			       intptr_t line, intptr_t col, intptr_t pos,
			       Scheme_Hash_Table **ht,
			       Scheme_Object *indentation,
			       ReadParams *params);
static Scheme_Object *read_hash(Scheme_Object *port, Scheme_Object *stxsrc,
				intptr_t line, intptr_t col, intptr_t pos,
				int opener, char closer, int kind,
				Scheme_Hash_Table **ht,
				Scheme_Object *indentation,
				ReadParams *params);
static Scheme_Object *read_reader(Scheme_Object *port, Scheme_Object *stxsrc,
				  intptr_t line, intptr_t col, intptr_t pos,
				  Scheme_Hash_Table **ht,
				  Scheme_Object *indentation,
				  ReadParams *params);
static Scheme_Object *read_lang(Scheme_Object *port, Scheme_Object *stxsrc,
                                intptr_t line, intptr_t col, intptr_t pos,
                                int get_info,
                                Scheme_Hash_Table **ht,
                                Scheme_Object *indentation,
                                ReadParams *params,
                                int init_ch);
static Scheme_Object *read_compiled(Scheme_Object *port, Scheme_Object *stxsrc,
				    intptr_t line, intptr_t col, intptr_t pos,
				    Scheme_Hash_Table **ht,
				    ReadParams *params);
static void unexpected_closer(int ch,
			      Scheme_Object *port, Scheme_Object *stxsrc,
			      intptr_t line, intptr_t col, intptr_t pos,
			      Scheme_Object *indentation,
                              ReadParams *params);
static Scheme_Object *expected_lang(const char *prefix, int ch,
                                    Scheme_Object *port, Scheme_Object *stxsrc,
                                    intptr_t line, intptr_t col, intptr_t pos,
                                    int get_info);
static void pop_indentation(Scheme_Object *indentation);
static int next_is_delim(Scheme_Object *port,
			 ReadParams *params,
			 int brackets,
			 int braces);

static int skip_whitespace_comments(Scheme_Object *port, Scheme_Object *stxsrc,
				    Scheme_Hash_Table **ht,
				    Scheme_Object *indentation,
				    ReadParams *params);

static Scheme_Object *readtable_call(int w_char, int ch, Scheme_Object *proc, ReadParams *params,
				     Scheme_Object *port, Scheme_Object *src, intptr_t line, intptr_t col, intptr_t pos,
                                     int get_info,
				     Scheme_Hash_Table **ht, Scheme_Object *modpath_stx);

#define READTABLE_WHITESPACE 0x1
#define READTABLE_CONTINUING 0x2
#define READTABLE_TERMINATING 0x4
#define READTABLE_SINGLE_ESCAPE 0x8
#define READTABLE_MULTIPLE_ESCAPE 0x10
#define READTABLE_MAPPED 0x20
static int readtable_kind(Readtable *t, int ch, ReadParams *params);
static Scheme_Object *readtable_handle(Readtable *t, int *_ch, int *_use_default, ReadParams *params,
				       Scheme_Object *port, Scheme_Object *src, intptr_t line, intptr_t col, intptr_t pos,
				       Scheme_Hash_Table **ht);
static Scheme_Object *readtable_handle_hash(Readtable *t, int ch, int *_use_default, ReadParams *params,
					    Scheme_Object *port, Scheme_Object *src, intptr_t line, intptr_t col, intptr_t pos,
					    Scheme_Hash_Table **ht);
static int readtable_effective_char(Readtable *t, int ch);
static Scheme_Object *make_readtable(int argc, Scheme_Object **argv);
static Scheme_Object *readtable_p(int argc, Scheme_Object **argv);
static Scheme_Object *readtable_mapping(int argc, Scheme_Object **argv);
static Scheme_Object *current_readtable(int argc, Scheme_Object **argv);
static Scheme_Object *current_reader_guard(int argc, Scheme_Object **argv);

/* A list stack is used to speed up the creation of intermediate lists
   during .zo reading. */

#define NUM_CELLS_PER_STACK 500

#ifdef MZ_PRECISE_GC
static void register_traversers(void);
#endif

typedef struct {
  Scheme_Type type;
  char closer;      /* expected close parent, bracket, etc. */
  char suspicious_closer; /* expected closer when suspicious line found */
  char multiline;   /* set to 1 if the match attempt spans a line */
  char quote_for_char; /* 1 => suspicious_quote refers to Honu char */
  intptr_t start_line;  /* opener's line */
  intptr_t last_line;   /* current line, already checked the identation */
  intptr_t suspicious_line; /* non-0 => first suspicious line since opener */
  intptr_t max_indent;  /* max indentation encountered so far since opener,
		       not counting indentation brackets by a more neseted
		       opener */
  intptr_t suspicious_quote; /* non-0 => first suspicious quote whose closer
			    is on a different line */
} Scheme_Indent;

#define SCHEME_OK          0x1
#define HONU_OK            0x2
#define HONU_SYM_OK        0x4
#define HONU_NUM_OK        0x8
#define HONU_INUM_OK       0x10
#define HONU_INUM_SIGN_OK  0x20

#define is_lang_nonsep_char(ch) (scheme_isalpha(ch)     \
                                 || scheme_isdigit(ch)  \
                                 || ((ch) == '-')       \
                                 || ((ch) == '+')       \
                                 || ((ch) == '_'))

#define NEXT_LINE_CHAR 0x85
#define LINE_SEPARATOR_CHAR 0x2028
#define PARAGRAPH_SEPARATOR_CHAR 0x2029
#define is_line_comment_end(ch) ((ch == '\n') || (ch == '\r') \
                                 || (ch == NEXT_LINE_CHAR) \
                                 || (ch == LINE_SEPARATOR_CHAR) \
                                 || (ch == PARAGRAPH_SEPARATOR_CHAR))

/*========================================================================*/
/*                             initialization                             */
/*========================================================================*/

void scheme_init_read(Scheme_Env *env)
{
  REGISTER_SO(quote_symbol);
  REGISTER_SO(quasiquote_symbol);
  REGISTER_SO(unquote_symbol);
  REGISTER_SO(unquote_splicing_symbol);
  REGISTER_SO(syntax_symbol);
  REGISTER_SO(unsyntax_symbol);
  REGISTER_SO(unsyntax_splicing_symbol);
  REGISTER_SO(quasisyntax_symbol);
  REGISTER_SO(paren_shape_symbol);

  REGISTER_SO(unresolved_uninterned_symbol);
  REGISTER_SO(tainted_uninterned_symbol);
  REGISTER_SO(terminating_macro_symbol);
  REGISTER_SO(non_terminating_macro_symbol);
  REGISTER_SO(dispatch_macro_symbol);
  REGISTER_SO(builtin_fast);

  quote_symbol                  = scheme_intern_symbol("quote");
  quasiquote_symbol             = scheme_intern_symbol("quasiquote");
  unquote_symbol                = scheme_intern_symbol("unquote");
  unquote_splicing_symbol       = scheme_intern_symbol("unquote-splicing");
  syntax_symbol                 = scheme_intern_symbol("syntax");
  unsyntax_symbol               = scheme_intern_symbol("unsyntax");
  unsyntax_splicing_symbol      = scheme_intern_symbol("unsyntax-splicing");
  quasisyntax_symbol            = scheme_intern_symbol("quasisyntax");
  paren_shape_symbol            = scheme_intern_symbol("paren-shape");

  unresolved_uninterned_symbol = scheme_make_symbol("unresolved");
  tainted_uninterned_symbol    = scheme_make_symbol("tainted");
    
  terminating_macro_symbol     = scheme_intern_symbol("terminating-macro");
  non_terminating_macro_symbol = scheme_intern_symbol("non-terminating-macro");
  dispatch_macro_symbol        = scheme_intern_symbol("dispatch-macro");

  /* initialize builtin_fast */
  {
    int i; 
    builtin_fast = scheme_malloc_atomic(128);
    memset(builtin_fast, READTABLE_CONTINUING, 128);
    for (i = 0; i < 128; i++) {
      if (scheme_isspace(i))
        builtin_fast[i] = READTABLE_WHITESPACE;
    }
    builtin_fast[';']  = READTABLE_TERMINATING;
    builtin_fast['\''] = READTABLE_TERMINATING;
    builtin_fast[',']  = READTABLE_TERMINATING;
    builtin_fast['"']  = READTABLE_TERMINATING;
    builtin_fast['|']  = READTABLE_MULTIPLE_ESCAPE;
    builtin_fast['\\'] = READTABLE_SINGLE_ESCAPE;
    builtin_fast['(']  = READTABLE_TERMINATING;
    builtin_fast['[']  = READTABLE_TERMINATING;
    builtin_fast['{']  = READTABLE_TERMINATING;
    builtin_fast[')']  = READTABLE_TERMINATING;
    builtin_fast[']']  = READTABLE_TERMINATING;
    builtin_fast['}']  = READTABLE_TERMINATING;
  }

  /* initialize cpt_branch */
  {
    int i;

    for (i = 0; i < 256; i++) {
      cpt_branch[i] = i;
    }

#define FILL_IN(v) \
    for (i = CPT_ ## v ## _START; i < CPT_ ## v ## _END; i++) { \
      cpt_branch[i] = CPT_ ## v ## _START; \
    }
    FILL_IN(SMALL_NUMBER);
    FILL_IN(SMALL_SYMBOL);
    FILL_IN(SMALL_MARSHALLED);
    FILL_IN(SMALL_LIST);
    FILL_IN(SMALL_PROPER_LIST);
    FILL_IN(SMALL_LOCAL);
    FILL_IN(SMALL_LOCAL_UNBOX);
    FILL_IN(SMALL_SVECTOR);
    FILL_IN(SMALL_APPLICATION);

    /* These two are handled specially: */
    cpt_branch[CPT_SMALL_APPLICATION2] = CPT_SMALL_APPLICATION2;
    cpt_branch[CPT_SMALL_APPLICATION3] = CPT_SMALL_APPLICATION3;
  }
  
  REGISTER_SO(honu_comma);
  REGISTER_SO(honu_semicolon);
  REGISTER_SO(honu_parens);
  REGISTER_SO(honu_braces);
  REGISTER_SO(honu_brackets);
  REGISTER_SO(honu_angles);
  REGISTER_SO(honu_angle_open);
  REGISTER_SO(honu_angle_close);

  honu_comma        = scheme_intern_symbol(",");
  honu_semicolon    = scheme_intern_symbol(";");
  honu_parens       = scheme_intern_symbol("#%parens");
  honu_braces       = scheme_intern_symbol("#%braces");
  honu_brackets     = scheme_intern_symbol("#%brackets");
  honu_angles       = scheme_intern_symbol("#%angles");
  honu_angle_open   = scheme_make_symbol("<"); /* uninterned */
  honu_angle_close  = scheme_make_symbol(">"); /* uninterned */

  {
    int i;
    for (i = 0; i < 128; i++) {
      delim[i] = SCHEME_OK;
    }
    for (i = 'A'; i <= 'Z'; i++) {
      delim[i] |= HONU_OK;
      delim[i + ('a'-'A')] |= HONU_OK;
    }
    for (i = '0'; i <= '9'; i++) {
      delim[i] |= (HONU_OK | HONU_NUM_OK);
    }
    delim['('] -= SCHEME_OK;
    delim[')'] -= SCHEME_OK;
    delim['['] -= SCHEME_OK;
    delim[']'] -= SCHEME_OK;
    delim['{'] -= SCHEME_OK;
    delim['}'] -= SCHEME_OK;
    delim['"'] -= SCHEME_OK;
    delim['\''] -= SCHEME_OK;
    delim[','] -= SCHEME_OK;
    delim[';'] -= SCHEME_OK;
    delim['`'] -= SCHEME_OK;
    delim['_'] |= HONU_OK;
    {
      GC_CAN_IGNORE const char *syms = "+-=?:<>.!%^&*/~|";
      for (i = 0; syms[i]; i++) {
	delim[(int)syms[i]] |= HONU_SYM_OK;
      }
    }
    delim['.'] |= HONU_NUM_OK;
    delim['e'] |= HONU_INUM_OK;
    delim['E'] |= HONU_INUM_OK;
    delim['d'] |= HONU_INUM_OK;
    delim['D'] |= HONU_INUM_OK;
    delim['f'] |= HONU_INUM_OK;
    delim['F'] |= HONU_INUM_OK;
    delim['+'] |= HONU_INUM_SIGN_OK;
    delim['-'] |= HONU_INUM_SIGN_OK;
  }

#ifdef MZ_PRECISE_GC
  register_traversers();
#endif

  GLOBAL_PARAMETER("current-readtable",             current_readtable,      MZCONFIG_READTABLE,                   env);
  GLOBAL_PARAMETER("current-reader-guard",          current_reader_guard,   MZCONFIG_READER_GUARD,                env);
  GLOBAL_PARAMETER("read-case-sensitive",           read_case_sensitive,    MZCONFIG_CASE_SENS,                   env);
  GLOBAL_PARAMETER("read-square-bracket-as-paren",  read_bracket_as_paren,  MZCONFIG_SQUARE_BRACKETS_ARE_PARENS,  env);
  GLOBAL_PARAMETER("read-curly-brace-as-paren",     read_brace_as_paren,    MZCONFIG_CURLY_BRACES_ARE_PARENS,     env);
  GLOBAL_PARAMETER("read-accept-graph",             read_accept_graph,      MZCONFIG_CAN_READ_GRAPH,              env);
  GLOBAL_PARAMETER("read-accept-compiled",          read_accept_compiled,   MZCONFIG_CAN_READ_COMPILED,           env);
  GLOBAL_PARAMETER("read-accept-box",               read_accept_box,        MZCONFIG_CAN_READ_BOX,                env);
  GLOBAL_PARAMETER("read-accept-bar-quote",         read_accept_pipe_quote, MZCONFIG_CAN_READ_PIPE_QUOTE,         env);
  GLOBAL_PARAMETER("read-decimal-as-inexact",       read_decimal_as_inexact,MZCONFIG_READ_DECIMAL_INEXACT,        env);
  GLOBAL_PARAMETER("read-accept-dot",               read_accept_dot,        MZCONFIG_CAN_READ_DOT,                env);
  GLOBAL_PARAMETER("read-accept-infix-dot",         read_accept_infix_dot,  MZCONFIG_CAN_READ_INFIX_DOT,          env);
  GLOBAL_PARAMETER("read-accept-quasiquote",        read_accept_quasi,      MZCONFIG_CAN_READ_QUASI,              env);
  GLOBAL_PARAMETER("read-accept-reader",            read_accept_reader,     MZCONFIG_CAN_READ_READER,             env);
  GLOBAL_PARAMETER("read-accept-lang",              read_accept_lang,       MZCONFIG_CAN_READ_LANG,               env);
#ifdef LOAD_ON_DEMAND
  GLOBAL_PARAMETER("read-on-demand-source",         read_delay_load,        MZCONFIG_DELAY_LOAD_INFO,             env);
#endif
  GLOBAL_PARAMETER("print-graph",                   print_graph,            MZCONFIG_PRINT_GRAPH,                 env);
  GLOBAL_PARAMETER("print-struct",                  print_struct,           MZCONFIG_PRINT_STRUCT,                env);
  GLOBAL_PARAMETER("print-box",                     print_box,              MZCONFIG_PRINT_BOX,                   env);
  GLOBAL_PARAMETER("print-vector-length",           print_vec_shorthand,    MZCONFIG_PRINT_VEC_SHORTHAND,         env);
  GLOBAL_PARAMETER("print-hash-table",              print_hash_table,       MZCONFIG_PRINT_HASH_TABLE,            env);
  GLOBAL_PARAMETER("print-unreadable",              print_unreadable,       MZCONFIG_PRINT_UNREADABLE,            env);
  GLOBAL_PARAMETER("print-pair-curly-braces",       print_pair_curly,       MZCONFIG_PRINT_PAIR_CURLY,            env);
  GLOBAL_PARAMETER("print-mpair-curly-braces",      print_mpair_curly,      MZCONFIG_PRINT_MPAIR_CURLY,           env);
  GLOBAL_PARAMETER("print-honu",                    print_honu,             MZCONFIG_HONU_MODE,                   env);
  GLOBAL_PARAMETER("print-syntax-width",            print_syntax_width,     MZCONFIG_PRINT_SYNTAX_WIDTH,          env);
  GLOBAL_PARAMETER("print-reader-abbreviations",    print_reader,           MZCONFIG_PRINT_READER,                env);
  GLOBAL_PARAMETER("print-boolean-long-form",       print_long_bool,        MZCONFIG_PRINT_LONG_BOOLEAN,          env);
  GLOBAL_PARAMETER("print-as-expression",           print_as_qq,            MZCONFIG_PRINT_AS_QQ,                 env);

  GLOBAL_PRIM_W_ARITY("make-readtable",     make_readtable,     1, -1,      env);
  GLOBAL_FOLDING_PRIM("readtable?",         readtable_p,        1, 1, 1,    env);
  GLOBAL_PRIM_W_ARITY2("readtable-mapping", readtable_mapping,  2, 2, 3, 3, env);

  if (getenv("PLT_DELAY_FROM_ZO")) {
    use_perma_cache = 0;
  }
}

void scheme_init_variable_references_constants()
{
  REGISTER_SO(variable_references);
  variable_references = scheme_make_builtin_references_table();
}


static Scheme_Simple_Object *malloc_list_stack()
{
#ifdef MZ_PRECISE_GC
  intptr_t sz = sizeof(Scheme_Simple_Object) * NUM_CELLS_PER_STACK;
  Scheme_Simple_Object *r;

  if (sz < GC_malloc_stays_put_threshold()) {
    sz = GC_malloc_stays_put_threshold();
    while (sz % sizeof(Scheme_Simple_Object)) {
      sz++;
    }
  }

  r = (Scheme_Simple_Object *)GC_malloc_array_tagged(sz);

  /* Must set the tag on the first element: */
  r[0].iso.so.type = scheme_pair_type;
  return r;
#else
  return MALLOC_N_RT(Scheme_Simple_Object, NUM_CELLS_PER_STACK);
#endif
}

void scheme_alloc_list_stack(Scheme_Thread *p)
{
  Scheme_Simple_Object *sa;
  p->list_stack_pos = 0;
  sa = malloc_list_stack();
  p->list_stack = sa;
}

void scheme_clean_list_stack(Scheme_Thread *p)
{
  if (p->list_stack) {
    memset(p->list_stack + p->list_stack_pos, 0,
	   (NUM_CELLS_PER_STACK - p->list_stack_pos) * sizeof(Scheme_Simple_Object));
#ifdef MZ_PRECISE_GC
    if (!p->list_stack_pos) {
      /* Must set the tag on the first element: */
      p->list_stack[0].iso.so.type = scheme_pair_type;
    }
#endif
  }
}

static void track_indentation(Scheme_Object *indentation, int line, int col)
{
  if (!SCHEME_NULLP(indentation)) {
    Scheme_Indent *indt = (Scheme_Indent *)SCHEME_CAR(indentation);
    /* Already checked this line? */
    if (line > indt->last_line) {
      indt->last_line = line;
      indt->multiline = 1;
      /* At least as indented as before? */
      if (col >= indt->max_indent)
	indt->max_indent = col;
      else if (!indt->suspicious_line) {
	/* Not as indented, and no suspicious line found
	   already. Suspect that the closer should have
	   appeared earlier. */
	indt->suspicious_closer = indt->closer;
	indt->suspicious_line = line;
      }
    }
  }
}

/*========================================================================*/
/*                             parameters                                 */
/*========================================================================*/

#define DO_CHAR_PARAM(name, pos) \
  return scheme_param_config(name, scheme_make_integer(pos), argc, argv, -1, NULL, NULL, 1)

static Scheme_Object *
read_case_sensitive(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-case-sensitive", MZCONFIG_CASE_SENS);
}

static Scheme_Object *
read_bracket_as_paren(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-square-bracket-as-paren", MZCONFIG_SQUARE_BRACKETS_ARE_PARENS);
}

static Scheme_Object *
read_brace_as_paren(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-curly-brace-as-paren", MZCONFIG_CURLY_BRACES_ARE_PARENS);
}

static Scheme_Object *
read_accept_graph(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-graph", MZCONFIG_CAN_READ_GRAPH);
}

static Scheme_Object *
read_accept_compiled(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-compiled", MZCONFIG_CAN_READ_COMPILED);
}

static Scheme_Object *
read_accept_box(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-box", MZCONFIG_CAN_READ_BOX);
}

static Scheme_Object *
read_accept_pipe_quote(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-pipe-quote", MZCONFIG_CAN_READ_PIPE_QUOTE);
}

static Scheme_Object *
read_decimal_as_inexact(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-decimal-as-inexact", MZCONFIG_READ_DECIMAL_INEXACT);
}

static Scheme_Object *
read_accept_dot(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-dot", MZCONFIG_CAN_READ_DOT);
}

static Scheme_Object *
read_accept_infix_dot(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-infix-dot", MZCONFIG_CAN_READ_INFIX_DOT);
}

static Scheme_Object *
read_accept_quasi(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-quasiquote", MZCONFIG_CAN_READ_QUASI);
}

static Scheme_Object *
read_accept_reader(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-reader", MZCONFIG_CAN_READ_READER);
}

static Scheme_Object *
read_accept_lang(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("read-accept-lang", MZCONFIG_CAN_READ_LANG);
}

static Scheme_Object *
print_graph(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-graph", MZCONFIG_PRINT_GRAPH);
}

static Scheme_Object *
print_struct(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-struct", MZCONFIG_PRINT_STRUCT);
}

static Scheme_Object *
print_box(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-box", MZCONFIG_PRINT_BOX);
}

static Scheme_Object *
print_vec_shorthand(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-vector-length", MZCONFIG_PRINT_VEC_SHORTHAND);
}

static Scheme_Object *
print_hash_table(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-hash-table", MZCONFIG_PRINT_HASH_TABLE);
}

static Scheme_Object *
print_unreadable(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-unreadable", MZCONFIG_PRINT_UNREADABLE);
}

static Scheme_Object *
print_pair_curly(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-pair-curly", MZCONFIG_PRINT_PAIR_CURLY);
}

static Scheme_Object *
print_mpair_curly(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-mpair-curly", MZCONFIG_PRINT_MPAIR_CURLY);
}

static Scheme_Object *
print_honu(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-honu", MZCONFIG_HONU_MODE);
}

static Scheme_Object *
print_reader(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-reader-abbreviations", MZCONFIG_PRINT_READER);
}

static Scheme_Object *
print_as_qq(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-as-expression", MZCONFIG_PRINT_AS_QQ);
}

static Scheme_Object *
print_long_bool(int argc, Scheme_Object *argv[])
{
  DO_CHAR_PARAM("print-boolean-long-form", MZCONFIG_PRINT_LONG_BOOLEAN);
}

static Scheme_Object *good_syntax_width(int c, Scheme_Object **argv)
{
  int ok;

  ok = (SCHEME_INTP(argv[0]) 
	? ((SCHEME_INT_VAL(argv[0]) > 3)
           || !SCHEME_INT_VAL(argv[0]))
	: (SCHEME_BIGNUMP(argv[0])
	   ? SCHEME_BIGPOS(argv[0])
	   : (SCHEME_FLTP(argv[0])
              ? MZ_IS_POS_INFINITY(SCHEME_FLT_VAL(argv[0]))
              : 0)));

  return ok ? scheme_true : scheme_false;
}

static Scheme_Object *
print_syntax_width(int argc, Scheme_Object *argv[])
{
  return scheme_param_config("print-syntax-width",
			     scheme_make_integer(MZCONFIG_PRINT_SYNTAX_WIDTH),
			     argc, argv,
			     -1, good_syntax_width, "+inf.0, 0, or exact integer greater than three", 0);
}

#ifdef LOAD_ON_DEMAND
static Scheme_Object *rdl_check(int argc, Scheme_Object **argv)
{
  return argv[0];
}

static Scheme_Object *
read_delay_load(int argc, Scheme_Object *argv[])
{
  return scheme_param_config("read-on-demand-source",
			     scheme_make_integer(MZCONFIG_DELAY_LOAD_INFO),
			     argc, argv,
			     -1, rdl_check, 
			     "complete path or string, optionally paired with an exact integer", 1);

}
#endif

/*========================================================================*/
/*                             main read loop                             */
/*========================================================================*/

#ifdef DO_STACK_CHECK

static Scheme_Object *read_inner_inner(Scheme_Object *port,
				       Scheme_Object *stxsrc,
				       Scheme_Hash_Table **ht,
				       Scheme_Object *indentation,
				       ReadParams *params,
				       int comment_mode,
				       int pre_char,
				       Readtable *init_readtable,
                                       int get_info);
static Scheme_Object *read_inner(Scheme_Object *port, 
				 Scheme_Object *stxsrc, 
				 Scheme_Hash_Table **ht,
				 Scheme_Object *indentation, 
				 ReadParams *params,
				 int comment_mode);

static void set_need_copy(Scheme_Hash_Table **ht)
{
  /* Set indicator in *ht that we need to copy: */
  if (!*ht) {
    Scheme_Hash_Table *tht;
    tht = scheme_make_hash_table(SCHEME_hash_ptr);
    *ht = tht;
  }
  scheme_hash_set(*ht, tainted_uninterned_symbol, scheme_true);
}

static Scheme_Object *read_inner_inner_k(void)
{
  Scheme_Thread *p = scheme_current_thread;
  Scheme_Object *o = (Scheme_Object *)p->ku.k.p1;
  Scheme_Hash_Table **ht = (Scheme_Hash_Table **)p->ku.k.p2;
  Scheme_Object *stxsrc = (Scheme_Object *)p->ku.k.p3;
  Scheme_Object *indentation = SCHEME_CAR((Scheme_Object *)p->ku.k.p4);
  ReadParams *params = (ReadParams *)SCHEME_CDR((Scheme_Object *)p->ku.k.p4);
  Readtable *table = (Readtable *)p->ku.k.p5;

  p->ku.k.p1 = NULL;
  p->ku.k.p2 = NULL;
  p->ku.k.p3 = NULL;
  p->ku.k.p4 = NULL;
  p->ku.k.p5 = NULL;

  return read_inner_inner(o, stxsrc, ht, indentation, params, p->ku.k.i1, p->ku.k.i2, table, p->ku.k.i3);
}
#endif

#define MAX_GRAPH_ID_DIGITS 8

static Scheme_Object *
read_inner_inner(Scheme_Object *port, Scheme_Object *stxsrc, Scheme_Hash_Table **ht,
		 Scheme_Object *indentation, ReadParams *params,
		 int comment_mode, int pre_char, Readtable *table,
                 int get_info)
{
  int ch, ch2, depth, dispatch_ch, special_value_need_copy = 0;
  intptr_t line = 0, col = 0, pos = 0;
  Scheme_Object *special_value;

#ifdef DO_STACK_CHECK
  {
# include "mzstkchk.h"
    {
      Scheme_Thread *p = scheme_current_thread;
      Scheme_Object *pr;
      ReadParams *params2;

      /* params may be on the stack, so move it to the heap: */
      params2 = MALLOC_ONE_RT(ReadParams);
      memcpy(params2, params, sizeof(ReadParams));
#ifdef MZ_PRECISE_GC
      params2->type = scheme_rt_read_params;
#endif

      p->ku.k.p1 = (void *)port;
      p->ku.k.p2 = (void *)ht;
      p->ku.k.p3 = (void *)stxsrc;

      pr = scheme_make_pair(indentation, (Scheme_Object *)params2);
      p->ku.k.p4 = (void *)pr;

      p->ku.k.p5 = (void *)table;

      p->ku.k.i1 = comment_mode;
      p->ku.k.i2 = pre_char;
      p->ku.k.i3 = get_info;
      return scheme_handle_stack_overflow(read_inner_inner_k);
    }
  }
#endif

 start_over:

  SCHEME_USE_FUEL(1);

  while (1) {
    if (pre_char >= 0) {
      ch = pre_char;
      pre_char = -1;
    } else
      ch = scheme_getc_special_ok(port);
    if (NOT_EOF_OR_SPECIAL(ch)) {
      if (table) {
	if (!(readtable_kind(table, ch, params) & READTABLE_WHITESPACE))
	  break;
      } else if (!scheme_isspace(ch))
	break;
    } else
      break;
  }

 start_over_with_ch:

  scheme_tell_all(port, &line, &col, &pos);

  /* Found non-whitespace. Track indentation: */
  if (col >= 0) {
    if (SCHEME_PAIRP(indentation)) {
      int effective_ch;
      effective_ch = readtable_effective_char(table, ch);
      /* Ignore if it's a comment start or spurious closer: */
      if ((effective_ch != ';')
	  && !((effective_ch == '#') && (scheme_peekc_special_ok(port) == '|'))
	  && (effective_ch != ')')
	  && ((effective_ch != '}') || !params->curly_braces_are_parens)
	  && ((effective_ch != ']') || !params->square_brackets_are_parens)) {
	track_indentation(indentation, line, col);
      }
    }
  }

  special_value = NULL;
  if (table && NOT_EOF_OR_SPECIAL(ch)) {
    Scheme_Object *v;
    int use_default, ch2 = ch;
    v = readtable_handle(table, &ch2, &use_default, params,
			 port, stxsrc, line, col, pos, ht);
    if (!use_default) {
      dispatch_ch = SCHEME_SPECIAL;
      special_value = v;
    } else
      dispatch_ch = ch2;
  } else
    dispatch_ch = ch;

  if (get_info && (dispatch_ch != '#') && (dispatch_ch != ';')) {
    /* If ch is EOF, then col or pos wasn't incremented by reading ch.
       The col and pos might be used in an error message, which expects
       to subtract one from each --- so counteract by adding one here. */
    if (ch == EOF) {
      if (pos >= 0) pos++;
      if (col >= 0) col++;
    }
    return expected_lang("", ch, port, stxsrc, line, col, pos, get_info);
  }

  switch ( dispatch_ch )
    {
    case EOF: 
      return scheme_eof;
    case SCHEME_SPECIAL:
      {
	if (!special_value) {
	  special_value = scheme_get_special(port, stxsrc, line, col, pos, 0, ht);
	  special_value_need_copy = 1;
	}
	break;
      }
    case ']':
      if (!params->square_brackets_are_parens) {
	scheme_read_err(port, stxsrc, line, col, pos, 1, 0, indentation, "read: illegal use of close square bracket");
	return NULL;
      } else {
	unexpected_closer(ch, port, stxsrc, line, col, pos, indentation, params);
	return NULL;
      }
    case '}':
      if (!params->curly_braces_are_parens) {
	scheme_read_err(port, stxsrc, line, col, pos, 1, 0, indentation, "read: illegal use of close curly brace");
	return NULL;
      } else {
	unexpected_closer(ch, port, stxsrc, line, col, pos, indentation, params);
	return NULL;
      }
    case ')':
      unexpected_closer(ch, port, stxsrc, line, col, pos, indentation, params);
      return NULL;
    case '(':
      return read_list(port, stxsrc, line, col, pos, ch, ')', mz_shape_cons, 0, ht, indentation, params);
    case '[':
      if (!params->square_brackets_are_parens) {
	scheme_read_err(port, stxsrc, line, col, pos, 1, 0, indentation, "read: illegal use of open square bracket");
	return NULL;
      } else
	return read_list(port, stxsrc, line, col, pos, ch, ']', mz_shape_cons, 0, ht, indentation, params);
    case '{':
      if (!params->curly_braces_are_parens) {
	scheme_read_err(port, stxsrc, line, col, pos, 1, 0, indentation, "read: illegal use of open curly brace");
	return NULL;
      } else
	return read_list(port, stxsrc, line, col, pos, ch, '}', mz_shape_cons, 0, ht, indentation, params);
    case '|':
      special_value = read_symbol(ch, 1, port, stxsrc, line, col, pos, ht, indentation, params, table);
      break;
    case '"':
      return read_string(0, 0, port, stxsrc, line, col, pos, ht, indentation, params, 1);
    case '\'':
      if (params->honu_mode) {
	return read_string(0, 1, port, stxsrc, line, col, pos, ht, indentation, params, 1);
      } else {
	return read_quote("quoting '", quote_symbol, 1, port, stxsrc, line, col, pos, ht, indentation, params);
      }
    case '`':
      if (params->honu_mode) {
	/* Raises illegal-char error: */
	return read_symbol(ch, 1, port, stxsrc, line, col, pos, ht, indentation, params, table);
      } else if (!params->can_read_quasi) {
	scheme_read_err(port, stxsrc, line, col, pos, 1, 0, indentation, "read: illegal use of backquote");
	return NULL;
      } else
	return read_quote("quasiquoting `", quasiquote_symbol, 1, port, stxsrc, line, col, pos, ht, indentation, params);
    case ',':
      if (params->honu_mode) {
	if (stxsrc)
	  return scheme_make_stx_w_offset(honu_comma, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
	else
	  return honu_comma;
      } else if (!params->can_read_quasi) {
	scheme_read_err(port, stxsrc, line, col, pos, 1, 0, indentation, "read: illegal use of comma");
	return NULL;
      } else {
	if (scheme_peekc_special_ok(port) == '@') {
	  ch = scheme_getc(port); /* must be '@' */
	  return read_quote("unquoting ,@", unquote_splicing_symbol, 2, port, stxsrc, line, col, pos, ht, indentation, params);
	} else
	  return read_quote("unquoting ,", unquote_symbol, 1, port, stxsrc, line, col, pos, ht, indentation, params);
      }
    case ';':
      if (params->honu_mode) {
	if (stxsrc)
	  return scheme_make_stx_w_offset(honu_semicolon, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
	else
	  return honu_semicolon;
      } else {
	while (((ch = scheme_getc_special_ok(port)) != '\n') 
               && !is_line_comment_end(ch)) {
	  if (ch == EOF) {
            if (comment_mode & RETURN_FOR_COMMENT)
              return NULL;
            if (get_info)
              return expected_lang("", ch, port, stxsrc, line, col, pos, get_info);
	    return scheme_eof;
          }
	  if (ch == SCHEME_SPECIAL)
	    scheme_get_ready_read_special(port, stxsrc, ht);
	}
	if ((table && (comment_mode & RETURN_FOR_SPECIAL_COMMENT))
	    || (comment_mode & RETURN_FOR_COMMENT))
	  return NULL;
	goto start_over;
      }
    case '+':
    case '-':
      if (params->honu_mode) {
	special_value = read_symbol(ch, 1, port, stxsrc, line, col, pos, ht, indentation, params, table);
	break;
      }
    case '.': /* ^^^ fallthrough ^^^ */
      ch2 = scheme_peekc_special_ok(port);
      if ((NOT_EOF_OR_SPECIAL(ch2) && isdigit_ascii(ch2)) || (ch2 == '.')
	  || (!params->honu_mode
	      && ((ch2 == 'i') || (ch2 == 'I') /* Maybe inf */
		  || (ch2 == 'n') || (ch2 == 'N') /* Maybe nan*/ ))) {
	/* read_number tries to get a number, but produces a symbol if number parsing doesn't work: */
	special_value = read_number(ch, port, stxsrc, line, col, pos, 0, 0, 10, 0, ht, indentation, params, table);
      } else {
	special_value = read_symbol(ch, 0, port, stxsrc, line, col, pos, ht, indentation, params, table);
      }
      break;
    case '#':
      ch = scheme_getc_special_ok(port);

      if (get_info && (ch != '|') && (ch != '!') && (ch != 'l') && (ch != ';')) {
        return expected_lang("#", ch, port, stxsrc, line, col, pos, get_info);
      }

      if (table) {
	Scheme_Object *v;
	int use_default;
	v = readtable_handle_hash(table, ch, &use_default, params,
				  port, stxsrc, line, col, pos, ht);
	if (!use_default) {
	  if (v)
	    return v;
	  if (comment_mode & RETURN_FOR_SPECIAL_COMMENT)
	    return NULL;
	  goto start_over;
	}
      }

      special_value = NULL;

      switch (ch)
	{
	case EOF:
	case SCHEME_SPECIAL:
	  scheme_read_err(port, stxsrc, line, col, pos, 1, ch, indentation, "read: bad syntax `#'");
	  break;
	case ';':
	  {
	    Scheme_Object *skipped;
	    skipped = read_inner(port, stxsrc, ht, indentation, params, 0);
	    if (SCHEME_EOFP(skipped))
	      scheme_read_err(port, stxsrc, line, col, pos, MINSPAN(port, pos, 2), EOF, indentation,
			      "read: expected a commented-out element for `#;' (found end-of-file)");
	    /* For resolving graphs introduced in #; : */
	    if (*ht) {
	      Scheme_Object *v;
	      v = scheme_hash_get(*ht, unresolved_uninterned_symbol);
	      if (!v)
		v = scheme_null;
	      v = scheme_make_pair(skipped, v);
	      scheme_hash_set(*ht, unresolved_uninterned_symbol, v);
	    }

	    if ((comment_mode & RETURN_FOR_HASH_COMMENT)
		|| (table && (comment_mode & RETURN_FOR_SPECIAL_COMMENT))
		|| (comment_mode & RETURN_FOR_COMMENT))
	      return NULL;

	    goto start_over;
	  }
	  break;
	case '%':
	  if (!params->honu_mode) {
	    scheme_ungetc('%', port);
	    special_value = read_symbol('#', 1, port, stxsrc, line, col, pos, ht, indentation, params, table);
	  }
	  break;
	case ':':
	  if (!params->honu_mode) {
	    return read_keyword(-1, port, stxsrc, line, col, pos, ht, indentation, params, table);
	  }
	  break;
	case '(':
	  if (!params->honu_mode) {
	    return read_vector(port, stxsrc, line, col, pos, ch, ')', -1, NULL, ht, indentation, params, 0);
	  }
	  break;
	case '[':
	  if (!params->honu_mode) {
	    if (!params->square_brackets_are_parens) {
	      scheme_read_err(port, stxsrc, line, col, pos, 2, 0, indentation, "read: bad syntax `#['");
	      return NULL;
	    } else
	      return read_vector(port, stxsrc, line, col, pos, ch, ']', -1, NULL, ht, indentation, params, 0);
	  }
	  break;
	case '{':
	  if (!params->honu_mode) {
	    if (!params->curly_braces_are_parens) {
	      scheme_read_err(port, stxsrc, line, col, pos, 2, 0, indentation, "read: bad syntax `#{'");
	      return NULL;
	    } else
	      return read_vector(port, stxsrc, line, col, pos, ch, '}', -1, NULL, ht, indentation, params, 0);
	  }
	  break;
	case '\\':
	  if (!params->honu_mode) {
	    Scheme_Object *chr;
	    chr = read_character(port, stxsrc, line, col, pos, ht, indentation, params);
	    if (stxsrc)
	      chr = scheme_make_stx_w_offset(chr, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
	    return chr;
	  }
	  break;
	case 'T':
	case 't': 
          if (!params->honu_mode) {
            if (next_is_delim(port, params, 1, 1)) {
              /* found delimited `#t' */
              return (stxsrc
                      ? scheme_make_stx_w_offset(scheme_true, line, col, pos, 2, stxsrc, STX_SRCTAG)
                      : scheme_true);
            } else {
              GC_CAN_IGNORE const mzchar str[] = { 't', 'r', 'u', 'e', 0 };
              return read_delimited_constant(ch, str, scheme_true, port, stxsrc, line, col, pos, 
                                             indentation, params, table);
            }
          }
	case 'F':
	case 'f': 
          if (!params->honu_mode) {
            if (next_is_delim(port, params, 1, 1)) {
              /* found delimited `#f' */
              return (stxsrc
                      ? scheme_make_stx_w_offset(scheme_false, line, col, pos, 2, stxsrc, STX_SRCTAG)
                      : scheme_false);
            } else {
              GC_CAN_IGNORE const mzchar str[] = { 'f', 'a', 'l', 's', 'e', 0 };
              return read_delimited_constant(ch, str, scheme_false, port, stxsrc, line, col, pos, 
                                             indentation, params, table);
            }
          }
	case 'c':
	case 'C':
	  if (!params->honu_mode) {
	    Scheme_Object *v;
	    int sens = 0;
	    int save_sens;

	    ch = scheme_getc_special_ok(port);
	    switch ( ch ) {
	    case 'i':
	    case 'I':
	      sens = 0;
	      break;
	    case 's':
	    case 'S':
	      sens = 1;
	      break;
	    default:
	      scheme_read_err(port, stxsrc, line, col, pos, 2, ch, indentation,
			      "read: expected `s' or `i' after #c");
	      return NULL;
	    }


	    save_sens = params->case_sensitive;
	    params->case_sensitive = sens;
	    
	    v = read_inner(port, stxsrc, ht, indentation, params, 0);
	    
	    params->case_sensitive = save_sens;
	    
	    if (SCHEME_EOFP(v)) {
	      scheme_read_err(port, stxsrc, line, col, pos, 2, EOF, indentation,
			      "read: end-of-file after #c%c",
			      sens ? 's' : 'i');
	      return NULL;
	    }

	    return v;
	  }
	  break;
	case 's':
	case 'S':
          {
            int orig_ch = ch, effective_ch;
            ch = scheme_getc_special_ok(port);
            if (NOT_EOF_OR_SPECIAL(ch))
              effective_ch = readtable_effective_char(params->table, ch);
            else
              effective_ch = ch;
            if ((orig_ch == 's') 
                && ((effective_ch == '(')
                    || (effective_ch == '[' && params->square_brackets_are_parens)
                    || (effective_ch == '{' && params->curly_braces_are_parens))) {
              Scheme_Object *v;
              Scheme_Struct_Type *st;
              
              if (effective_ch == '(')
                ch = ')';
              else if (effective_ch == '[')
                ch = ']';
              else if (effective_ch == '{')
                ch = '}';

              v = read_vector(port, stxsrc, line, col, pos, orig_ch, ch, -1, NULL, ht, indentation, params, 1);
              if (stxsrc)
                v = SCHEME_STX_VAL(v);

              if (SCHEME_VEC_SIZE(v)) {
                Scheme_Object *key;
                key = SCHEME_VEC_ELS(v)[0];
                if (stxsrc)
                  key = scheme_syntax_to_datum(key, 0, NULL);
                st = scheme_lookup_prefab_type(key, SCHEME_VEC_SIZE(v) - 1);
              } else
                st = NULL;

              if (!st || (st->num_slots != (SCHEME_VEC_SIZE(v) - 1))) {
                scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
                                (SCHEME_VEC_SIZE(v)
                                 ? (st
                                    ? ("read: mismatch between structure description"
                                       " and number of provided field values in `#s' form")
                                    : "read: invalid structure description in `#s' form")
                                 : "read: missing structure description in `#s' form"));
                return NULL;
              }

              if (stxsrc && !(MZ_OPT_HASH_KEY(&st->iso) & STRUCT_TYPE_ALL_IMMUTABLE)) {
                scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
                                "read: cannot read mutable `#s' form as syntax");
              }

              v = scheme_make_prefab_struct_instance(st, v);

              if (stxsrc)
                v = scheme_make_stx_w_offset(v, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);

              return v;
            } else if ((ch == 'x') || (ch == 'X')) {
              ReadParams params_copy;
              Scheme_Object *v;

              memcpy(&params_copy, params, sizeof(ReadParams));
              params_copy.honu_mode = 0;

              v = read_inner(port, stxsrc, ht, indentation, &params_copy, 0);

              if (SCHEME_EOFP(v)) {
                scheme_read_err(port, stxsrc, line, col, pos, 2, EOF, indentation,
                                "read: end-of-file after #sx");
                return NULL;
              }

              return v;
            } else {
              scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation,
                              "read: expected `x'%s after `#%c'",
                              (orig_ch == 's' ? "or `('" : ""),
                              orig_ch);
              return NULL;
            }
          }
	case 'X':
	case 'x': 
	  if (!params->honu_mode) {
	    return read_number(-1, port, stxsrc, line, col, pos, 0, 0, 16, 1, ht, indentation, params, table);
	  }
	  break;
	case 'B':
	case 'b': 
	  if (!params->honu_mode) {
	    return read_number(-1, port, stxsrc, line, col, pos, 0, 0, 2, 1, ht, indentation, params, table);
	  }
	  break;
	case 'O':
	case 'o': 
	  if (!params->honu_mode) {
	    return read_number(-1, port, stxsrc, line, col, pos, 0, 0, 8, 1, ht, indentation, params, table);
	  }
	  break;
	case 'D':
	case 'd': 
	  if (!params->honu_mode) {
	    return read_number(-1, port, stxsrc, line, col, pos, 0, 0, 10, 1, ht, indentation, params, table);
	  }
	  break;
	case 'E':
	case 'e': 
	  if (!params->honu_mode) {
            return read_number(-1, port, stxsrc, line, col, pos, 0, 1, 10, 0, ht, indentation, params, table);
	  }
	  break;
	case 'I':
	case 'i': 
	  if (!params->honu_mode) {
	    return read_number(-1, port, stxsrc, line, col, pos, 1, 0, 10, 0, ht, indentation, params, table);
	  }
	  break;
	case '\'':
	  if (!params->honu_mode) {
	    return read_quote("quoting #'", syntax_symbol, 2, port, stxsrc, line, col, pos, ht, indentation, params);
	  }
	  break;
	case '`':
	  if (!params->honu_mode) {
	    return read_quote("quasiquoting #`", quasisyntax_symbol, 2, port, stxsrc, line, col, pos, ht, indentation, params);
	  }
	  break;
	case ',':
	  if (!params->honu_mode) {
	    if (scheme_peekc_special_ok(port) == '@') {
	      ch = scheme_getc(port); /* must be '@' */
	      return read_quote("unquoting #`@", unsyntax_splicing_symbol, 3, port, stxsrc, line, col, pos, ht, indentation, params);
	    } else
	      return read_quote("unquoting #`", unsyntax_symbol, 2, port, stxsrc, line, col, pos, ht, indentation, params);
	  }
	  break;
	case '~':
	  if (!params->honu_mode) {
	    if (params->can_read_compiled) {
	      Scheme_Object *cpld;
	      cpld = read_compiled(port, stxsrc, line, col, pos, ht, params);
	      if (stxsrc)
		cpld = scheme_make_stx_w_offset(cpld, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
	      return cpld;
	    } else {
	      scheme_read_err(port, stxsrc, line, col, pos, 2, 0, indentation,
			      "read: #~ compiled expressions" NOT_ENABLED_str);
	      return NULL;
	    }
	  }
	  break;
        case '^':
          if (params->read_relative_path) {
            ch = scheme_getc_special_ok(port);
            if (ch == '#') {
              ch = scheme_getc_special_ok(port);
              if (ch == '"') {
                Scheme_Object *str;
                intptr_t sline = 0, scol = 0, spos = 0;

		scheme_tell_all(port, &sline, &scol, &spos);

                str = read_string(1, 0, port, stxsrc, sline, scol, spos, ht, indentation, params, 1);

                str->type = SCHEME_PLATFORM_PATH_KIND;

                if (scheme_is_relative_path(SCHEME_PATH_VAL(str), SCHEME_PATH_LEN(str), SCHEME_PLATFORM_PATH_KIND)) {
                  if (SCHEME_PATHP(params->read_relative_path)) {
                    Scheme_Object *a[2];
                    a[0] = params->read_relative_path;
                    a[1] = str;
                    str = scheme_build_path(2, a);
                  }
                }

                return str;
              }
            } else {
              scheme_read_err(port, stxsrc, line, col, pos, 2, ch, indentation,
                              "read: bad syntax `#^#%c'",
                              ch);
            }
          } else {
            scheme_read_err(port, stxsrc, line, col, pos, 2, ch, indentation,
                            "read: bad syntax `#^%c'",
                            ch);
          }
          break;
	case '|':
	  if (!params->honu_mode) {
	    /* FIXME: integer overflow possible */
	    depth = 0;
	    ch2 = 0;
	    do {
	      ch = scheme_getc_special_ok(port);

	      if (ch == EOF)
		scheme_read_err(port, stxsrc, line, col, pos, MINSPAN(port, pos, 2), EOF, indentation,
				"read: end of file in #| comment");
	      else if (ch == SCHEME_SPECIAL)
		scheme_get_ready_read_special(port, stxsrc, ht);

	      if ((ch2 == '|') && (ch == '#')) {
		if (!(depth--)) {
		  if ((table && (comment_mode & RETURN_FOR_SPECIAL_COMMENT))
		      || (comment_mode & RETURN_FOR_COMMENT))
		    return NULL;
		  goto start_over;
		}
		ch = 0; /* So we don't count '#' toward an opening "#|" */
	      } else if ((ch2 == '#') && (ch == '|')) {
		depth++;
		ch = 0; /* So we don't count '|' toward a closing "|#" */
	      }
	      ch2 = ch;
	    } while (1);
	  }
	  break;
	case '&':
	  if (!params->honu_mode) {
	    if (params->can_read_box)
	      return read_box(port, stxsrc, line, col, pos, ht, indentation, params);
	    else {
	      scheme_read_err(port, stxsrc, line, col, pos, 2, 0, indentation,
			      "read: #& expressions" NOT_ENABLED_str);
	      return NULL;
	    }
	  }
	  break;
        case 'l':
          {
            mzchar found[5];
            int fl = 1;
            found[0] = 'l';
            ch = scheme_getc_special_ok(port);
            found[fl++] = ch;
	    if (ch == 'a') {
              ch = scheme_getc_special_ok(port);
              found[fl++] = ch;
              if (ch == 'n') {
                ch = scheme_getc_special_ok(port);
                found[fl++] = ch;
                if (ch == 'g') {
                  ch = scheme_getc_special_ok(port);
                  found[fl++] = ch;
                  if (ch == ' ') {
                    /* #lang */
                    Scheme_Object *v;
                    if (!params->can_read_reader
                        || !params->can_read_lang) {
                      scheme_read_err(port, stxsrc, line, col, pos, 6, 0, indentation,
                                      "read: #lang" NOT_ENABLED_str);
                      return NULL;
                    }
                    v = read_lang(port, stxsrc, line, col, pos, get_info, ht, indentation, params, 0);
                    if (!v) {
                      if (comment_mode & RETURN_FOR_SPECIAL_COMMENT)
                        return NULL;
                      goto start_over;
                    }
                    return v;
                  } else {
                    if (ch == EOF) --fl;
                    scheme_read_err(port, stxsrc, line, col, pos, 6, ch, indentation,
                                    "read%s: expected a single space after `#lang'",
                                    (get_info ? "-language" : ""));
                    return NULL;
                  }
                }
              }
            }
            if (ch == EOF) --fl;
            scheme_read_err(port, stxsrc, line, col, pos, fl, ch, indentation,
                            "read%s: bad input: `#%u'",
                            (get_info ? "-language" : ""),
                            found, (intptr_t)fl);
            return NULL;
          }
          break;
	case 'r':
	case 'p':
	  if (!params->honu_mode) {
	    int orig_ch = ch;
	    int cnt = 0, is_byte = 0;
	    char *expect;

	    ch = scheme_getc_special_ok(port);
	    if (ch == 'x') {
	      expect = "x#";
	      ch = scheme_getc_special_ok(port);
	      cnt++;
	      if (ch == '#') {
		is_byte = 1;
		cnt++;
		ch = scheme_getc_special_ok(port);
	      }
	      if (ch == '"') {
		Scheme_Object *str;
		int is_err;
                intptr_t sline = 0, scol = 0, spos = 0;

		/* Skip #rx[#]: */
		scheme_tell_all(port, &sline, &scol, &spos);

		str = read_string(is_byte, 0, port, stxsrc, sline, scol, spos, ht, indentation, params, 1);

		if (stxsrc)
		  str = SCHEME_STX_VAL(str);

		str = scheme_make_regexp(str, is_byte, (orig_ch == 'p'), &is_err);

		if (is_err) {
		  scheme_read_err(port, stxsrc, sline, scol, spos, 2, 0, indentation,
				  "read: bad %sregexp string: %s", 
				  (orig_ch == 'r') ? "" : "p",
				  (char *)str);
		  return NULL;
		}

		if (stxsrc)
		  str = scheme_make_stx_w_offset(str, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);

		return str;
	      }
	    } else if ((orig_ch == 'r') && (ch == 'e')) {
	      expect = "eader";
	      cnt++;
	      while (expect[cnt]) {
		ch = scheme_getc_special_ok(port);
		if (ch != expect[cnt])
		  break;
		cnt++;
	      }
	      if (!expect[cnt]) {
		/* Found #reader. Read an S-exp. */
		Scheme_Object *v;

		if (!params->can_read_reader) {
		  scheme_read_err(port, stxsrc, line, col, pos, 7, 0, indentation,
				  "read: #reader" NOT_ENABLED_str);
		  return NULL;
		}

		v = read_reader(port, stxsrc, line, col, pos, ht, indentation, params);
		if (!v) {
		  if (comment_mode & RETURN_FOR_SPECIAL_COMMENT)
		    return NULL;
		  goto start_over;
		}
		return v;
	      }
	    } else
	      expect = "";

	    {
	      mzchar a[6];
	      int i;

	      for (i = 0; i < cnt; i++) {
		a[i] = expect[i];
	      }
	      if (NOT_EOF_OR_SPECIAL(ch)) {
		a[cnt++] = ch;
	      }

	      scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos),
			      ch, indentation,
			      "read: bad syntax `#%c%u'",
			      orig_ch, a, (intptr_t)cnt);
	      return NULL;
	    }
	  }
	  break;
	case 'h':
	  {
	    int honu = 0;

	    ch = scheme_getc_special_ok(port);
	    switch ( ch ) {
	    case 'a':
	      honu = 0;
	      break;
	    case 'x':
	      honu = 1;
	      break;
	    default:
	      if (!params->honu_mode) {
		scheme_read_err(port, stxsrc, line, col, pos, 2, ch, indentation,
				"read: expected `a' or `x' after #h");
		return NULL;
	      }
	      honu = 0;
	      break;
	    }

	    if (params->honu_mode && (honu != 1)) {
	      scheme_read_err(port, stxsrc, line, col, pos, 2, ch, indentation,
			      "read: expected `x' after #h");
	      return NULL;
	    }

	    if (honu) {
	      ReadParams params_copy;
	      Scheme_Object *v;

	      memcpy(&params_copy, params, sizeof(ReadParams));
	      params_copy.honu_mode = 1;

              v = read_inner(port, stxsrc, ht, indentation, &params_copy, 0);
              if (SCHEME_EOFP(v)) {
                scheme_read_err(port, stxsrc, line, col, pos, 2, EOF, indentation,
                                "read: end-of-file after #hx");
                return NULL;
              }

	      return v;
	    } else {
	      GC_CAN_IGNORE const mzchar str[] = { 's', 'h', 'e', 'q', 'v', 0 };
	      int scanpos = 0, failed = 0;

	      do {
		ch = scheme_getc_special_ok(port);
		if ((mzchar)ch == str[scanpos]) {
		  scanpos++;
		} else {
		  if ((scanpos == 2) || (scanpos == 4)) {
                    int effective_ch;
                    effective_ch = readtable_effective_char(table, ch);
		    if (!(effective_ch == '(')
			&& !(effective_ch == '[' && params->square_brackets_are_parens)
			&& !(effective_ch == '{' && params->curly_braces_are_parens))
		      failed = 1;
		  } else
		    failed = 1;
		  break;
		}
	      } while (str[scanpos]);
              
	      if (!failed) {
		/* Found recognized tag. Look for open paren... */
                int effective_ch, kind;

		if (scanpos > 4)
		  ch = scheme_getc_special_ok(port);
                
                effective_ch = readtable_effective_char(table, ch);

                if (scanpos == 4)
                  kind = 0;
                else if (scanpos == 2)
                  kind = 1;
                else 
                  kind = 2;

		if (effective_ch == '(')
		  return read_hash(port, stxsrc, line, col, pos, ch, ')', kind, ht, indentation, params);
		if (effective_ch == '[' && params->square_brackets_are_parens)
		  return read_hash(port, stxsrc, line, col, pos, ch, ']', kind, ht, indentation, params);
		if (effective_ch == '{' && params->curly_braces_are_parens)
		  return read_hash(port, stxsrc, line, col, pos, ch, '}', kind, ht, indentation, params);
	      }

	      /* Report an error. So far, we read 'ha', then scanpos chars of str, then ch. */
	      {
		mzchar str_part[7], one_more[2];

		memcpy(str_part, str, scanpos * sizeof(mzchar));
		str_part[scanpos] = 0;
		if (NOT_EOF_OR_SPECIAL(ch)) {
		  one_more[0] = ch;
		  one_more[1] = 0;
		} else
		  one_more[0] = 0;

		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos),
				ch, indentation,
				"read: bad syntax `#ha%5%u'",
				str_part,
				one_more, (intptr_t)(NOT_EOF_OR_SPECIAL(ch) ? 1 : 0));
		return NULL;
	      }
	    }
	  }
	  break;
	case '"':
	  if (!params->honu_mode) {
	    return read_string(1, 0, port, stxsrc, line, col, pos, ht, indentation, params, 1);
	  }
	  break;
	case '<':
	  if (!params->honu_mode) {
	    if (scheme_peekc_special_ok(port) == '<') {
	      /* Here-string */
	      ch = scheme_getc_special_ok(port);
	      return read_here_string(port, stxsrc, line, col, pos,indentation, params);
	    } else {
	      scheme_read_err(port, stxsrc, line, col, pos, 2, 0, indentation, "read: bad syntax `#<'");
	      return NULL;
	    }
	  }
	  break;
        case '!':
          ch = scheme_getc_special_ok(port);
          if ((ch == ' ') || (ch == '/')) {
            /* line comment, with '\' as a continuation */
            int was_backslash = 0, was_backslash_cr = 0, prev_backslash_cr;
            while(1) {
              prev_backslash_cr = was_backslash_cr;
              was_backslash_cr = 0;
              ch = scheme_getc_special_ok(port);
              if (ch == EOF) {
                break;
              } else if (ch == SCHEME_SPECIAL) {
		scheme_get_ready_read_special(port, stxsrc, ht);
              } else if (ch == '\r') {
                if (was_backslash) {
                  was_backslash_cr = 1;
                } else
                  break;
              } else if (ch == '\n') {
                if (!was_backslash && !was_backslash_cr)
                  break;
              }
              was_backslash = (ch == '\\');
            }
            if (comment_mode & RETURN_FOR_COMMENT)
              return NULL;
            goto start_over;
          } else if ((ch < 128) && is_lang_nonsep_char(ch)) {
            Scheme_Object *v;
            if (!params->can_read_reader
                || !params->can_read_lang) {
              scheme_read_err(port, stxsrc, line, col, pos, 2, 0, indentation,
                              "read: #!" NOT_ENABLED_str);
              return NULL;
            }
            v = read_lang(port, stxsrc, line, col, pos, get_info, ht, indentation, params, ch);
            if (!v) {
              if (comment_mode & RETURN_FOR_SPECIAL_COMMENT)
                return NULL;
              goto start_over;
            }
            return v;
          } else {
            if (NOT_EOF_OR_SPECIAL(ch))
              scheme_read_err(port, stxsrc, line, col, pos, 3, 
                              ch, indentation, "read: bad syntax `#!%c'", ch);
            else
              scheme_read_err(port, stxsrc, line, col, pos, 2, 
                              ch, indentation, "read: bad syntax `#!'", ch);
            return NULL;
          }
          break;
	default:
	  if (!params->honu_mode) {
	    int vector_length = -1;
	    int i = 0, j = 0, overflow = 0, digits = 0, effective_ch;
	    mzchar tagbuf[64], vecbuf[64]; /* just for errors */

	    while (NOT_EOF_OR_SPECIAL(ch) && isdigit_ascii(ch)) {
	      if (digits <= MAX_GRAPH_ID_DIGITS)
		digits++;

	      /* For vector error msgs, want to drop leading zeros: */
	      if (j || (ch != '0')) {
		if (j < 60) {
		  vecbuf[j++] = ch;
		} else if (j == 60) {
		  vecbuf[j++] = '.';
		  vecbuf[j++] = '.';
		  vecbuf[j++] = '.';
		  vecbuf[j] = 0;
		}
	      }

	      /* For tag error msgs, want to keep zeros: */
	      if (i < 60) {
		tagbuf[i++] = ch;
	      } else if (i == 60) {
		tagbuf[i++] = '.';
		tagbuf[i++] = '.';
		tagbuf[i++] = '.';
		tagbuf[i] = 0;
	      }

	      if (!overflow) {
		intptr_t old_len;

		if (vector_length < 0)
		  vector_length = 0;

		old_len = vector_length;
		vector_length = (vector_length * 10) + (ch - 48);
		if ((vector_length < 0)|| ((vector_length / 10) != old_len)) {
		  overflow = 1;
		}
	      }
	      ch = scheme_getc_special_ok(port);
	    }

	    if (overflow)
	      vector_length = -2;
	    vecbuf[j] = 0;
	    tagbuf[i] = 0;

            effective_ch = readtable_effective_char(table, ch);

	    if (effective_ch == '(')
	      return read_vector(port, stxsrc, line, col, pos, ch, ')', vector_length, vecbuf, ht, indentation, params, 0);
	    if (effective_ch == '[' && params->square_brackets_are_parens)
	      return read_vector(port, stxsrc, line, col, pos, ch, ']', vector_length, vecbuf, ht, indentation, params, 0);
	    if (effective_ch == '{' && params->curly_braces_are_parens)
	      return read_vector(port, stxsrc, line, col, pos, ch, '}', vector_length, vecbuf, ht, indentation, params, 0);

	    if (ch == '#' && (vector_length != -1)) {
	      /* Not a vector after all: a graph reference */
	      Scheme_Object *ph;

	      if (stxsrc)
		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				"read: #..# expressions not allowed in read-syntax mode");

	      if (!params->can_read_graph)
		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				"read: #..# expressions" NOT_ENABLED_str);

	      if (digits > MAX_GRAPH_ID_DIGITS)
		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				"read: graph id too long in #%5#",
				tagbuf);

	      if (*ht)
		ph = (Scheme_Object *)scheme_hash_get(*ht, scheme_make_integer(vector_length));
	      else
		ph = NULL;

	      if (!ph) {
		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				"read: no #%ld= preceding #%ld#",
				vector_length, vector_length);
		return scheme_void;
	      }
	      return ph;
	    }
	    if (ch == '=' && (vector_length != -1)) {
	      /* Not a vector after all: a graph definition */
	      Scheme_Object *v, *ph;
              intptr_t in_pos;

	      if (stxsrc)
		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				"read: #..= expressions not allowed in read-syntax mode");

	      if (!params->can_read_graph)
		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				 "read: #..= expressions" NOT_ENABLED_str);

	      if (digits > MAX_GRAPH_ID_DIGITS)
		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				 "read: graph id too long in #%s=",
				 tagbuf);

	      if (*ht) {
		if (scheme_hash_get(*ht, scheme_make_integer(vector_length))) {
		  scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				  "read: multiple #%ld= tags",
				  vector_length);
		  return NULL;
		}
	      } else {
		Scheme_Hash_Table *tht;
		tht = scheme_make_hash_table(SCHEME_hash_ptr);
		*ht = tht;
	      }
	      ph = scheme_alloc_small_object();
	      ph->type = scheme_placeholder_type;

	      scheme_hash_set(*ht, scheme_make_integer(vector_length), (void *)ph);

              scheme_tell_all(port, NULL, NULL, &in_pos);

	      v = read_inner(port, stxsrc, ht, indentation, params, 0);
	      if (SCHEME_EOFP(v))
		scheme_read_err(port, stxsrc, line, col, pos, MINSPAN(port, pos, in_pos-pos), EOF, indentation,
				"read: expected an element for graph (found end-of-file)");
	      SCHEME_PTR_VAL(ph) = v;

	      return v;
	    }

	    {
	      char *lbuffer;
	      int pch = ch, ulen, blen;

	      if ((pch == EOF) || (pch == SCHEME_SPECIAL))
		pch = 0;

	      ulen = scheme_char_strlen(tagbuf);
	      blen = scheme_utf8_encode_all(tagbuf, ulen, NULL);
	      lbuffer = (char *)scheme_malloc_atomic(blen + MAX_UTF8_CHAR_BYTES + 1);
	      scheme_utf8_encode_all(tagbuf, ulen, (unsigned char *)lbuffer);
	      blen += scheme_utf8_encode((mzchar *)&pch, 0, 1,
					 (unsigned char *)lbuffer, blen,
					 0);
	      lbuffer[blen] = 0;

	      scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation,
			      "read: bad syntax `#%s'",
			      lbuffer);

	      return NULL;
	    }
	  }
	  break;
	}
      if (!special_value) {
	/* We get here only in honu mode */
	scheme_read_err(port, stxsrc, line, col, pos, 2, ch, indentation,
			"read: bad syntax `#%c'",
			ch);
	return NULL;
      }
      break;
    case '/':
      if (params->honu_mode) {
	int ch2;
	ch2 = scheme_peekc_special_ok(port);
	if ((ch2 == '/') || (ch2 == '*')) {
	  /* Comment */
	  scheme_ungetc('/', port);
	  ch = skip_whitespace_comments(port, stxsrc, ht, indentation, params);
	  goto start_over_with_ch;
	}
      }
      special_value = read_symbol(ch, 0, port, stxsrc, line, col, pos, ht, indentation, params, table);
      break;
    case '>':
    case '<':
      if ((params->honu_mode) && (comment_mode & RETURN_HONU_ANGLE)) {
        Scheme_Object *v;
        v = read_symbol(ch, 0, port, stxsrc, line, col, pos, ht, indentation, params, table);
        special_value = v;
        if (SCHEME_STXP(v))
          v = SCHEME_STX_VAL(v);
        if (SCHEME_SYMBOLP(v) && (SCHEME_SYM_LEN(v) == 1)
            && ((SCHEME_SYM_VAL(v)[0] == '>') || (SCHEME_SYM_VAL(v)[0] == '<'))) {
          if (SCHEME_SYM_VAL(v)[0] == '<')
            v = honu_angle_open;
          else
            v = honu_angle_close;
          if (SCHEME_STXP(special_value))
            special_value = scheme_datum_to_syntax(v, scheme_false, special_value, 0, 1);
          else
            special_value = v;
        }
      } else
        special_value = read_symbol(ch, 0, port, stxsrc, line, col, pos, ht, indentation, params, table);
      break;
    default:
      if (isdigit_ascii(ch))
	special_value = read_number(ch, port, stxsrc, line, col, pos, 0, 0, 10, 0, ht, indentation, params, table);
      else
	special_value = read_symbol(ch, 0, port, stxsrc, line, col, pos, ht, indentation, params, table);
      break;
    }

  /* We get here after reading a "symbol". Check for a comment. */
  {
    Scheme_Object *v = special_value;

    if (scheme_special_comment_value(v)) {
      /* a "comment" */
      if (comment_mode & RETURN_FOR_SPECIAL_COMMENT)
	return NULL;
      else {
	special_value_need_copy = 0;
	goto start_over;
      }
    } else if (SCHEME_STXP(v)) {
      if (!stxsrc)
	v = scheme_syntax_to_datum(v, 0, NULL);
    } else if (stxsrc) {
      Scheme_Object *s;
      s = scheme_make_stx_w_offset(scheme_false, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
      v = scheme_datum_to_syntax(v, s, scheme_false, 1, 0);
    }
    if (special_value_need_copy && !stxsrc) {
      set_need_copy(ht);
    }
    return v;
  }
}

static Scheme_Object *
read_inner(Scheme_Object *port, Scheme_Object *stxsrc, Scheme_Hash_Table **ht,
	   Scheme_Object *indentation, ReadParams *params,
	   int comment_mode)
{
  return read_inner_inner(port, stxsrc, ht, indentation, params, comment_mode, -1, params->table, 0);
}

#ifdef DO_STACK_CHECK
static Scheme_Object *resolve_references(Scheme_Object *obj,
					 Scheme_Object *port,
					 Scheme_Object *top,
                                         Scheme_Hash_Table *dht,
                                         Scheme_Hash_Table *tht,
                                         int clone,
                                         int tail_depth);

static Scheme_Object *resolve_k(void)
{
  Scheme_Thread *p = scheme_current_thread;
  Scheme_Object *o = (Scheme_Object *)p->ku.k.p1;
  Scheme_Object *port = (Scheme_Object *)p->ku.k.p2;
  Scheme_Object *top = (Scheme_Object *)p->ku.k.p5;
  Scheme_Hash_Table *dht = (Scheme_Hash_Table *)p->ku.k.p3;
  Scheme_Hash_Table *tht = (Scheme_Hash_Table *)p->ku.k.p4;

  p->ku.k.p1 = NULL;
  p->ku.k.p2 = NULL;
  p->ku.k.p3 = NULL;
  p->ku.k.p4 = NULL;
  p->ku.k.p5 = NULL;

  return resolve_references(o, port, top, dht, tht, p->ku.k.i1, p->ku.k.i2);
}
#endif

static Scheme_Object *resolve_references(Scheme_Object *obj,
					 Scheme_Object *port,
					 Scheme_Object *top,
					 Scheme_Hash_Table *dht,
					 Scheme_Hash_Table *tht,
                                         int clone,
                                         int tail_depth)
{
  Scheme_Object *result;

#ifdef DO_STACK_CHECK
  {
# include "mzstkchk.h"
    {
      Scheme_Thread *p = scheme_current_thread;
      p->ku.k.p1 = (void *)obj;
      p->ku.k.p2 = (void *)port;
      p->ku.k.p5 = (void *)top;
      p->ku.k.p3 = (void *)dht;
      p->ku.k.p4 = (void *)tht;
      p->ku.k.i1 = clone;
      p->ku.k.i2 = tail_depth;
      return scheme_handle_stack_overflow(resolve_k);
    }
  }
#endif

  SCHEME_USE_FUEL(1);

  if (SAME_TYPE(SCHEME_TYPE(obj), scheme_placeholder_type)) {
    Scheme_Object *start = obj;
    while (SAME_TYPE(SCHEME_TYPE(obj), scheme_placeholder_type)) {
      obj = (Scheme_Object *)SCHEME_PTR_VAL(obj);
      if (SAME_OBJ(start, obj)) {
        if (port)
          scheme_read_err(port, NULL, -1, -1, -1, -1, 0, NULL,
                          "read: illegal placeholder cycle");
        else {
          scheme_arg_mismatch("make-reader-graph",
                              "illegal placeholder cycle in value: ",
                              top);
        }
        return NULL;
      }
    }
  }

  result = scheme_hash_get(dht, obj);
  if (result) {
    if (SCHEME_PAIRP(result)) {
      obj = scheme_hash_get(tht, result);
      if (obj && (SCHEME_INT_VAL(obj) == tail_depth))
        SCHEME_PAIR_FLAGS(result) |= PAIR_IS_NON_LIST;
    }
    return result;
  }

  result = obj;

  if (SCHEME_PAIRP(obj)) {
    Scheme_Object *rr;

    if (clone)
      result = scheme_make_pair(scheme_false, scheme_false);
    scheme_hash_set(dht, obj, result);

    rr = resolve_references(SCHEME_CAR(obj), port, top, dht, tht, clone, tail_depth + 1);
    SCHEME_CAR(result) = rr;

    scheme_hash_set(tht, result, scheme_make_integer(tail_depth));

    rr = resolve_references(SCHEME_CDR(obj), port, top, dht, tht, clone, tail_depth);
    SCHEME_CDR(result) = rr;

    scheme_hash_set(tht, result, NULL);

    if (clone
        && SAME_OBJ(SCHEME_CAR(obj), SCHEME_CAR(result))
        && SAME_OBJ(SCHEME_CDR(obj), SCHEME_CDR(result))) {
      /* No changes, so we don't actually have to clone. */
      result = obj;
      scheme_hash_set(dht, obj, result);
    }
  } else if (SCHEME_BOXP(obj)) {
    Scheme_Object *rr;

    if (clone) {
      result = scheme_box(scheme_false);
      if (SCHEME_IMMUTABLEP(obj))
        SCHEME_SET_IMMUTABLE(result);
    }
    scheme_hash_set(dht, obj, result);

    rr = resolve_references(SCHEME_BOX_VAL(obj), port, top, dht, tht, clone, tail_depth + 1);
    SCHEME_BOX_VAL(result) = rr;

    if (clone
        && SAME_OBJ(SCHEME_PTR_VAL(obj), SCHEME_PTR_VAL(result))) {
      result = obj;
      scheme_hash_set(dht, obj, result);
    }
  } else if (SCHEME_VECTORP(obj)
             || (clone && SCHEME_CHAPERONE_VECTORP(obj))) {
    int i, len, diff = 0;
    Scheme_Object *prev_rr, *prev_v;

    if (SCHEME_NP_CHAPERONEP(obj))
      obj = scheme_chaperone_vector_copy(obj);

    len = SCHEME_VEC_SIZE(obj);

    if (clone) {
      result = scheme_make_vector(len, scheme_false);
      if (SCHEME_IMMUTABLEP(obj))
        SCHEME_SET_IMMUTABLE(result);
    }
    scheme_hash_set(dht, obj, result);

    prev_v = prev_rr = NULL;
    for (i = 0; i < len; i++) {
      Scheme_Object *rr;
      if (SCHEME_VEC_ELS(obj)[i] == prev_v) {
	rr = prev_rr;
      } else {
	prev_v = SCHEME_VEC_ELS(obj)[i];
	rr = resolve_references(prev_v, port, top, dht, tht, clone, tail_depth + 1);
        if (!SAME_OBJ(prev_v, rr))
          diff = 1;
	prev_rr = rr;
      }
      SCHEME_VEC_ELS(result)[i] = rr;
    }

    if (clone && !diff) {
      result = obj;
      scheme_hash_set(dht, obj, result);
    }
  } else if (SAME_TYPE(SCHEME_TYPE(obj), scheme_table_placeholder_type)
             || SCHEME_HASHTRP(obj)
             || (clone && SCHEME_NP_CHAPERONEP(obj) 
                 && (SCHEME_HASHTP(SCHEME_CHAPERONE_VAL(obj))
                     || SCHEME_HASHTRP(SCHEME_CHAPERONE_VAL(obj))))) {
    Scheme_Hash_Tree *t, *base;
    Scheme_Object *a, *key, *val, *lst;
    int kind;

    if (SCHEME_NP_CHAPERONEP(obj))
      obj = scheme_chaperone_hash_table_copy(obj);

    if (SCHEME_HASHTRP(obj)) {
      int i;
      if (scheme_is_hash_tree_equal(obj))
        kind = 1;
      else if (scheme_is_hash_tree_eqv(obj))
        kind = 2;
      else
        kind = 0;
      t = (Scheme_Hash_Tree *)obj;
      lst = scheme_null;
      for (i = t->count; i--; ) {
        scheme_hash_tree_index(t, i, &key, &val);
        lst = scheme_make_pair(scheme_make_pair(key, val), lst);
      }
    } else {
      kind = SCHEME_PINT_VAL(obj);
      lst = SCHEME_IPTR_VAL(obj);
    }

    /* Create `t' to be overwritten, and create `base' to extend. */
    t = scheme_make_hash_tree(kind);
    base = scheme_make_hash_tree(kind);

    result = (Scheme_Object *)t;
    scheme_hash_set(dht, obj, result);

    lst = resolve_references(lst, port, top, dht, tht, clone, tail_depth + 1);

    for (; SCHEME_PAIRP(lst); lst = SCHEME_CDR(lst)) {
      a = SCHEME_CAR(lst);
      key = SCHEME_CAR(a);
      val = SCHEME_CDR(a);
     
      base = scheme_hash_tree_set(base, key, val);
    }
    
    t->count = base->count;
    t->root = base->root;
    t->elems_box = base->elems_box;
  } else if (SCHEME_HASHTP(obj)) {
    int i;
    Scheme_Object *key, *val, *l = scheme_null, *orig_l;
    Scheme_Hash_Table *t = (Scheme_Hash_Table *)obj, *t2;

    t2 = scheme_clone_hash_table(t);
    scheme_reset_hash_table(t2, NULL);
    result = (Scheme_Object *)t2;

    scheme_hash_set(dht, obj, (Scheme_Object *)t2);
    
    for (i = t->size; i--; ) {
      if (t->vals[i]) {
        key = t->keys[i];
        val = t->vals[i];
        l = scheme_make_pair(scheme_make_pair(key, val), l);
      }
    }

    orig_l = l;
    l = resolve_references(l, port, top, dht, tht, clone, tail_depth + 1);

    if (SAME_OBJ(l, orig_l)) {
      result = obj;
      scheme_hash_set(dht, obj, result);
    } else {
      for (; SCHEME_PAIRP(l); l = SCHEME_CDR(l)) {
        val = SCHEME_CAR(l);
        key = SCHEME_CAR(val);
        val = SCHEME_CDR(val);
        
        scheme_hash_set(t2, key, val);
      }
    }
  } else if (SCHEME_STRUCTP(obj)
             || (clone && SCHEME_CHAPERONE_STRUCTP(obj))) {
    Scheme_Structure *s;
    if (clone && SCHEME_CHAPERONEP(obj))
      s = (Scheme_Structure *)SCHEME_CHAPERONE_VAL(obj);
    else
      s = (Scheme_Structure *)obj;
    if (s->stype->prefab_key) {
      /* prefab */
      int c, i, diff;
      Scheme_Object *prev_v, *v;

      if (clone) {
        result = scheme_clone_prefab_struct_instance((Scheme_Structure *)obj);
      }
      scheme_hash_set(dht, obj, result);

      c = s->stype->num_slots;
      diff = 0;
      for (i = 0; i < c; i++) {
        prev_v = ((Scheme_Structure *)result)->slots[i];
	v = resolve_references(prev_v, port, top, dht, tht, clone, tail_depth + 1);
        if (!SAME_OBJ(prev_v, v))
          diff = 1;
        ((Scheme_Structure *)result)->slots[i] = v;
      }

      if (clone && !diff) {
        result = obj;
        scheme_hash_set(dht, obj, result);
      }
    }
  }

  return result;
}

static Scheme_Object *
_internal_read(Scheme_Object *port, Scheme_Object *stxsrc, int crc, int cant_fail, int honu_mode, 
               int recur, int expose_comment, int extra_char, Scheme_Object *init_readtable,
               Scheme_Object *magic_sym, Scheme_Object *magic_val,
               Scheme_Object *delay_load_info, int get_info)
{
  Scheme_Object *v, *v2;
  Scheme_Config *config;
  Scheme_Hash_Table **ht = NULL;
  ReadParams params;

  config = scheme_current_config();

  if (get_info) {
    params.table = NULL;
  } else {
    v = scheme_get_param(config, MZCONFIG_READTABLE);
    if (SCHEME_TRUEP(v))
      params.table = (Readtable *)v;
    else
      params.table = NULL;
  }
  params.can_read_compiled = crc;
  v = scheme_get_param(config, MZCONFIG_CAN_READ_PIPE_QUOTE);
  params.can_read_pipe_quote = SCHEME_TRUEP(v);
  v = scheme_get_param(config, MZCONFIG_CAN_READ_BOX);
  params.can_read_box = SCHEME_TRUEP(v);
  v = scheme_get_param(config, MZCONFIG_CAN_READ_GRAPH);
  params.can_read_graph = SCHEME_TRUEP(v);
  if (crc || get_info) {
    params.can_read_reader = 1;
    params.can_read_lang = 1;
  } else {
    v = scheme_get_param(config, MZCONFIG_CAN_READ_READER);
    params.can_read_reader = SCHEME_TRUEP(v);
    v = scheme_get_param(config, MZCONFIG_CAN_READ_LANG);
    params.can_read_lang = SCHEME_TRUEP(v);
  }
  v = scheme_get_param(config, MZCONFIG_CASE_SENS);
  params.case_sensitive = SCHEME_TRUEP(v);
  v = scheme_get_param(config, MZCONFIG_SQUARE_BRACKETS_ARE_PARENS);
  params.square_brackets_are_parens = SCHEME_TRUEP(v);
  v = scheme_get_param(config, MZCONFIG_CURLY_BRACES_ARE_PARENS);
  params.curly_braces_are_parens = SCHEME_TRUEP(v);
  v = scheme_get_param(config, MZCONFIG_READ_DECIMAL_INEXACT);
  params.read_decimal_inexact = SCHEME_TRUEP(v);
  v = scheme_get_param(config, MZCONFIG_CAN_READ_QUASI);
  params.can_read_quasi = SCHEME_TRUEP(v);
  v = scheme_get_param(config, MZCONFIG_CAN_READ_DOT);
  params.can_read_dot = SCHEME_TRUEP(v);
  v = scheme_get_param(config, MZCONFIG_CAN_READ_INFIX_DOT);
  params.can_read_infix_dot = SCHEME_TRUEP(v);
  params.read_relative_path = NULL;
  if (!delay_load_info)
    delay_load_info = scheme_get_param(config, MZCONFIG_DELAY_LOAD_INFO);
  if (SCHEME_TRUEP(delay_load_info))
    params.delay_load_info = delay_load_info;
  else
    params.delay_load_info = NULL;
  params.honu_mode = honu_mode;
  if (honu_mode)
    params.table = NULL;
  params.skip_zo_vers_check = cant_fail;
  params.magic_sym = magic_sym;
  params.magic_val = magic_val;

  ht = NULL;
  if (recur) {
    /* Check whether this is really a recursive call. If so,
       we get a pointer to a hash table for cycles: */
    v = scheme_extract_one_cc_mark(NULL, unresolved_uninterned_symbol);
    if (v && SCHEME_RPAIRP(v)) {
      if (SCHEME_FALSEP(SCHEME_CDR(v)) == !stxsrc)
	ht = (Scheme_Hash_Table **)SCHEME_CAR(v);
    }
  }
  if (!ht) {
    ht = MALLOC_N(Scheme_Hash_Table *, 1);
    recur = 0;
  }

  do {
    v = read_inner_inner(port, stxsrc, ht, scheme_null, &params, 
			 (RETURN_FOR_HASH_COMMENT 
			  | (expose_comment ? (RETURN_FOR_COMMENT | RETURN_FOR_SPECIAL_COMMENT) : 0)),
			 extra_char, 
			 (init_readtable 
			  ? (SCHEME_FALSEP(init_readtable)
			     ? NULL
			     : (Readtable *)init_readtable)
			  : params.table),
                         get_info);

    extra_char = -1;

    if (*ht && !recur) {
      /* Resolve placeholders: */
      int clone = 0;
      Scheme_Hash_Table *dht, *tht;

      if (stxsrc)
        scheme_signal_error("internal error: read-syntax has graph references");

      /* If we ever called an external reader, 
         then we need to clone everything. */
      if (scheme_hash_get(*ht, tainted_uninterned_symbol))
        clone = 1;

      dht = scheme_make_hash_table(SCHEME_hash_ptr);
      tht = scheme_make_hash_table(SCHEME_hash_ptr);

      if (v)
	v = resolve_references(v, port, NULL, dht, tht, clone, 0);

      /* In case some placeholders were introduced by #;: */
      v2 = scheme_hash_get(*ht, unresolved_uninterned_symbol);
      if (v2)
	resolve_references(v2, port, NULL, dht, tht, clone, 0);

      if (!v)
	*ht = NULL;
    }

    if (!v && expose_comment) {
      /* Return to indicate comment: */
      v = scheme_alloc_small_object();
      v->type = scheme_special_comment_type;
      SCHEME_PTR_VAL(v) = scheme_false;
      return v;
    }
  } while (!v);

  return v;
}

static void *scheme_internal_read_k(void)
{
  Scheme_Thread *p = scheme_current_thread;
  Scheme_Object *port = (Scheme_Object *)p->ku.k.p1;
  Scheme_Object *stxsrc = (Scheme_Object *)p->ku.k.p2;
  Scheme_Object *init_readtable = (Scheme_Object *)p->ku.k.p3;
  Scheme_Object *magic_sym = (Scheme_Object *)p->ku.k.p4;
  Scheme_Object *magic_val = NULL;
  Scheme_Object *delay_load_info = (Scheme_Object *)p->ku.k.p5;

  p->ku.k.p1 = NULL;
  p->ku.k.p2 = NULL;
  p->ku.k.p3 = NULL;
  p->ku.k.p4 = NULL;
  p->ku.k.p5 = NULL;

  if (magic_sym) {
    magic_val = SCHEME_CDR(magic_sym);
    magic_sym = SCHEME_CAR(magic_sym);
  }

  return (void *)_internal_read(port, stxsrc, p->ku.k.i1, 0, p->ku.k.i2, 
                                p->ku.k.i3 & 0x2, p->ku.k.i3 & 0x1, 
                                p->ku.k.i4, init_readtable,
                                magic_sym, magic_val, delay_load_info, 0);
}

Scheme_Object *
scheme_internal_read(Scheme_Object *port, Scheme_Object *stxsrc, int crc, int cantfail, int honu_mode, 
		     int recur, int expose_comment, int pre_char, Scheme_Object *init_readtable, 
		     Scheme_Object *magic_sym, Scheme_Object *magic_val,
                     Scheme_Object *delay_load_info)
{
  Scheme_Thread *p = scheme_current_thread;

  if (crc < 0)
    crc = SCHEME_TRUEP(scheme_get_param(scheme_current_config(), MZCONFIG_CAN_READ_COMPILED));

  if (cantfail) {
    return _internal_read(port, stxsrc, crc, cantfail, honu_mode, recur, expose_comment, -1, NULL, 
                          magic_sym, magic_val, delay_load_info, 0);
  } else {
    if (magic_sym)
      magic_sym = scheme_make_pair(magic_sym, magic_val);

    p->ku.k.p1 = (void *)port;
    p->ku.k.p2 = (void *)stxsrc;
    p->ku.k.i1 = crc;
    p->ku.k.i2 = honu_mode;
    p->ku.k.i3 = ((recur ? 0x2 : 0) | (expose_comment ? 0x1 : 0));
    p->ku.k.i4 = pre_char;
    p->ku.k.p3 = (void *)init_readtable;
    p->ku.k.p4 = (void *)magic_sym;
    p->ku.k.p5 = (void *)delay_load_info;

    return (Scheme_Object *)scheme_top_level_do(scheme_internal_read_k, 0);
  }
}

Scheme_Object *scheme_read(Scheme_Object *port)
{
  return scheme_internal_read(port, NULL, -1, 0, 0, 0, 0, -1, NULL, NULL, NULL, 0);
}

Scheme_Object *scheme_read_syntax(Scheme_Object *port, Scheme_Object *stxsrc)
{
  return scheme_internal_read(port, stxsrc, -1, 0, 0, 0, 0, -1, NULL, NULL, NULL, 0);
}

Scheme_Object *scheme_resolve_placeholders(Scheme_Object *obj)
{
  return resolve_references(obj, NULL, obj, 
                            scheme_make_hash_table(SCHEME_hash_ptr),
                            scheme_make_hash_table(SCHEME_hash_ptr),
                            1, 0);
}

/*========================================================================*/
/*                             list reader                                */
/*========================================================================*/

static Scheme_Object *attach_shape_property(Scheme_Object *list, 
					    Scheme_Object *stxsrc, 
					    ReadParams *params, 
					    int closer);

static int next_is_delim(Scheme_Object *port,
			 ReadParams *params,
			 int brackets,
			 int braces)
{
  int next;
  next = scheme_peekc_special_ok(port);
  return ((next == EOF)
	  || (next == SCHEME_SPECIAL)
	  || (!params->table 
	      && (scheme_isspace(next)
		  || (next == '(')
		  || (next == ')')
		  || (next == '"')
		  || (next == ';')
		  || (next == '\'')
		  || (next == '`')
		  || (next == ',')
		  || ((next == '[') && brackets)
		  || ((next == '{') && braces)
		  || ((next == ']') && brackets)
		  || ((next == '}') && braces)))
	  || (params->table 
	      && (readtable_kind(params->table, next, params) 
		  & (READTABLE_WHITESPACE | READTABLE_TERMINATING))));
}

static const char *mapping_name(ReadParams *params, int ch, const char *def, int name_pos)
{
  if (params->table) {
    int i;
    char *buf = "";
    Scheme_Object *v;
    Scheme_Hash_Table *mapping;

    if (params->table->names) {
      if (params->table->names[name_pos])
        return params->table->names[name_pos];
    }

    mapping = params->table->mapping;
    if (!scheme_hash_get(mapping, scheme_make_integer(ch))) {
      buf = (char *)scheme_malloc_atomic(4);
      sprintf(buf, "`%c'", ch);
    }

    for (i = mapping->size; i--; ) {
      if (mapping->vals[i]) {
        v = mapping->vals[i];
        if ((SCHEME_INT_VAL(SCHEME_CAR(v)) == READTABLE_MAPPED)
            && (SCHEME_INT_VAL(SCHEME_CDR(v)) == ch)) {
          int len;
          mzchar a[2];
          char *naya, utf8_buf[MAX_UTF8_CHAR_BYTES + 1];

          v = mapping->keys[i];
          a[0] = (mzchar)SCHEME_INT_VAL(v);
          len = scheme_utf8_encode_all(a, 1, (unsigned char *)utf8_buf);
          utf8_buf[len] = 0;

          naya = (char *)scheme_malloc_atomic(len + 5 + strlen(buf));
          sprintf(naya, "`%s'", utf8_buf);
          if (*buf) {
            sprintf(naya XFORM_OK_PLUS len + 2, " or %s", buf);
          }
          buf = naya;
        }
      }
    }

    if (!params->table->names) {
      char **a;
      a = MALLOC_N(char*, 7);
      params->table->names = a;
    }
    params->table->names[name_pos] = buf;

    return buf;
  } else
    return def;
}

static const char *closer_name(ReadParams *params, int closer)
{
  int pos;
  const char *def;

  switch (closer) {
  case ')':
    pos = 0;
    def = "`)'";
    break;
  case ']':
    pos = 1;
    def = "`]'";
    break;
  case '}':
  default:
    pos = 2;
    def = "`}'";
    break;
  }

  return mapping_name(params, closer, def, pos);
}

static const char *opener_name(ReadParams *params, int opener)
{
  int pos;
  const char *def;

  switch (opener) {
  case '(':
    pos = 3;
    def = "`('";
    break;
  case '[':
    pos = 4;
    def = "`['";
    break;
  case '{':
  default:
    pos = 5;
    def = "`{'";
    break;
  }

  return mapping_name(params, opener, def, pos);
}

static const char *dot_name(ReadParams *params)
{
  return mapping_name(params, '.', "`.'", 6);
}

static Scheme_Object *combine_angle_brackets(Scheme_Object *list);

/* "(" (or other opener) has already been read */
static Scheme_Object *
read_list(Scheme_Object *port,
	  Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
	  int opener, int closer, int shape, int use_stack,
	  Scheme_Hash_Table **ht,
	  Scheme_Object *indentation,
	  ReadParams *params)
{
  Scheme_Object *list = NULL, *last = NULL, *car, *cdr, *pair, *infixed = NULL, *prefetched = NULL;
  int ch = 0, got_ch_already = 0, effective_ch;
  int brackets = params->square_brackets_are_parens;
  int braces = params->curly_braces_are_parens;
  intptr_t start, startcol, startline, dotpos, dotcol, dotline, dot2pos, dot2line, dot2col, init_span;

  scheme_tell_all(port, &startline, &startcol, &start);
  init_span = 1;

  if (stxsrc) {
    /* Push onto the indentation stack: */
    Scheme_Indent *indt;
    indt = (Scheme_Indent *)scheme_malloc_atomic_tagged(sizeof(Scheme_Indent));
    indt->type = scheme_indent_type;

    indt->closer = closer;
    indt->max_indent = startcol + 1;
    indt->multiline = 0;
    indt->suspicious_line = 0;
    indt->suspicious_quote = 0;
    indt->start_line = startline;
    indt->last_line = startline;

    indentation = scheme_make_pair((Scheme_Object *)indt, indentation);
  }

  while (1) {
    if (prefetched)
      ch = 0;
    else if (got_ch_already)
      got_ch_already = 0;
    else
      ch = skip_whitespace_comments(port, stxsrc, ht, indentation, params);

    if ((ch == EOF) && (closer != EOF)) {
      char *suggestion = "";
      if (SCHEME_PAIRP(indentation)) {
	Scheme_Indent *indt;

	indt = (Scheme_Indent *)SCHEME_CAR(indentation);
	if (indt->suspicious_line) {
	  suggestion = scheme_malloc_atomic(100);
	  sprintf(suggestion,
		  "; indentation suggests a missing %s before line %" PRIdPTR,
		  closer_name(params, indt->suspicious_closer),
		  indt->suspicious_line);
	}
      }

      scheme_read_err(port, stxsrc, startline, startcol, start, MINSPAN(port, start, init_span), EOF, indentation,
		      "read: expected a %s to close `%c'%s", 
                      closer_name(params, closer), 
                      opener,
                      suggestion);
      return NULL;
    }

    effective_ch = readtable_effective_char(params->table, ch);

    if (effective_ch == closer) {
      if (shape == mz_shape_hash_elem) {
	scheme_read_err(port, stxsrc, startline, startcol, start, SPAN(port, start), ch, indentation,
			"read: expected hash pair (with key and value separated by %s) before `%c'",
                        dot_name(params),
			ch);
	return NULL;
      }

      if (params->honu_mode) {
	/* Finish up the list */
	if (!list)
	  list = scheme_null;
	if (closer == ')')
	  car = honu_parens;
	else if (closer == ']')
	  car = honu_brackets;
	else if (closer == '}')
	  car = honu_braces;
	else
	  car = NULL;
	if (car) {
	  if (stxsrc)
	    car = scheme_make_stx_w_offset(car, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
	  list = scheme_make_pair(car, list);
	}
      } else {
	if (!list) {
	  list = scheme_null;
	}
      }
      pop_indentation(indentation);
      list = combine_angle_brackets(list);
      list = (stxsrc
	      ? scheme_make_stx_w_offset(list, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG)
	      : list);
      list = attach_shape_property(list, stxsrc, params, closer);
      return list;
    }

    if (shape == mz_shape_hash_list) {
      /* Make sure we found a parenthesized something. */
      if (!(effective_ch == '(')
	  && !(effective_ch == '[' && params->square_brackets_are_parens)
	  && !(effective_ch == '{' && params->curly_braces_are_parens)) {
	intptr_t xl, xc, xp;
        const char *sbname, *cbname;
	
	/* If it's a special or we have a readtable, we need to read ahead
	   to make sure that it's not a comment. For consistency, always
	   read ahead. */
	scheme_ungetc(ch, port);
	prefetched = read_inner(port, stxsrc, ht, indentation, params, 
                                RETURN_FOR_SPECIAL_COMMENT | RETURN_HONU_ANGLE);
	if (!prefetched)
	  continue; /* It was a comment; try again. */

        sbname = (params->square_brackets_are_parens ? opener_name(params, '[') : "");
        cbname = (params->curly_braces_are_parens ? opener_name(params, '{') : "");

        scheme_tell_all(port, &xl, &xc, &xp);
	scheme_read_err(port, stxsrc, xl, xc, xp, 1,
			ch, indentation,
			"read: expected %s%s%s%s%s to start a hash pair",
                        opener_name(params, '('),
                        params->square_brackets_are_parens ? " or " : "",
                        sbname,
                        params->curly_braces_are_parens ? " or " : "",
                        cbname);
	return NULL;
      } else {
	/* Found paren. Use read_list directly so we can specify mz_shape_hash_elem. */
	intptr_t xl, xc, xp;
	scheme_tell_all(port, &xl, &xc, &xp);
	car = read_list(port, stxsrc, xl, xc, xp,
			ch, ((effective_ch == '(') ? ')' : ((effective_ch == '[') ? ']' : '}')),
			mz_shape_hash_elem, use_stack, ht, indentation, params);
	/* car is guaranteed to have an appropriate shape */
      }
    } else {
      if (prefetched) {
	car = prefetched;
	prefetched = NULL;
      } else {
	scheme_ungetc(ch, port);
	car = read_inner(port, stxsrc, ht, indentation, params, 
                         RETURN_FOR_SPECIAL_COMMENT | RETURN_HONU_ANGLE);
	if (!car) continue; /* special was a comment */
      }
      /* can't be eof, due to check above */
    }

    pair = scheme_make_pair(car, scheme_null);

  retry_before_dot:

    ch = skip_whitespace_comments(port, stxsrc, ht, indentation, params);
    effective_ch = readtable_effective_char(params->table, ch);
    if ((effective_ch == closer) && !params->honu_mode) {
      if (shape == mz_shape_hash_elem) {
	scheme_read_err(port, stxsrc, startline, startcol, start, SPAN(port, start), ch, indentation,
			"read: expected %s and value for hash before `%c'",
                        dot_name(params),
			ch);
	return NULL;
      }

      cdr = pair;
      if (!list)
	list = cdr;
      else
	SCHEME_CDR(last) = cdr;

      if (infixed) {
	/* Assert: we're not using the list stack */
	list = scheme_make_pair(infixed, list);
      }

      pop_indentation(indentation);
      if (params->honu_mode)
        list = combine_angle_brackets(list);
      list = (stxsrc
	      ? scheme_make_stx_w_offset(list, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG)
	      : list);
      list = attach_shape_property(list, stxsrc, params, closer);
      return list;
    } else if (!params->honu_mode
	       && params->can_read_dot
	       && (effective_ch == '.')
	       && next_is_delim(port, params, brackets, braces)) {
      int dot_ch = ch;

      scheme_tell_all(port, &dotline, &dotcol, &dotpos);

      track_indentation(indentation, dotline, dotcol);

      if (((shape != mz_shape_cons) 
           && (shape != mz_shape_hash_elem)
           && (shape != mz_shape_vec_plus_infix))
          || infixed) {
	scheme_read_err(port, stxsrc, dotline, dotcol, dotpos, 1, 0, indentation,
			"read: illegal use of `%c'",
                        dot_ch);
	return NULL;
      }
      /* can't be eof, due to check above: */
      cdr = read_inner(port, stxsrc, ht, indentation, params, RETURN_HONU_ANGLE);
      ch = skip_whitespace_comments(port, stxsrc, ht, indentation, params);
      effective_ch = readtable_effective_char(params->table, ch);
      if ((effective_ch != closer) || (shape == mz_shape_vec_plus_infix)) {
	if (params->can_read_infix_dot 
            && (effective_ch == '.') 
            && next_is_delim(port, params, brackets, braces)) {
	  /* Parse as infix: */

	  if (shape == mz_shape_hash_elem) {
	    scheme_read_err(port, stxsrc, startline, startcol, start, SPAN(port, start), ch, indentation,
			    "read: expected %s after hash value",
			    closer_name(params, closer));
	    return NULL;
	  }

	  {
	    scheme_tell_all(port, &dot2line, &dot2col, &dot2pos);
	    track_indentation(indentation, dot2line, dot2col);
	  }

	  infixed = cdr;

	  if (!list)
	    list = pair;
	  else
	    SCHEME_CDR(last) = pair;
	  last = pair;

	  /* Make sure there's not a closing paren immediately after the dot: */
	  ch = skip_whitespace_comments(port, stxsrc, ht, indentation, params);
          effective_ch = readtable_effective_char(params->table, ch);
	  if ((effective_ch == closer) || (ch == EOF)) {
	    scheme_read_err(port, stxsrc, dotline, dotcol, dotpos, 1, (ch == EOF) ? EOF : 0, indentation,
			    "read: illegal use of `%c'", ch);
	    return NULL;
	  }
	  got_ch_already = 1;
	} else {
	  scheme_read_err(port, stxsrc, dotline, dotcol, dotpos, 1, (ch == EOF) ? EOF : 0, indentation,
			  "read: illegal use of `%c'",
                          dot_ch);
	  return NULL;
	}
      } else {
	SCHEME_CDR(pair) = cdr;
	cdr = pair;
	if (!list)
	  list = cdr;
	else
	  SCHEME_CDR(last) = cdr;

	/* Assert: infixed is NULL (otherwise we raised an exception above) */

	pop_indentation(indentation);
        if (params->honu_mode)
          list = combine_angle_brackets(list);
	list = (stxsrc
		? scheme_make_stx_w_offset(list, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG)
		: list);
	list = attach_shape_property(list, stxsrc, params, closer);
	return list;
      }
    } else {
      if ((ch == SCHEME_SPECIAL) 
          || (params->table && (ch != EOF) && (shape != mz_shape_hash_list))) {
	/* We have to try the read, because it might be a comment. */
	scheme_ungetc(ch, port);
	prefetched = read_inner(port, stxsrc, ht, indentation, params, 
                                RETURN_FOR_SPECIAL_COMMENT | RETURN_HONU_ANGLE);
	if (!prefetched)
	  goto retry_before_dot;
      } else {
	got_ch_already = 1;
      }

      if (shape == mz_shape_hash_elem) {
	scheme_read_err(port, stxsrc, startline, startcol, start, SPAN(port, start), ch, indentation,
			"read: expected %s and value for hash",
                        dot_name(params));
	return NULL;
      }

      cdr = pair;
      if (!list)
	list = cdr;
      else
	SCHEME_CDR(last) = cdr;
      last = cdr;
    }
  }
}

static Scheme_Object *combine_angle_brackets(Scheme_Object *list)
{
  Scheme_Object *l, *a, *open_stack = NULL, *prev = NULL;
  int i, ch;

  for (l = list; !SCHEME_NULLP(l); l = SCHEME_CDR(l)) {
    a = SCHEME_CAR(l);
    if (SCHEME_STXP(a))
      a = SCHEME_STX_VAL(a);
    if (SAME_OBJ(a, honu_angle_open)) {
      open_stack = scheme_make_raw_pair(scheme_make_raw_pair(l, prev),
                                        open_stack);
      /* Tentatively assume no matching close: */
      a = scheme_intern_symbol("<");
      if (SCHEME_STXP(SCHEME_CAR(l)))
        a = scheme_datum_to_syntax(a, scheme_false, SCHEME_CAR(l), 0, 1);
      SCHEME_CAR(l) = a;
    } else if (SAME_OBJ(a, honu_angle_close)) {
      if (open_stack) {
        /* A matching close --- combine the angle brackets! */
        Scheme_Object *open, *open_prev;
        Scheme_Object *naya, *ang, *seq;
        open = SCHEME_CAR(open_stack);
        open_prev = SCHEME_CDR(open);
        open = SCHEME_CAR(open);
        open_stack = SCHEME_CDR(open_stack);
        ang = honu_angles;
        if (SCHEME_STXP(SCHEME_CAR(l))) {
          Scheme_Stx *o, *c;
          int span;
          o = (Scheme_Stx *)SCHEME_CAR(open);
          c = (Scheme_Stx *)SCHEME_CAR(l);
          if ((o->srcloc->pos >= 0) && (c->srcloc->pos >= 0))
            span = (c->srcloc->pos - o->srcloc->pos) + c->srcloc->span;
          else
            span = -1;
          ang = scheme_make_stx_w_offset(ang, 
                                         o->srcloc->line,
                                         o->srcloc->col,
                                         o->srcloc->pos,
                                         span,
                                         o->srcloc->src,
                                         STX_SRCTAG);
        }
        seq = scheme_make_pair(ang, SCHEME_CDR(open));
        SCHEME_CDR(prev) = scheme_null;
        if (SCHEME_STXP(ang)) {
          seq = scheme_datum_to_syntax(seq, scheme_false, ang, 0, 1);
        }
        naya = scheme_make_pair(seq, SCHEME_CDR(l));
        if (open_prev) {
          SCHEME_CDR(open_prev) = naya;
        } else {
          list = naya;
        }
        l = naya;
      } else {
        /* Not a matching close: */
        a = scheme_intern_symbol(">");
        if (SCHEME_STXP(SCHEME_CAR(l)))
          a = scheme_datum_to_syntax(a, scheme_false, SCHEME_CAR(l), 0, 1);
        SCHEME_CAR(l) = a;
      }
    } else if (open_stack && SCHEME_SYMBOLP(a)) {
      /* Check for ids containing -, |, or &, which have lower
         operator precedence than < and >, and which therefore break up 
         angle brackets. */
      for (i = SCHEME_SYM_LEN(a); i--; ) {
        ch = SCHEME_SYM_VAL(a)[i];
        if ((ch == '=') || (ch == '|') || (ch == '&')) {
          open_stack = NULL;
          break;
        }
      }
    }
    prev = l;
  }

  return list;
}

static Scheme_Object *attach_shape_property(Scheme_Object *list, 
					    Scheme_Object *stxsrc, 
					    ReadParams *params, 
					    int closer)
{
  if ((closer != ')') && stxsrc && !params->honu_mode) {
    Scheme_Object *opener;
    opener = ((closer == '}') 
	      ? scheme_make_ascii_character('{')
	      : scheme_make_ascii_character('['));
    return scheme_stx_property(list, paren_shape_symbol, opener);
  }
  return list;
}

/*========================================================================*/
/*                            string reader                               */
/*========================================================================*/

/* '"' has already been read */
static Scheme_Object *
read_string(int is_byte, int is_honu_char, Scheme_Object *port,
	    Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
	    Scheme_Hash_Table **ht,
	    Scheme_Object *indentation, ReadParams *params,
	    int err_ok)
{
  mzchar *buf, *oldbuf, onstack[32];
  int i, j, n, n1, ch, closer = (is_honu_char ? '\'' : '"');
  intptr_t size = 31, oldsize, in_pos, init_span;
  Scheme_Object *result;

  scheme_tell_all(port, NULL, NULL, &in_pos);
  init_span = in_pos - pos + 1;

  i = 0;
  buf = onstack;
  while ((ch = scheme_getc_special_ok(port)) != closer) {
    if ((ch == EOF) || (is_honu_char && (i > 0))) {
      if (err_ok)
	scheme_read_err(port, stxsrc, line, col, pos, MINSPAN(port, pos, init_span), ch, indentation,
			"read: expected a closing %s%s",
			is_honu_char ? "'" : "'\"'",
			(ch == EOF) ? "" : " after one character");
      return NULL;
    } else if (ch == SCHEME_SPECIAL) {
      scheme_get_ready_read_special(port, stxsrc, ht);
      if (err_ok)
	scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), SCHEME_SPECIAL, indentation,
			"read: found non-character while reading a %s",
			is_honu_char ? "character constant" : "string");
      return NULL;
    }
    /* Note: errors will tend to leave junk on the port, with an open \". */
    /* Escape-sequence handling by Eli Barzilay. */
    if (ch == '\\') {
      ch = scheme_getc_special_ok(port);
      if (ch == EOF) {
	if (err_ok)
	  scheme_read_err(port, stxsrc, line, col, pos, MINSPAN(port, pos, init_span), EOF, indentation,
			  "read: expected a closing %s",
			  is_honu_char ? "'" : "'\"'");
	return NULL;
      } else if (ch == SCHEME_SPECIAL) {
	scheme_get_ready_read_special(port, stxsrc, ht);
	if (err_ok)
	  scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), SCHEME_SPECIAL, indentation,
			  "read: found non-character while reading a %s",
			  is_honu_char ? "character constant" : "string");
	return NULL;
      }
      switch ( ch ) {
      case '\\': case '\"': case '\'': break;
      case 'a': ch = '\a'; break;
      case 'b': ch = '\b'; break;
      case 'e': ch = 27; break; /* escape */
      case 'f': ch = '\f'; break;
      case 'n': ch = '\n'; break;
      case 'r': ch = '\r'; break;
      case 't': ch = '\t'; break;
      case 'v': ch = '\v'; break;
      case '\r':
        if (scheme_peekc_special_ok(port) == '\n')
	  scheme_getc(port);
	continue; /* <---------- !!!! */
      case '\n':
        continue; /* <---------- !!!! */
      case 'x':
	ch = scheme_getc_special_ok(port);
	if (NOT_EOF_OR_SPECIAL(ch) && scheme_isxdigit(ch)) {
	  n = ch<='9' ? ch-'0' : (scheme_toupper(ch)-'A'+10);
	  ch = scheme_peekc_special_ok(port);
	  if (NOT_EOF_OR_SPECIAL(ch) && scheme_isxdigit(ch)) {
	    n = n*16 + (ch<='9' ? ch-'0' : (scheme_toupper(ch)-'A'+10));
	    scheme_getc(port); /* must be ch */
	  }
	  ch = n;
	} else {
	  if (ch == SCHEME_SPECIAL)
	    scheme_get_ready_read_special(port, stxsrc, ht);
	  if (err_ok)
	    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation,
			    "read: no hex digit following \\x in %s",
			    is_honu_char ? "character constant" : "string");
	  return NULL;
	}
	break;
      case 'u':
      case 'U':
	if (!is_byte) {
	  int maxc = ((ch == 'u') ? 4 : 8);
	  ch = scheme_getc_special_ok(port);
	  if (NOT_EOF_OR_SPECIAL(ch) && scheme_isxdigit(ch)) {
	    int count = 1;
	    n = ch<='9' ? ch-'0' : (scheme_toupper(ch)-'A'+10);
	    while (count < maxc) {
	      ch = scheme_peekc_special_ok(port);
	      if (NOT_EOF_OR_SPECIAL(ch) && scheme_isxdigit(ch)) {
		n = n*16 + (ch<='9' ? ch-'0' : (scheme_toupper(ch)-'A'+10));
		scheme_getc(port); /* must be ch */
		count++;
	      } else
		break;
	    }
	    /* disallow surrogate points, etc */
	    if (((n >= 0xD800) && (n <= 0xDFFF))
		|| (n > 0x10FFFF)) {
	      ch = -1;
	    } else {
	      ch = n;
	    }
	  } else {
	    if (ch == SCHEME_SPECIAL)
	      scheme_get_ready_read_special(port, stxsrc, ht);
	    if (err_ok)
	      scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation,
			      "read: no hex digit following \\%c in %s",
			      ((maxc == 4) ? 'u' : 'U'),
			      is_honu_char ? "character constant" : "string");
	    return NULL;
	  }
	  break;
	} /* else FALLTHROUGH!!! */
      default:
	if ((ch >= '0') && (ch <= '7')) {
	  for (n = j = 0; j < 3; j++) {
	    n1 = 8*n + ch - '0';
	    if (n1 > 255) {
	      if (err_ok)
		scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
				"read: escape sequence \\%o out of range in %s", n1,
				is_honu_char ? "character constant" : "string");
	      return NULL;
	    }
	    n = n1;
	    if (j < 2) {
	      ch = scheme_peekc_special_ok(port);
	      if (!((ch >= '0') && (ch <= '7'))) {
		break;
	      } else {
		scheme_getc(port); /* must be ch */
	      }
	    }
	  }
	  ch = n;
	} else {
	  if (err_ok)
	    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
			    "read: unknown escape sequence \\%c in %s%s", ch,
			    is_byte ? "byte " : "",
			    is_honu_char ? "character constant" : "string");
	  return NULL;
	}
	break;
      }
    } else if ((ch == '\n') || (ch == '\r')) {
      /* Suspicious string... remember the line */
      if (line > 0) {
	if (SCHEME_PAIRP(indentation)) {
	  Scheme_Indent *indt;
	  indt = (Scheme_Indent *)SCHEME_CAR(indentation);
	  /* Only remember if there's no earlier suspcious string line: */
	  if (!indt->suspicious_quote) {
	    indt->suspicious_quote = line;
	    indt->quote_for_char = is_honu_char;
	  }
	}
      }
    }

    if (ch < 0) {
      if (err_ok)
	scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
			"read: out-of-range character in %s%s",
			is_byte ? "byte " : "",
			is_honu_char ? "character constant" : "string");
      return NULL;
    }

    if (i >= size) {
      oldsize = size;
      oldbuf = buf;

      size *= 2;
      buf = (mzchar *)scheme_malloc_atomic((size + 1) * sizeof(mzchar));
      memcpy(buf, oldbuf, oldsize * sizeof(mzchar));
    }
    buf[i++] = ch;
  }
  buf[i] = '\0';

  if (is_honu_char) {
    if (i)
      result = scheme_make_character(buf[0]);
    else {
      if (err_ok)
	scheme_read_err(port, stxsrc, line, col, pos, 2, 0, indentation,
			"read: expected one character before closing '");
      return NULL;
    }
  } else if (!is_byte)
    result = scheme_make_immutable_sized_char_string(buf, i, i <= 31);
  else {
    /* buf is not UTF-8 encoded; all of the chars are less than 256.
       We just need to change to bytes.. */
    char *s;
    s = (char *)scheme_malloc_atomic(i + 1);
    for (j = 0; j < i; j++) {
      ((unsigned char *)s)[j] = buf[j];
    }
    s[i] = 0;
    result = scheme_make_immutable_sized_byte_string(s, i, 0);
  }
  if (stxsrc)
    result =  scheme_make_stx_w_offset(result, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
  return result;
}

Scheme_Object *scheme_read_byte_string(Scheme_Object *port)
/* used by GRacket */
{
  return read_string(1, 0, port,
		     NULL, 0, 0, 0,
		     NULL,
		     NULL, NULL,
		     0);
}

static Scheme_Object *
read_here_string(Scheme_Object *port, Scheme_Object *stxsrc,
		 intptr_t line, intptr_t col, intptr_t pos,
		 Scheme_Object *indentation,
		 ReadParams *params)
     /* #<< has been read already */
{
  int tlen = 0, len = 0, size = 12;
  mzchar *tag, *naya, *s, buf[12], c;
  intptr_t in_pos, init_span;
  Scheme_Object *str;

  scheme_tell_all(port, NULL, NULL, &in_pos);
  init_span = in_pos - pos + 1;

  tag = buf;
  while (1) {
    c = scheme_getc(port);
    if (c == '\n') {
      break;
    } else if (c == EOF) {
      scheme_read_err(port, stxsrc, line, col, pos, 3 + tlen, EOF, indentation,
		      "read: found end-of-file after #<< and before first and-of-line");
      return NULL;
    } else {
      if (tlen >= size) {
	size *= 2;
	naya = (mzchar *)scheme_malloc_atomic(size * sizeof(mzchar));
	memcpy(naya, tag, tlen * sizeof(mzchar));
	tag = naya;
      }
      tag[tlen++] = c;
    }
  }
  if (!tlen) {
    scheme_read_err(port, stxsrc, line, col, pos, 3, 0, indentation,
		    "read: no characters after #<< before and-of-line");
    return NULL;
  }

  size = 10 + tlen;
  s = (mzchar *)scheme_malloc_atomic(size * sizeof(mzchar));
  while (1) {
    c = scheme_getc(port);
    if (c == EOF) {
      scheme_read_err(port, stxsrc, line, col, pos, MINSPAN(port, pos, init_span), EOF, indentation,
		      "read: found end-of-file before terminating %u%s",
		      tag, 
		      (intptr_t)((tlen > 50) ? 50 : tlen),
		      (tlen > 50) ? "..." : "");
      return NULL;
    }
    if (len >= size) {
      size *= 2;
      naya = (mzchar *)scheme_malloc_atomic(size * sizeof(mzchar));
      memcpy(naya, s, len * sizeof(mzchar));
      s = naya;
    }
    s[len++] = c;
    if ((len >= tlen)
	&& ((len == tlen)
	    || (s[len - tlen - 1] == '\n'))
	&& !memcmp(s XFORM_OK_PLUS (len - tlen), tag, sizeof(mzchar) * tlen)) {
      c = scheme_peekc(port);
      if ((c == '\r') || (c == '\n') || (c == EOF))
	break;
    }
  }

  len -= (tlen + 1);
  if (len < 0)
    len = 0;

  str = scheme_make_sized_char_string(s, len, 1);

  if (stxsrc)
    str = scheme_make_stx_w_offset(str, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
  
  return str;
}

char *scheme_extract_indentation_suggestions(Scheme_Object *indentation)
{
  intptr_t suspicious_quote = 0;
  int is_honu_char = 0;
  char *suspicions = "";

  /* search back through indentation records to find the
     first suspicious quote */
  while (SCHEME_PAIRP(indentation)) {
    Scheme_Indent *indt;
    indt = (Scheme_Indent *)SCHEME_CAR(indentation);
    indentation = SCHEME_CDR(indentation);
    if (indt->suspicious_quote) {
      suspicious_quote = indt->suspicious_quote;
      is_honu_char = indt->quote_for_char;
    }
  }

  if (suspicious_quote) {
    suspicions = (char *)scheme_malloc_atomic(64);
    sprintf(suspicions,
	    "; newline within %s suggests a missing %s on line %" PRIdPTR,
	    is_honu_char ? "character" : "string",
	    is_honu_char ? "'" : "'\"'",
	    suspicious_quote);
  }

  return suspicions;
}

/*========================================================================*/
/*                            vector reader                               */
/*========================================================================*/

/* "#(" has been read */
static Scheme_Object *
read_vector (Scheme_Object *port,
	     Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
	     int opener, char closer,
	     intptr_t requestLength, const mzchar *reqBuffer,
	     Scheme_Hash_Table **ht,
	     Scheme_Object *indentation, ReadParams *params, int allow_infix)
/* requestLength == -1 => no request
   requestLength == -2 => overflow */
{
  Scheme_Object *lresult, *obj, *vec, **els;
  int len, i;

  lresult = read_list(port, stxsrc, line, col, pos, opener, closer, 
                      allow_infix ? mz_shape_vec_plus_infix : mz_shape_vec, 
                      1, ht, indentation, params);

  if (requestLength == -2) {
    scheme_raise_out_of_memory("read", "making vector of size %5", reqBuffer);
    return NULL;
  }

  if (stxsrc)
    obj = ((Scheme_Stx *)lresult)->val;
  else
    obj = lresult;

  len = scheme_list_length(obj);
  if (requestLength >= 0 && len > requestLength) {
    char buffer[20];
    sprintf(buffer, "%" PRIdPTR, requestLength);
    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
		    "read: vector length %ld is too small, "
		    "%d values provided",
		    requestLength, len);
    return NULL;
  }
  if (requestLength < 0)
    requestLength = len;
  vec = scheme_make_vector(requestLength, NULL);
  els = SCHEME_VEC_ELS(vec);
  for (i = 0; i < len ; i++) {
    els[i] = SCHEME_CAR(obj);
    obj = SCHEME_CDR(obj);
  }
  els = NULL;
  if (i < requestLength) {
    if (len)
      obj = SCHEME_VEC_ELS(vec)[len - 1];
    else {
      obj = scheme_make_integer(0);
      if (stxsrc)
	obj = scheme_make_stx_w_offset(obj, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
    }

    els = SCHEME_VEC_ELS(vec);
    for (; i < requestLength; i++) {
      els[i] = obj;
    }
    els = NULL;
  }

  if (stxsrc) {
    if (SCHEME_VEC_SIZE(vec) > 0)
      SCHEME_SET_VECTOR_IMMUTABLE(vec);
    ((Scheme_Stx *)lresult)->val = vec;
    return lresult;
  } else
    return vec;
}

/*========================================================================*/
/*                            symbol reader                               */
/*========================================================================*/

/* Also dispatches to number reader, since things not-a-number are
   symbols. */

static int check_honu_num(mzchar *buf, int i);
typedef int (*Getc_Fun_r)(Scheme_Object *port);

/* nothing has been read, except maybe some flags */
static Scheme_Object  *
read_number_or_symbol(int init_ch, int skip_rt, Scheme_Object *port,
		      Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
		      int is_float, int is_not_float,
		      int radix, int radix_set,
		      int is_symbol, int is_kw, int pipe_quote,
		      Scheme_Hash_Table **ht,
		      Scheme_Object *indentation, ReadParams *params, Readtable *table)
{
  mzchar *buf, *oldbuf, onstack[MAX_QUICK_SYMBOL_SIZE];
  int size, oldsize;
  int i, ch, quoted, quoted_ever = 0, running_quote = 0;
  int running_quote_ch = 0;
  intptr_t rq_pos = 0, rq_col = 0, rq_line = 0;
  int case_sens = params->case_sensitive;
  int decimal_inexact = params->read_decimal_inexact;
  Scheme_Object *o;
  int delim_ok;
  int ungetc_ok;
  int honu_mode, e_ok = 0;
  int far_char_ok;
  int single_escape, multiple_escape, norm_count = 0;
  Getc_Fun_r getc_special_ok_fun;

  if (!skip_rt && table) {
    /* If the readtable provides a "symbol" reader, then use it: */
    if (table->symbol_parser) {
      return readtable_call(1, init_ch, table->symbol_parser, params, 
			    port, stxsrc, line, col, pos, 0, ht, NULL);
      /* Special-comment result is handled in main loop. */
    }
  }

  ungetc_ok = scheme_peekc_is_ungetc(port);

  if (ungetc_ok) {
    getc_special_ok_fun = scheme_getc_special_ok;
  } else {
    getc_special_ok_fun = scheme_peekc_special_ok;
  }

  i = 0;
  size = MAX_QUICK_SYMBOL_SIZE - 1;
  buf = onstack;

  if (init_ch < 0)
    ch = getc_special_ok_fun(port);
  else {
    /* Assert: this one won't need to be ungotten */
    ch = init_ch;
  }

  if (is_float || is_not_float || radix_set)
    honu_mode = 0;
  else
    honu_mode = params->honu_mode;

  if (table) {
    far_char_ok = 0;
    delim_ok = 0;
  } else if (!honu_mode) {
    delim_ok = SCHEME_OK;
    far_char_ok = 1;
  } else {
    pipe_quote = 0;
    if (!is_symbol) {
      delim_ok = (HONU_NUM_OK | HONU_INUM_OK);
      e_ok = 1;
      far_char_ok = 0;
    } else if (delim[ch] & HONU_SYM_OK) {
      delim_ok = HONU_SYM_OK;
      far_char_ok = 0;
    } else {
      delim_ok = HONU_OK;
      far_char_ok = 1;
    }
  }

  while (NOT_EOF_OR_SPECIAL(ch)
	 && (running_quote
	     || (!table 
		 && !scheme_isspace(ch) 
		 && (((ch < 128) && (delim[ch] & delim_ok))
		     || ((ch >= 128) && far_char_ok)))
	     || table)) {
    if (table) {
      int v;
      v = readtable_kind(table, ch, params);
      if (!running_quote && (v & (READTABLE_TERMINATING | READTABLE_WHITESPACE)))
	break;
      single_escape = (v & READTABLE_SINGLE_ESCAPE);
      multiple_escape = (v & READTABLE_MULTIPLE_ESCAPE);
    } else {
      single_escape = (ch == '\\');
      multiple_escape = ((ch == '|') && pipe_quote);
    }
    if (!ungetc_ok) {
      if (init_ch < 0)
	scheme_getc(port); /* must be a character */
      else
	init_ch = -1;
    }
    if (single_escape && !running_quote) {
      int esc_ch = ch;
      ch = scheme_getc_special_ok(port);
      if (ch == EOF) {
	scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), EOF, indentation,
			"read: EOF following `%c' in %s", esc_ch, is_kw ? "keyword" : "symbol");
	return NULL;
      } else if (ch == SCHEME_SPECIAL) {
	scheme_get_ready_read_special(port, stxsrc, ht);
	scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), SCHEME_SPECIAL, indentation,
			"read: non-character following `%c' in %s", esc_ch, is_kw ? "keyword" : "symbol");
	return NULL;
      }
      quoted = 1;
      quoted_ever = 1;
    } else if (multiple_escape && (!running_quote || (ch == running_quote_ch))) {
      quoted_ever = 1;
      running_quote = !running_quote;
      running_quote_ch = ch;
      quoted = 0;

      scheme_tell_all(port, &rq_line, &rq_col, &rq_pos);

      ch = getc_special_ok_fun(port);
      continue; /* <-- !!! */
    } else
      quoted = 0;

    if (i >= size) {
      oldsize = size;
      oldbuf = buf;

      size *= 2;
      buf = (mzchar *)scheme_malloc_atomic((size + 1) * sizeof(mzchar));
      memcpy(buf, oldbuf, oldsize * sizeof(mzchar));
    }

    if (!case_sens && !quoted && !running_quote)
      norm_count++;
    else if (norm_count) {
      /* case-normalize the last norm_count characters */
      mzchar *s;
      int newlen;
      s = scheme_string_recase(buf, i - norm_count, norm_count, 3, 1, &newlen);
      if (s != buf) {
	if ((i + newlen - norm_count) >= size) {
	  oldsize = size;
	  oldbuf = buf;
	  
	  size *= 2;
	  if (size <= (i + newlen - norm_count))
	    size = 2 * (i + (newlen - norm_count));
	  buf = (mzchar *)scheme_malloc_atomic((size + 1) * sizeof(mzchar));
	  memcpy(buf, oldbuf, oldsize * sizeof(mzchar));
	}
	memcpy(buf + i - norm_count, s, sizeof(mzchar) * newlen);
      }
      i += (newlen - norm_count);
      norm_count = 0;
    }

    buf[i++] = ch;

    if (delim_ok & HONU_INUM_OK) {
      if ((ch == 'e') || (ch == 'E')) {
	/* Allow a +/- next */
	delim_ok = (HONU_NUM_OK | HONU_INUM_OK | HONU_INUM_SIGN_OK);
      } else
	delim_ok = (HONU_NUM_OK | HONU_INUM_OK);
    }

    ch = getc_special_ok_fun(port);
  }

  if (running_quote && (ch == SCHEME_SPECIAL)) {
    scheme_get_ready_read_special(port, stxsrc, ht);
    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), SCHEME_SPECIAL, indentation,
		    "read: non-character following `%c' in %s", running_quote_ch,
		    is_kw ? "keyword" : "symbol");
  }

  if (ungetc_ok)
    scheme_ungetc(ch, port);

  if (running_quote) {
    scheme_read_err(port, stxsrc, rq_line, rq_col, rq_pos, SPAN(port, rq_pos), EOF, indentation,
		    "read: unbalanced `%c'", running_quote_ch);
    return NULL;
  }

  if (norm_count) {
    /* case-normalize the last norm_count characters */
    mzchar *s;
    int newlen;
    s = scheme_string_recase(buf, i - norm_count, norm_count, 3, 1, &newlen);
    if (s != buf) {
      oldsize = size;
      oldbuf = buf;
      size = i + (newlen - norm_count) + 1;
      buf = (mzchar *)scheme_malloc_atomic((size + 1) * sizeof(mzchar));
      memcpy(buf, oldbuf, oldsize * sizeof(mzchar));
      memcpy(buf + i - norm_count, s, sizeof(mzchar) * newlen);
    }
    i += (newlen - norm_count);
  }

  buf[i] = '\0';

  if (!quoted_ever && (i == 1) 
      && (readtable_effective_char(params->table, buf[0]) == '.') 
      && !honu_mode) {
    intptr_t xl, xc, xp;
    scheme_tell_all(port, &xl, &xc, &xp);
    scheme_read_err(port, stxsrc, xl, xc, xp,
		    1, 0, indentation,
		    "read: illegal use of \".\"");
    return NULL;
  }

  if (!i && honu_mode) {
    /* If we end up with an empty string, then the first character
       is simply illegal */
    scheme_read_err(port, stxsrc, line, col, pos, 1, 0, indentation,
		    "read: illegal character: %c", ch);
    return NULL;
  }

  /* special case for ellipses in honu */
  if (honu_mode && !is_symbol && !scheme_ellipses(buf, i)) {
    /* Honu inexact syntax is not quite a subset of Scheme: it can end
       in an "f" or "d" to indicate the precision. We can easily check
       whether the string has the right shape, and then move the "f"
       or "d" in place of the "e" in that case. */
    int found_e;
    found_e = check_honu_num(buf, i);
    if (found_e < 0) {
      scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
		      "read: bad number: %5", buf);
      return NULL;
    }
    if (delim[buf[i - 1]] & HONU_INUM_OK) {
      /* We have a precision id to move */
      if (found_e) {
	/* Easy case: replace e: */
	buf[found_e] = buf[i - 1];
	i--;
      } else {
	/* Slightly harder: add a 0 at the end for the exponent */
	if (i >= size) {
	  oldsize = size;
	  oldbuf = buf;

	  size *= 2;
	  buf = (mzchar *)scheme_malloc_atomic((size + 1) * sizeof(mzchar));
	  memcpy(buf, oldbuf, oldsize * sizeof(mzchar));
	}
	buf[i++] = '0';
	buf[i] = 0;
      }
    }
  }

  if ((is_symbol || quoted_ever) && !is_float && !is_not_float && !radix_set)
    o = scheme_false;
  else {
    o = scheme_read_number(buf, i,
			   is_float, is_not_float, decimal_inexact,
			   radix, radix_set,
			   port, NULL, 0,
			   stxsrc, line, col, pos, SPAN(port, pos),
			   indentation);
  }

  if (SAME_OBJ(o, scheme_false)) {
    /* special case for ellipses in honu */
    if (honu_mode && !is_symbol && !scheme_ellipses(buf, i)) {
      scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
		      "read: bad number: %5", buf);
      return NULL;
    }
    if (is_kw) {
      o = scheme_intern_exact_char_keyword(buf, i);
    } else
      o = scheme_intern_exact_char_symbol(buf, i);
  }

  if (stxsrc)
    o = scheme_make_stx_w_offset(o, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);

  return o;
}

static Scheme_Object  *
read_number(int init_ch,
	    Scheme_Object *port,
	    Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
	    int is_float, int is_not_float,
	    int radix, int radix_set,
	    Scheme_Hash_Table **ht,
	    Scheme_Object *indentation, ReadParams *params, Readtable *table)
{
  return read_number_or_symbol(init_ch, init_ch < 0,
			       port, stxsrc, line, col, pos,
			       is_float, is_not_float,
			       radix, radix_set, 0, 0,
			       params->can_read_pipe_quote,
			       ht, indentation, params, table);
}

static Scheme_Object  *
read_symbol(int init_ch,
	    int skip_rt,
	    Scheme_Object *port,
	    Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
	    Scheme_Hash_Table **ht,
	    Scheme_Object *indentation, ReadParams *params, Readtable *table)
{
  return read_number_or_symbol(init_ch, skip_rt,
			       port, stxsrc, line, col, pos,
			       0, 0, 10, 0, 1, 0,
			       params->can_read_pipe_quote,
			       ht, indentation, params, table);
}

static Scheme_Object  *
read_keyword(int init_ch,
	     Scheme_Object *port,
	     Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
	     Scheme_Hash_Table **ht,
	     Scheme_Object *indentation, ReadParams *params, Readtable *table)
{
  return read_number_or_symbol(init_ch, 1,
			       port, stxsrc, line, col, pos,
			       0, 0, 10, 0, 1, 1,
			       params->can_read_pipe_quote,
			       ht, indentation, params, table);
}

static Scheme_Object  *
read_delimited_constant(int ch, const mzchar *str,
                        Scheme_Object *v,
                        Scheme_Object *port,
                        Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
                        Scheme_Object *indentation,
                        ReadParams *params, Readtable *table)
{
  int first_ch = ch;
  int scanpos = 1;

  if (ch == str[0]) { /* might be `T' instead of `t', for example */
    do {
      ch = scheme_getc_special_ok(port);
      if ((mzchar)ch == str[scanpos]) {
        scanpos++;
      } else {
        break;
      }
    } while (str[scanpos]);
  } else {
    /* need to show next character to show why it's wrong: */
    ch = scheme_getc_special_ok(port);
  }

  if (str[scanpos]
      || !next_is_delim(port, params, 1, 1)) {
    mzchar str_part[7], one_more[2];

    if (!str[scanpos]) {
      /* get non-delimiter again: */
      ch = scheme_getc_special_ok(port);
    }

    memcpy(str_part, str XFORM_OK_PLUS 1, (scanpos - 1) * sizeof(mzchar));
    str_part[scanpos - 1] = 0;
    if (NOT_EOF_OR_SPECIAL(ch)) {
      one_more[0] = ch;
      one_more[1] = 0;
    } else
      one_more[0] = 0;

    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos),
                    ch, indentation,
                    "read: bad syntax `#%c%5%u'",
                    first_ch,
                    str_part,
                    one_more, 
                    (intptr_t)(NOT_EOF_OR_SPECIAL(ch) ? 1 : 0));
    return NULL;
  }
            
  return (stxsrc
          ? scheme_make_stx_w_offset(v, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG)
          : v);
}

static int check_honu_num(mzchar *buf, int i)
{
  int j, found_e = 0, found_dot = 0;
  for (j = 0; j < i; j++) {
    if (buf[j] == '.') {
      if (found_dot) {
	j = 0;
	break; /* bad number */
      }
      found_dot = 1;
    } else if ((buf[j] == 'e') || (buf[j] == 'E')) {
      if (!j)
	break; /* bad number */
      found_e = j;
      /* Allow a sign next: */
      j++;
      if ((buf[j] == '+') || (buf[j] == '-'))
	j++;
      /* At least one digit: */
      if (!isdigit_ascii(buf[j])) {
	j = 0;
	break;
      }
      /* All digits, up to end: */
      while (isdigit_ascii(buf[j])) {
	j++;
      }
      if (!buf[j])
	break; /* good number */
      if (buf[j + 1]) {
	j = 0;
	break; /* bad number */
      }
      switch (buf[j]) {
      case 'd':
      case 'D':
      case 'f':
      case 'F':
	break; /* good number */
      default:
	j = 0;
	break; /* bad number */
      }
      break;
    } else if (delim[buf[j]] & HONU_INUM_OK) {
      if (j + 1 == i) {
	/* Fine -- ends in d/f, even though there's no e */
      } else {
	j = 0;
	break; /* bad number */
      }
    }
  }
  if (!j) {
    return -1;
  }
  return found_e;
}

/*========================================================================*/
/*                              char reader                               */
/*========================================================================*/

static int u_strcmp(mzchar *s, const char *_t)
{
  int i;
  unsigned char *t = (unsigned char *)_t;

  for (i = 0; s[i] && (scheme_tolower(s[i]) == scheme_tolower((mzchar)((unsigned char *)t)[i])); i++) {
  }
  if (s[i] || t[i])
    return 1;
  return 0;
}

static int scheme_ellipses(mzchar* buffer, int length){
    return u_strcmp(buffer, "...") == 0;
}

/* "#\" has been read */
static Scheme_Object *
read_character(Scheme_Object *port,
	       Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
	       Scheme_Hash_Table **ht,
	       Scheme_Object *indentation, ReadParams *params)
{
  int ch, next;

  ch = scheme_getc_special_ok(port);

  if (ch == SCHEME_SPECIAL) {
    scheme_get_ready_read_special(port, stxsrc, ht);
    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), SCHEME_SPECIAL, indentation,
		    "read: found non-character after #\\");
    return NULL;
  }

  next = scheme_peekc_special_ok(port);

  if ((ch >= '0' && ch <= '7') && (next >= '0' && next <= '7')) {
    /* a is the same as next */
    int last;

    last = (scheme_getc(port) /* is char */, scheme_peekc_special_ok(port));

    if (last != SCHEME_SPECIAL)
      scheme_getc(port); /* must be last */

    if (last < '0' || last > '7' || ch > '3') {
      scheme_read_err(port, stxsrc, line, col, pos, ((last == EOF) || (last == SCHEME_SPECIAL)) ? 3 : 4, last, indentation,
		      "read: bad character constant #\\%c%c%c",
		      ch, next, ((last == EOF) || (last == SCHEME_SPECIAL)) ? ' ' : last);
      return NULL;
    }

    ch = ((ch - '0') << 6) + ((next - '0') << 3) + (last - '0');

    return scheme_make_char(ch);
  }

  if (((ch == 'u') || (ch == 'U')) && NOT_EOF_OR_SPECIAL(next) && scheme_isxdigit(next)) {
    int count = 0, n = 0, nbuf[10], maxc = ((ch == 'u') ? 4 : 8);
    while (count < maxc) {
      ch = scheme_peekc_special_ok(port);
      if (NOT_EOF_OR_SPECIAL(ch) && scheme_isxdigit(ch)) {
	nbuf[count] = ch;
	n = n*16 + (ch<='9' ? ch-'0' : (scheme_toupper(ch)-'A'+10));
	scheme_getc(port); /* must be ch */
	count++;
      } else
	break;
    }
    /* disallow surrogate points, etc. */
    if ((n < 0)
	|| ((n >= 0xD800) && (n <= 0xDFFF))
	|| (n > 0x10FFFF)) {
      scheme_read_err(port, stxsrc, line, col, pos, count + 2, 0, indentation,
		      "read: bad character constant #\\%c%u",
		      (maxc == 4) ? 'u' : 'U',
		      nbuf, (intptr_t)count);
      return NULL;
    } else {
      ch = n;
    }
  } else if ((ch != EOF) && scheme_isalpha(ch) && NOT_EOF_OR_SPECIAL(next) && scheme_isalpha(next)) {
    mzchar *buf, *oldbuf, onstack[32];
    int i;
    intptr_t size = 31, oldsize;

    i = 1;
    buf = onstack;
    buf[0] = ch;
    while ((ch = scheme_peekc_special_ok(port), NOT_EOF_OR_SPECIAL(ch) && scheme_isalpha(ch))) {
      scheme_getc(port); /* is alpha character */
      if (i >= size) {
	oldsize = size;
	oldbuf = buf;

	size *= 2;
	buf = (mzchar *)scheme_malloc_atomic((size + 1) * sizeof(mzchar));
	memcpy(buf, oldbuf, oldsize * sizeof(mzchar));
      }
      buf[i++] = ch;
    }
    buf[i] = '\0';

    switch (scheme_tolower(buf[0])) {
    case 'n': /* maybe `newline' or 'null' or 'nul' */
      if (!u_strcmp(buf, "newline"))
	return scheme_make_char('\n');
      if (!u_strcmp(buf, "null") || !u_strcmp(buf, "nul"))
	return scheme_make_char('\0');
      break;
    case 's': /* maybe `space' */
      if (!u_strcmp(buf, "space"))
	return scheme_make_char(' ');
      break;
    case 'r': /* maybe `rubout' or `return' */
      if (!u_strcmp(buf, "rubout"))
	return scheme_make_char(0x7f);
      if (!u_strcmp(buf, "return"))
	return scheme_make_char('\r');
      break;
    case 'p': /* maybe `page' */
      if (!u_strcmp(buf, "page"))
	return scheme_make_char('\f');
      break;
    case 't': /* maybe `tab' */
      if (!u_strcmp(buf, "tab"))
	return scheme_make_char('\t');
      break;
    case 'v': /* maybe `vtab' */
      if (!u_strcmp(buf, "vtab"))
	return scheme_make_char(0xb);
      break;
    case 'b': /* maybe `backspace' */
      if (!u_strcmp(buf, "backspace"))
	return scheme_make_char('\b');
      break;
    case 'l': /* maybe `linefeed' */
      if (!u_strcmp(buf, "linefeed"))
	return scheme_make_char('\n');
      break;
    default:
      break;
    }

    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), 0, indentation,
		    "read: bad character constant: #\\%5",
		    buf);
  }

  if (ch == EOF) {
    scheme_read_err(port, stxsrc, line, col, pos, 2, EOF, indentation,
		    "read: expected a character after #\\");
  }

  return scheme_make_char(ch);
}

/*========================================================================*/
/*                            quote readers                               */
/*========================================================================*/

/* "'", etc. has been read */
static Scheme_Object *
read_quote(char *who, Scheme_Object *quote_symbol, int len,
	   Scheme_Object *port,
	   Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
	   Scheme_Hash_Table **ht,
	   Scheme_Object *indentation, ReadParams *params)
{
  Scheme_Object *obj, *ret;

  obj = read_inner(port, stxsrc, ht, indentation, params, 0);
  if (SCHEME_EOFP(obj))
    scheme_read_err(port, stxsrc, line, col, pos, len, EOF, indentation,
		    "read: expected an element for %s (found end-of-file)",
		    who);
  ret = (stxsrc
	 ? scheme_make_stx_w_offset(quote_symbol, line, col, pos, len, stxsrc, STX_SRCTAG)
	 : quote_symbol);
  ret = scheme_make_pair(ret, scheme_make_pair(obj, scheme_null));
  if (stxsrc) {
    ret = scheme_make_stx_w_offset(ret, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
  }
  return ret;
}

/* "#&" has been read */
static Scheme_Object *read_box(Scheme_Object *port,
			       Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
			       Scheme_Hash_Table **ht,
			       Scheme_Object *indentation, ReadParams *params)
{
  Scheme_Object *o, *bx;

  o = read_inner(port, stxsrc, ht, indentation, params, 0);

  if (SCHEME_EOFP(o))
    scheme_read_err(port, stxsrc, line, col, pos, 2, EOF, indentation,
		    "read: expected an element for #& box (found end-of-file)");

  bx = scheme_box(o);

  if (stxsrc) {
    SCHEME_SET_BOX_IMMUTABLE(bx);
    bx = scheme_make_stx_w_offset(bx, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
  }

  return bx;
}

/*========================================================================*/
/*                         hash table reader                              */
/*========================================================================*/

/* "(" has been read */
static Scheme_Object *read_hash(Scheme_Object *port, Scheme_Object *stxsrc,
				intptr_t line, intptr_t col, intptr_t pos,
				int opener, char closer,  int kind,
				Scheme_Hash_Table **ht,
				Scheme_Object *indentation, ReadParams *params)
{
  Scheme_Object *l;

  /* using mz_shape_hash_list ensures that l is a list of pairs */
  l = read_list(port, stxsrc, line, col, pos, opener, closer, mz_shape_hash_list, 0, ht, indentation, params);

  if (stxsrc) {
    Scheme_Object *key, *val;
    Scheme_Hash_Tree *t;

    t = scheme_make_hash_tree(kind);

    for (; SCHEME_STX_PAIRP(l); l = SCHEME_STX_CDR(l)) {
      val = SCHEME_STX_CAR(l);
      key = SCHEME_STX_CAR(val);
      key = scheme_syntax_to_datum(key, 0, NULL);
      val = SCHEME_STX_CDR(val);
      
      t = scheme_hash_tree_set(t, key, val);
    }
    
    return scheme_make_stx_w_offset((Scheme_Object *)t, line, col, pos, SPAN(port, pos), stxsrc, STX_SRCTAG);
  } else {
    /* Wait for placeholders to be resolved before mapping keys to
       values, because a placeholder may be used in a key. */
    Scheme_Object *ph;

    ph = scheme_alloc_object();
    ph->type = scheme_table_placeholder_type;
    SCHEME_IPTR_VAL(ph) = l;
    SCHEME_PINT_VAL(ph) = kind;

    if (!*ht) {
      /* So that resolve_references is called to build the table: */
      Scheme_Hash_Table *tht;
      tht = scheme_make_hash_table(SCHEME_hash_ptr);
      *ht = tht;
    }

    return ph;
  }
}

/*========================================================================*/
/*                               utilities                                */
/*========================================================================*/

static int
skip_whitespace_comments(Scheme_Object *port, Scheme_Object *stxsrc,
			 Scheme_Hash_Table **ht, Scheme_Object *indentation, ReadParams *params)
{
  int ch;
  int blockc_1, blockc_2;

  if (params->honu_mode) {
    blockc_1 = '/';
    blockc_2 = '*';
  } else {
    blockc_1 = '#';
    blockc_2 = '|';
  }

 start_over:

  if (params->table) {
    while ((ch = scheme_getc_special_ok(port), NOT_EOF_OR_SPECIAL(ch))) {
      if (!(readtable_kind(params->table, ch, params) & READTABLE_WHITESPACE))
	break;
    }
    return ch;
  } else {
    while ((ch = scheme_getc_special_ok(port), NOT_EOF_OR_SPECIAL(ch) && scheme_isspace(ch))) {}
  }

  if ((!params->honu_mode && (ch == ';'))
      || (params->honu_mode && (ch == '/')
	  && (scheme_peekc_special_ok(port) == '/'))) {
    do {
      ch = scheme_getc_special_ok(port);
      if (ch == SCHEME_SPECIAL)
	scheme_get_ready_read_special(port, stxsrc, ht);
    } while (!is_line_comment_end(ch) && ch != EOF);
    goto start_over;
  }

  if (ch == blockc_1 && (scheme_peekc_special_ok(port) == blockc_2)) {
    int depth = 0;
    int ch2 = 0;
    intptr_t col, pos, line;

    scheme_tell_all(port, &line, &col, &pos);

    (void)scheme_getc(port); /* re-read '|' */
    do {
      ch = scheme_getc_special_ok(port);

      if (ch == EOF)
	scheme_read_err(port, stxsrc, line, col, pos, MINSPAN(port, pos, 2), EOF, indentation,
			"read: end of file in #| comment");
      else if (ch == SCHEME_SPECIAL)
	scheme_get_ready_read_special(port, stxsrc, ht);

      if ((ch2 == blockc_2) && (ch == blockc_1)) {
	if (!(depth--))
	  goto start_over;
	ch = 0; /* So we don't count '#' toward an opening "#|" */
      } else if ((ch2 == blockc_1) && (ch == blockc_2)) {
	depth++;
	ch = 0; /* So we don't count '|' toward a closing "|#" */
      }
      ch2 = ch;
    } while (1);

    goto start_over;
  }
  if (ch == '#' && (scheme_peekc_special_ok(port) == ';')) {
    Scheme_Object *skipped;
    intptr_t col, pos, line;

    scheme_tell_all(port, &line, &col, &pos);

    track_indentation(indentation, line, col);

    (void)scheme_getc(port); /* re-read ';' */

    skipped = read_inner(port, stxsrc, ht, indentation, params, 0);
    if (SCHEME_EOFP(skipped))
      scheme_read_err(port, stxsrc, line, col, pos,  MINSPAN(port, pos, 2), EOF, indentation,
		      "read: expected a commented-out element for `#;' (found end-of-file)");

    /* For resolving graphs introduced in #; : */
    if (*ht) {
      Scheme_Object *v;
      v = scheme_hash_get(*ht, unresolved_uninterned_symbol);
      if (!v)
	v = scheme_null;
      v = scheme_make_pair(skipped, v);
      scheme_hash_set(*ht, unresolved_uninterned_symbol, v);
    }

    goto start_over;
  }

  return ch;
}

static void unexpected_closer(int ch,
			      Scheme_Object *port, Scheme_Object *stxsrc,
			      intptr_t line, intptr_t col, intptr_t pos,
			      Scheme_Object *indentation,
                              ReadParams *params)
{
  char *suggestion = "", *found = "unexpected";

  if (SCHEME_PAIRP(indentation)) {
    Scheme_Indent *indt;
    int opener;
    char *missing;

    indt = (Scheme_Indent *)SCHEME_CAR(indentation);

    found = scheme_malloc_atomic(100);

    if (indt->closer == '}')
      opener = '{';
    else if (indt->closer == ']')
      opener = '[';
    else
      opener = '(';

    /* Missing intermediate closers, or just need something else entirely? */
    {
      Scheme_Object *l;
      Scheme_Indent *indt2;

      missing = "expected";
      for (l = SCHEME_CDR(indentation); SCHEME_PAIRP(l); l = SCHEME_CDR(l)) {
	indt2 = (Scheme_Indent *)SCHEME_CAR(l);
	if (indt2->closer == ch) {
	  missing = "missing";
	}
      }
    }

    if (ch == indt->closer) {
      sprintf(found, "unexpected");
    } else if (indt->multiline) {
      sprintf(found,
	      "%s %s to close %s on line %" PRIdPTR ", found instead",
	      missing,
	      closer_name(params, indt->closer),
	      opener_name(params, opener),
	      indt->start_line);
    } else {
      sprintf(found,
	      "%s %s to close preceding %s, found instead",
	      missing,
	      closer_name(params, indt->closer),
	      opener_name(params, opener));
    }

    if (indt->suspicious_line) {
      suggestion = scheme_malloc_atomic(100);
      sprintf(suggestion,
	      "; indentation suggests a missing %s before line %" PRIdPTR,
	      closer_name(params, indt->suspicious_closer),
	      indt->suspicious_line);
    }
  }

  scheme_read_err(port, stxsrc, line, col, pos, 1, 0, indentation, "read: %s `%c'%s",
		  found, ch, suggestion);
}

static void pop_indentation(Scheme_Object *indentation)
{
  /* Pop off indentation stack, and propagate
     suspicions if none found earlier. */
  if (SCHEME_PAIRP(indentation)) {
    Scheme_Indent *indt;
    indt = (Scheme_Indent *)SCHEME_CAR(indentation);
    indentation = SCHEME_CDR(indentation);
    if (SCHEME_PAIRP(indentation)) {
      Scheme_Indent *old_indt;
      old_indt = (Scheme_Indent *)SCHEME_CAR(indentation);

      if (!old_indt->suspicious_line) {
	if (indt->suspicious_line) {
	  old_indt->suspicious_line = indt->suspicious_line;
	  old_indt->suspicious_closer = indt->suspicious_closer;
	}
      }
      if (!old_indt->suspicious_quote) {
	if (indt->suspicious_quote) {
	  old_indt->suspicious_quote = indt->suspicious_quote;
	  old_indt->quote_for_char = indt->quote_for_char;
	}
      }
    }
  }
}

/*========================================================================*/
/*                               .zo reader                               */
/*========================================================================*/

typedef struct Scheme_Load_Delay {
  MZTAG_IF_REQUIRED
  Scheme_Object *path;
  intptr_t file_offset, size;
  uintptr_t symtab_size;
  Scheme_Object **symtab;
  intptr_t *shared_offsets;
  Scheme_Object *relto;
  Scheme_Unmarshal_Tables *ut;
  struct CPort *current_rp;
  int perma_cache;
  unsigned char *cached;
  Scheme_Object *cached_port;
  struct Scheme_Load_Delay *clear_bytes_prev;
  struct Scheme_Load_Delay *clear_bytes_next;
} Scheme_Load_Delay;

#define ZO_CHECK(x) if (!(x)) scheme_ill_formed_code(port);
#define RANGE_CHECK(x, y) ZO_CHECK (x y)
#define RANGE_CHECK_GETS(x) RANGE_CHECK(x, <= port->size - port->pos)

typedef struct CPort {
  MZTAG_IF_REQUIRED
  uintptr_t pos, size;
  unsigned char *start;
  uintptr_t symtab_size;
  intptr_t base;
  Scheme_Object *orig_port;
  Scheme_Hash_Table **ht;
  Scheme_Unmarshal_Tables *ut;
  Scheme_Object **symtab;
  Scheme_Object *magic_sym, *magic_val;
  Scheme_Object *relto;
  intptr_t *shared_offsets;
  Scheme_Load_Delay *delay_info;
} CPort;
#define CP_GETC(cp) ((int)(cp->start[cp->pos++]))
#define CP_TELL(port) (port->pos + port->base)

static Scheme_Object *read_marshalled(int type, CPort *port);
static Scheme_Object *read_compact_list(int c, int proper, int use_stack, CPort *port);
static Scheme_Object *read_compact_quote(CPort *port, int embedded);

void scheme_ill_formed(struct CPort *port
#if TRACK_ILL_FORMED_CATCH_LINES
		       , const char *file, int line
#endif
		       )
{
  scheme_read_err(port ? port->orig_port : NULL, 
                  NULL, -1, -1, port ? CP_TELL(port) : 0, -1, 0, NULL,
		  "read (compiled): ill-formed code"
#if TRACK_ILL_FORMED_CATCH_LINES
		  " [%s:%d]", file, line
#endif
		  );
}

/* Since read_compact_number is called often, we want it to be
   a cheap call in 3m, so avoid anything that allocated --- even
   error reporting, since we can make up a valid number. */
#define NUM_ZO_CHECK(x) if (!(x)) return 0;

XFORM_NONGCING static intptr_t read_compact_number(CPort *port)
{
  intptr_t flag, v, a, b, c, d;

  NUM_ZO_CHECK(port->pos < port->size);

  flag = CP_GETC(port);

  if (flag < 128)
    return flag;
  else if (!(flag & 0x40)) {
    NUM_ZO_CHECK(port->pos < port->size);

    a = CP_GETC(port);

    v = (flag & 0x3F)
      + (a << 6);
    return v;
  } else if (!(flag & 0x20)) {
    return -(flag & 0x1F);
  }

  NUM_ZO_CHECK(port->pos + 3 < port->size);

  a = CP_GETC(port);
  b = CP_GETC(port);
  c = CP_GETC(port);
  d = CP_GETC(port);

  v = a
    + (b << 8)
    + (c << 16)
    + (d << 24);

  if (flag & 0x10)
    return v;
  else
    return -v;
}

static char *read_compact_chars(CPort *port,
				char *buffer,
				int bsize, int l)
{
  /* Range check is performed before the function is called. */
  char *s;

  if (l < bsize)
    s = buffer;
  else
    s = (char *)scheme_malloc_atomic(l + 1);

  memcpy(s, port->start + port->pos, l);
  port->pos += l;

  s[l] = 0;

  return s;
}

static Scheme_Object *read_compact_svector(CPort *port, int l)
{
  Scheme_Object *o;
  mzshort *v;

  o = scheme_alloc_object();
  o->type = scheme_svector_type;

  SCHEME_SVEC_LEN(o) = l;
  if (l > 0)
    v = MALLOC_N_ATOMIC(mzshort, l);
  else
    v = NULL;
  SCHEME_SVEC_VEC(o) = v;

  while (l--) {
    mzshort cn;
    cn = read_compact_number(port);
    v[l] = cn;
  }

  return o;
}

static Scheme_Object *read_compact_escape(CPort *port) 
{
#if defined(MZ_PRECISE_GC)
# define ESC_BLK_BUF_SIZE 32
  char buffer[ESC_BLK_BUF_SIZE];
#endif
  int len;
  Scheme_Object *ep;
  char *s;
  ReadParams params;
  
  len = read_compact_number(port);
  
  RANGE_CHECK_GETS((unsigned)len);
  
#if defined(MZ_PRECISE_GC)
  s = read_compact_chars(port, buffer, ESC_BLK_BUF_SIZE, len);
  if (s != buffer)
    len = -len; /* no alloc in sized_byte_string_input_port */
#else
  s = (char *)port->start + port->pos;
  port->pos += len;
  len = -len; /* no alloc in sized_byte_string_input_port */
#endif
  
  ep = scheme_make_sized_byte_string_input_port(s, len);
  
  params.can_read_compiled = 1;
  params.can_read_pipe_quote = 1;
  params.can_read_box = 1;
  params.can_read_graph = 1;
  /* Use startup value of case sensitivity so legacy code will work. */
  params.case_sensitive = scheme_case_sensitive;
  params.square_brackets_are_parens = 1;
  params.curly_braces_are_parens = 1;
  params.read_decimal_inexact = 1;
  params.can_read_dot = 1;
  params.can_read_infix_dot = 1;
  params.can_read_quasi = 1;
  params.honu_mode = 0;
  params.skip_zo_vers_check = 0;
  params.table = NULL;

  params.read_relative_path = port->relto;

  return read_inner(ep, NULL, port->ht, scheme_null, &params, 0);
}

static Scheme_Object *read_compact(CPort *port, int use_stack);

static Scheme_Object *read_compact_k(void)
{
  Scheme_Thread *p = scheme_current_thread;
  CPort *port = (CPort *)p->ku.k.p1;

  p->ku.k.p1 = NULL;

  return read_compact(port, p->ku.k.i1);
}

static Scheme_Object *read_compact(CPort *port, int use_stack)
{
#define BLK_BUF_SIZE 32
  unsigned int l;
  char *s, buffer[BLK_BUF_SIZE];
  int ch;
  Scheme_Object *v;

#ifdef DO_STACK_CHECK
  {
# include "mzstkchk.h"
    {
      Scheme_Thread *p = scheme_current_thread;
      p->ku.k.p1 = (void *)port;
      p->ku.k.i1 = use_stack;
      return scheme_handle_stack_overflow(read_compact_k);
    }
  }
#endif

  {
    ZO_CHECK(port->pos < port->size);
    ch = CP_GETC(port);

    switch(cpt_branch[ch]) {
    case CPT_ESCAPE:
      v = read_compact_escape(port);
      break;
    case CPT_SYMBOL:
      l = read_compact_number(port);
      RANGE_CHECK_GETS(l);
      s = read_compact_chars(port, buffer, BLK_BUF_SIZE, l);
      v = scheme_intern_exact_symbol(s, l);

      if (SAME_OBJ(v, port->magic_sym))
	v = port->magic_val;
      break;
    case CPT_SYMREF:
      l = read_compact_number(port);
      RANGE_CHECK(l, < port->symtab_size);
      v = port->symtab[l];
      if (v == (Scheme_Object *)-1) {
        // there is a cycle
        scheme_ill_formed_code(port);
      };
      if (!v) {
        intptr_t save_pos = port->pos;
        port->symtab[l] = (Scheme_Object *)-1; /* avoid cycles if marshaled form is broken: */
        port->pos = port->shared_offsets[l - 1];
        v = read_compact(port, 0);
        port->pos = save_pos;
        port->symtab[l] = v;
      }
      break;
    case CPT_WEIRD_SYMBOL:
      {
	int uninterned;

	uninterned = read_compact_number(port);

	l = read_compact_number(port);
	RANGE_CHECK_GETS(l);
	s = read_compact_chars(port, buffer, BLK_BUF_SIZE, l);

	if (uninterned)
	  v = scheme_make_exact_symbol(s, l);
	else
	  v = scheme_intern_exact_parallel_symbol(s, l);
        
	/* The fact that all uses of the symbol go through the table
	   means that uninterned symbols are consistently re-created for
	   a particular compiled expression. */
      }
      break;
    case CPT_KEYWORD:
      l = read_compact_number(port);
      RANGE_CHECK_GETS(l);
      s = read_compact_chars(port, buffer, BLK_BUF_SIZE, l);
      v = scheme_intern_exact_keyword(s, l);
      break;
    case CPT_BYTE_STRING:
      l = read_compact_number(port);
      RANGE_CHECK_GETS(l);
      s = read_compact_chars(port, buffer, BLK_BUF_SIZE, l);
      v = scheme_make_immutable_sized_byte_string(s, l, l < BLK_BUF_SIZE);
      break;
    case CPT_CHAR_STRING:
      {
	unsigned int el;
	mzchar *us;
	el = read_compact_number(port);
	l = read_compact_number(port);
	RANGE_CHECK_GETS(el);
	s = read_compact_chars(port, buffer, BLK_BUF_SIZE, el);
	us = (mzchar *)scheme_malloc_atomic((l + 1) * sizeof(mzchar));
	scheme_utf8_decode_all((const unsigned char *)s, el, us, 0);
	us[l] = 0;
	v = scheme_make_immutable_sized_char_string(us, l, 0);
      }
      break;
    case CPT_CHAR:
      l = read_compact_number(port);
      return scheme_make_character(l);
      break;
    case CPT_INT:
      return scheme_make_integer(read_compact_number(port));
      break;
    case CPT_NULL:
      return scheme_null;
      break;
    case CPT_TRUE:
      return scheme_true;
      break;
    case CPT_FALSE:
      return scheme_false;
      break;
    case CPT_VOID:
      return scheme_void;
      break;
    case CPT_BOX:
      v = scheme_box(read_compact(port, 0));
      SCHEME_SET_IMMUTABLE(v);
      break;
    case CPT_PAIR:
      {
	v = read_compact(port, 0);
	return scheme_make_pair(v, read_compact(port, 0));
      }
      break;
    case CPT_LIST:
      l = read_compact_number(port);
      if (l == 1) {
        v = read_compact(port, 0);
        return scheme_make_pair(v, read_compact(port, 0));
      } else
        return read_compact_list(l, 0, 0, port);
      break;
    case CPT_VECTOR:
      {
	Scheme_Object *vec;
	unsigned int i;

	l = read_compact_number(port);
	vec = scheme_make_vector(l, NULL);

	for (i = 0; i < l; i++) {
	  v = read_compact(port, 0);
	  SCHEME_VEC_ELS(vec)[i] = v;
	}

        SCHEME_SET_IMMUTABLE(vec);

	return vec;
      }
      break;
    case CPT_HASH_TABLE:
      {
	Scheme_Object *l;
	int kind, len;
        Scheme_Object *k;

	kind = read_compact_number(port);
	len = read_compact_number(port);
	
	l = scheme_null;
	while (len--) {
	  k = read_compact(port, 0);
	  v = read_compact(port, 0);
	  /* We can't always hash directly, because a key or value
	     might have a graph reference inside it. */
	  l = scheme_make_pair(scheme_make_pair(k, v), l);
	}

	if (!(*port->ht)) {
	  /* So that resolve_references is called to build the table: */
	  Scheme_Hash_Table *tht;
	  tht = scheme_make_hash_table(SCHEME_hash_ptr);
	  *(port->ht) = tht;
	}

	/* Let resolve_references complete the table construction: */
        v = scheme_alloc_object();
        v->type = scheme_table_placeholder_type;
        SCHEME_PINT_VAL(v) = kind;
        SCHEME_IPTR_VAL(v) = l;
      }
      break;
    case CPT_STX:
      {
        Scheme_Hash_Table *save_ht;

	if (!port->ut) {
          Scheme_Unmarshal_Tables *ut;
	  Scheme_Hash_Table *rht;
          char *decoded;

          ut = MALLOC_ONE_RT(Scheme_Unmarshal_Tables);
          SET_REQUIRED_TAG(ut->type = scheme_rt_unmarshal_info);
          port->ut = ut;
          ut->rp = port;
          if (port->delay_info)
            port->delay_info->ut = ut;

          decoded = (char *)scheme_malloc_atomic(port->symtab_size);
          memset(decoded, 0, port->symtab_size);
          ut->decoded = decoded;

	  rht = scheme_make_hash_table(SCHEME_hash_ptr);
	  port->ut->rns = rht;
	}

        save_ht = *port->ht;
        *port->ht = NULL;

	v = read_compact(port, 1);

        if (*port->ht) {
          *port->ht = NULL;
          v = resolve_references(v, port->orig_port, NULL,
                                 scheme_make_hash_table(SCHEME_hash_ptr), 
                                 scheme_make_hash_table(SCHEME_hash_ptr), 
                                 0, 0);
        }

        *port->ht = save_ht;

	v = scheme_unmarshal_datum_to_syntax(v, port->ut, 0);
	scheme_num_read_syntax_objects++;
	if (!v)
	  scheme_ill_formed_code(port);
      }
      break;
    case CPT_MARSHALLED:
      v = read_marshalled(read_compact_number(port), port);
      break;
    case CPT_QUOTE:
      v = read_compact_quote(port, 1);
      break;
    case CPT_REFERENCE:
      l = read_compact_number(port);
      RANGE_CHECK(l, < (EXPECTED_PRIM_COUNT 
                        + EXPECTED_UNSAFE_COUNT 
                        + EXPECTED_FLFXNUM_COUNT 
                        + EXPECTED_FUTURES_COUNT));
      return variable_references[l];
      break;
    case CPT_LOCAL:
      {
	int p, flags;
	p = read_compact_number(port);
        if (p < 0) {
          p = -(p + 1);
          flags = read_compact_number(port);
        } else
          flags = 0;
	return scheme_make_local(scheme_local_type, p, flags);
      }
      break;
    case CPT_LOCAL_UNBOX:
      {
	int p, flags;
	p = read_compact_number(port);
        if (p < 0) {
          p = -(p + 1);
          flags = read_compact_number(port);
        } else
          flags = 0;
	return scheme_make_local(scheme_local_unbox_type, p, flags);
      }
      break;
    case CPT_SVECTOR:
      {
	int l;
	l = read_compact_number(port);
	v = read_compact_svector(port, l);
      }
      break;
    case CPT_APPLICATION:
      {
	int c, i;
	Scheme_App_Rec *a;

	c = read_compact_number(port) + 1;

	a = scheme_malloc_application(c);
	for (i = 0; i < c; i++) {
	  v = read_compact(port, 1);
	  a->args[i] = v;
	}

	scheme_finish_application(a);
	return (Scheme_Object *)a;
      }
      break;
    case CPT_LET_ONE:
    case CPT_LET_ONE_FLONUM:
    case CPT_LET_ONE_UNUSED:
      {
	Scheme_Let_One *lo;
	int et;

	lo = (Scheme_Let_One *)scheme_malloc_tagged(sizeof(Scheme_Let_One));
	lo->iso.so.type = scheme_let_one_type;

	v = read_compact(port, 1);
        lo->value = v;
	v = read_compact(port, 1);
	lo->body = v;
	et = scheme_get_eval_type(lo->value);
        if (ch == CPT_LET_ONE_FLONUM)
          et |= LET_ONE_FLONUM;
        if (ch == CPT_LET_ONE_UNUSED)
          et |= LET_ONE_UNUSED;
        SCHEME_LET_EVAL_TYPE(lo) = et;
	
	return (Scheme_Object *)lo;
      }
      break;
    case CPT_BRANCH:
      {
	Scheme_Object *test, *tbranch, *fbranch;
	test = read_compact(port, 1);
	tbranch = read_compact(port, 1);
	fbranch = read_compact(port, 1);
	return scheme_make_branch(test, tbranch, fbranch);
      }
      break;
    case CPT_MODULE_INDEX:
	{
	  Scheme_Object *path, *base;

	  path = read_compact(port, 0);
	  base = read_compact(port, 0);

	  return scheme_make_modidx(path, base, scheme_false);
	}
	break;
    case CPT_MODULE_VAR:
      {
	Module_Variable *mv;
	Scheme_Object *mod, *var;
	int pos;

	mod = read_compact(port, 0);
	var = read_compact(port, 0);
	pos = read_compact_number(port);

	mv = MALLOC_ONE_TAGGED(Module_Variable);
	mv->so.type = scheme_module_variable_type;
        if (SCHEME_SYMBOLP(mod))
          mod = scheme_intern_resolved_module_path(mod);
	mv->modidx = mod;
	mv->sym = var;
        if (pos == -2) {
          mv->mod_phase = 1;
          pos = read_compact_number(port);
          mv->pos = pos;
        } else
          mv->pos = pos;

	return (Scheme_Object *)mv;
      }
      break;
    case CPT_PATH:
      {
	l = read_compact_number(port);
	RANGE_CHECK_GETS(l);
	s = read_compact_chars(port, buffer, BLK_BUF_SIZE, l);
	v = scheme_make_sized_path(s, l, l < BLK_BUF_SIZE);

	if (scheme_is_relative_path(SCHEME_PATH_VAL(v), SCHEME_PATH_LEN(v), SCHEME_PLATFORM_PATH_KIND)) {
	  /* Resolve relative path using the current load-relative directory: */
	  if (SCHEME_PATHP(port->relto)) {
	    Scheme_Object *a[2];
	    a[0] = port->relto;
	    a[1] = v;
	    v = scheme_build_path(2, a);
	  }
	}
      }
      break;
    case CPT_CLOSURE:
      {
        Scheme_Closure *cl;
        l = read_compact_number(port);
        RANGE_CHECK(l, < port->symtab_size);
        cl = scheme_malloc_empty_closure();
        port->symtab[l] = (Scheme_Object *)cl;
        v = read_compact(port, 0);
        if (!SAME_TYPE(SCHEME_TYPE(v), scheme_closure_type)
            || ((Scheme_Closure *)v)->code->closure_size) {
          scheme_ill_formed_code(port);
          return NULL;
        }
        cl->code = ((Scheme_Closure *)v)->code;
        return (Scheme_Object *)cl;
        break;
      }
    case CPT_DELAY_REF:
      {
        l = read_compact_number(port);
        RANGE_CHECK(l, < port->symtab_size);
        v = port->symtab[l];
        if (!v) {
          if (port->delay_info) {
            /* This is where we construct information for
               loading the syntax object on demand. */
            v = scheme_make_raw_pair(scheme_make_integer(l),
                                     (Scheme_Object *)port->delay_info);
          } else {
            intptr_t save_pos = port->pos;
            port->symtab[l] = scheme_false; /* avoid cycles if marshaled form is broken: */
            port->pos = port->shared_offsets[l - 1];
            v = read_compact(port, 0);
            port->pos = save_pos;
            port->symtab[l] = v;
          }
        }
        return v;
        break;
      }
    case CPT_PREFAB:
      {
        Scheme_Struct_Type *st;
        v = read_compact(port, 0);
        if (!SCHEME_VECTORP(v) || !SCHEME_VEC_SIZE(v))
          v = NULL;
        else {
          st = scheme_lookup_prefab_type(SCHEME_VEC_ELS(v)[0], SCHEME_VEC_SIZE(v) - 1);
          if (!st || (st->num_slots != (SCHEME_VEC_SIZE(v) - 1)))
            v = NULL;
          else {
            v = scheme_make_prefab_struct_instance(st, v);
          }
        }
        break;
      }
    case CPT_SMALL_LOCAL_START:
    case CPT_SMALL_LOCAL_UNBOX_START:
      {
	Scheme_Type type;

	if (CPT_BETWEEN(ch, SMALL_LOCAL_UNBOX)) {
	  type = scheme_local_unbox_type;
	  ch -= CPT_SMALL_LOCAL_UNBOX_START;
	} else {
	  type = scheme_local_type;
	  ch -= CPT_SMALL_LOCAL_START;
	}
	return scheme_make_local(type, ch, 0);
      }
      break;
    case CPT_SMALL_MARSHALLED_START:
      {
	l = ch - CPT_SMALL_MARSHALLED_START;
	v = read_marshalled(l, port);
      }
      break;
    case CPT_SMALL_SYMBOL_START:
      {
	l = ch - CPT_SMALL_SYMBOL_START;
	RANGE_CHECK_GETS(l);
	s = read_compact_chars(port, buffer, BLK_BUF_SIZE, l);
	v = scheme_intern_exact_symbol(s, l);

	if (SAME_OBJ(v, port->magic_sym))
	  v = port->magic_val;
      }
      break;
    case CPT_SMALL_NUMBER_START:
      {
	l = ch - CPT_SMALL_NUMBER_START;
	return scheme_make_integer(l);
      }
      break;
    case CPT_SMALL_SVECTOR_START:
      {
	l = ch - CPT_SMALL_SVECTOR_START;
	v = read_compact_svector(port, l);
      }
      break;
    case CPT_SMALL_PROPER_LIST_START:
    case CPT_SMALL_LIST_START:
      {
	int ppr = CPT_BETWEEN(ch, SMALL_PROPER_LIST);
	l = ch - (ppr ? CPT_SMALL_PROPER_LIST_START : CPT_SMALL_LIST_START);
      	if (l == 1) {
          Scheme_Object *cdr;
          v = read_compact(port, 0);
          cdr = (ppr
                 ? scheme_null
                 : read_compact(port, 0));
          return scheme_make_pair(v, cdr);
        } else
          return read_compact_list(l, ppr, /* use_stack */ 0, port);
      }
      break;
    case CPT_SMALL_APPLICATION_START:
      {
	int c, i;
	Scheme_App_Rec *a;

	c = (ch - CPT_SMALL_APPLICATION_START) + 1;

	a = scheme_malloc_application(c);
	for (i = 0; i < c; i++) {
	  v = read_compact(port, 1);
	  a->args[i] = v;
	}

	scheme_finish_application(a);

	return (Scheme_Object *)a;
      }
      break;
    case CPT_SMALL_APPLICATION2:
      {
	short et;
	Scheme_App2_Rec *app;

	app = MALLOC_ONE_TAGGED(Scheme_App2_Rec);
	app->iso.so.type = scheme_application2_type;

	v = read_compact(port, 1);
	app->rator = v;
	v = read_compact(port, 1);
	app->rand = v;

	et = scheme_get_eval_type(app->rand);
	et = et << 3;
	et += scheme_get_eval_type(app->rator);
	SCHEME_APPN_FLAGS(app) = et;

	return (Scheme_Object *)app;
      }
      break;
    case CPT_SMALL_APPLICATION3:
      {
	short et;
	Scheme_App3_Rec *app;

	app = MALLOC_ONE_TAGGED(Scheme_App3_Rec);
	app->iso.so.type = scheme_application3_type;

	v = read_compact(port, 1);
	app->rator = v;
	v = read_compact(port, 1);
	app->rand1 = v;
	v = read_compact(port, 1);
	app->rand2 = v;

	et = scheme_get_eval_type(app->rand2);
	et = et << 3;
	et += scheme_get_eval_type(app->rand1);
	et = et << 3;
	et += scheme_get_eval_type(app->rator);
	SCHEME_APPN_FLAGS(app) = et;

	return (Scheme_Object *)app;
      }
      break;
    default:
      v = NULL;
      break;
    }

    /* Some cases where v != NULL return directly */

    if (!v)
      scheme_ill_formed_code(port);
  }

  return v;
}

static Scheme_Object *read_compact_list(int c, int proper, int use_stack, CPort *port)
{
  Scheme_Object *v, *first, *last, *pair;

  v = read_compact(port, 0);
  last = scheme_make_pair(v, scheme_null);

  first = last;

  while (--c) {
    v = read_compact(port, 0);

    pair = scheme_make_pair(v, scheme_null);

    SCHEME_CDR(last) = pair;
    last = pair;
  }

  if (!proper) {
    v = read_compact(port, 0);
    SCHEME_CDR(last) = v;
  }

  return first;
}

static Scheme_Object *read_compact_quote(CPort *port, int embedded)
{
  Scheme_Hash_Table **q_ht, **old_ht;
  Scheme_Object *v;

  /* Use a new hash table. A compiled quoted form may have graph
     structure, but only local graph structure is allowed. */
  q_ht = MALLOC_N(Scheme_Hash_Table *, 1);
  *q_ht = NULL;

  old_ht = port->ht;
  port->ht = q_ht;

  v = read_compact(port, 0);

  port->ht = old_ht;

  if (*q_ht)
    v = resolve_references(v, port->orig_port, NULL,
                           scheme_make_hash_table(SCHEME_hash_ptr), 
                           scheme_make_hash_table(SCHEME_hash_ptr), 
                           0, 0);

  return v;
}

static Scheme_Object *read_marshalled(int type, CPort *port)
{
  Scheme_Object *l;
  Scheme_Type_Reader reader;

  l = read_compact(port, 1);

  if ((type < 0) || (type >= _scheme_last_type_)) {
    scheme_ill_formed_code(port);
  }

  reader = scheme_type_readers[type];

  if (!reader) {
    scheme_ill_formed_code(port);
  }

  l = reader(l);

  if (!l)
    scheme_ill_formed_code(port);

  return l;
}

static intptr_t read_simple_number_from_port(Scheme_Object *port)
{
  intptr_t a, b, c, d;

  a = (unsigned char)scheme_get_byte(port);
  b = (unsigned char)scheme_get_byte(port);
  c = (unsigned char)scheme_get_byte(port);
  d = (unsigned char)scheme_get_byte(port);

  return (a
          + (b << 8)
          + (c << 16)
          + (d << 24));
}

/* "#~" has been read */
static Scheme_Object *read_compiled(Scheme_Object *port,
				    Scheme_Object *stxsrc,
				    intptr_t line, intptr_t col, intptr_t pos,
				    Scheme_Hash_Table **ht,
				    ReadParams *params)
{
  Scheme_Object *result;
  intptr_t size, shared_size, got, offset = 0;
  CPort *rp;
  intptr_t symtabsize;
  Scheme_Object **symtab;
  intptr_t *so;
  Scheme_Load_Delay *delay_info;
  Scheme_Hash_Table **local_ht;
  int all_short;
  int perma_cache = use_perma_cache;
  Scheme_Object *dir;
  Scheme_Config *config;
  char hash_code[20];
	  
  /* Allow delays? */
  if (params->delay_load_info) {
    delay_info = MALLOC_ONE_RT(Scheme_Load_Delay);
    SET_REQUIRED_TAG(delay_info->type = scheme_rt_delay_load_info);
    delay_info->path = params->delay_load_info;
  } else
    delay_info = NULL;

  /* Check version: */
  size = scheme_get_byte(port);
  {
    char buf[64];

    if (size < 0) size = 0;
    if (size > 63) size = 63;

    got = scheme_get_bytes(port, size, buf, 0);
    buf[got] = 0;

    if (!params->skip_zo_vers_check)
      if (strcmp(buf, MZSCHEME_VERSION))
        scheme_read_err(port, stxsrc, line, col, pos, got, 0, NULL,
                        "read (compiled): code compiled for version %s, not %s",
                        (buf[0] ? buf : "???"), MZSCHEME_VERSION);
  }
  offset += size + 1;

  /* Module hash code */
  got = scheme_get_bytes(port, 20, hash_code, 0);
  offset += 20;

  symtabsize = read_simple_number_from_port(port);
  offset += 4;
  
  /* Load table mapping symtab indices to stream positions: */

  all_short = scheme_get_byte(port);
  so = (intptr_t *)scheme_malloc_fail_ok(scheme_malloc_atomic, sizeof(intptr_t) * symtabsize);
  if ((got = scheme_get_bytes(port, (all_short ? 2 : 4) * (symtabsize - 1), (char *)so, 0)) 
      != ((all_short ? 2 : 4) * (symtabsize - 1)))
    scheme_read_err(port, NULL, -1, -1, -1, -1, 0, NULL,
		    "read (compiled): ill-formed code (bad table count: %ld != %ld)",
		    got, (all_short ? 2 : 4) * (symtabsize - 1));
  offset += got;

  {
    /* This loop runs top to bottom, since sizeof(long) may be larger
       than the decoded integers (but it's never shorter) */
    intptr_t j, v;
    unsigned char *so_c = (unsigned char *)so;
    for (j = symtabsize - 1; j--; ) {
      if (all_short) {
        v = so_c[j * 2]
          + (so_c[j * 2 + 1] << 8);
      } else {
        v = so_c[j * 4]
          + (so_c[j * 4 + 1] << 8)
          + (so_c[j * 4 + 2] << 16)
          + (so_c[j * 4 + 3] << 24);
      }
      so[j] = v;
    }
  }

  /* Continue reading content */

  shared_size = read_simple_number_from_port(port);
  size = read_simple_number_from_port(port);

  if (shared_size >= size) {
    scheme_read_err(port, NULL, -1, -1, -1, -1, 0, NULL,
		    "read (compiled): ill-formed code (shared size %ld >= total size %ld)",
		    shared_size, size);
  }

  offset += 8;

  rp = MALLOC_ONE_RT(CPort);
  SET_REQUIRED_TAG(rp->type = scheme_rt_compact_port);
  {
    unsigned char *st;
    st = (unsigned char *)scheme_malloc_fail_ok(scheme_malloc_atomic, size + 1);
    rp->start = st;
  }
  rp->pos = 0;
  {
    intptr_t base;
    scheme_tell_all(port, NULL, NULL, &base);
    rp->base = base;
  }
  rp->orig_port = port;
  rp->size = size;
  if ((got = scheme_get_bytes(port, size, (char *)rp->start, 0)) != size)
    scheme_read_err(port, NULL, -1, -1, -1, -1, 0, NULL,
		    "read (compiled): ill-formed code (bad count: %ld != %ld"
                    ", started at %ld)",
		    got, size, rp->base);

  local_ht = MALLOC_N(Scheme_Hash_Table *, 1);

  symtab = MALLOC_N(Scheme_Object *, symtabsize);
  rp->symtab_size = symtabsize;
  rp->ht = local_ht;
  rp->symtab = symtab;

  config = scheme_current_config();

  dir = scheme_get_param(config, MZCONFIG_LOAD_DIRECTORY);
  rp->relto = dir;

  rp->magic_sym = params->magic_sym;
  rp->magic_val = params->magic_val;

  rp->shared_offsets = so;
  rp->delay_info = delay_info;

  if (!delay_info) {
    /* Read shared parts: */
    intptr_t j, len;
    Scheme_Object *v;
    len = symtabsize;
    for (j = 1; j < len; j++) {
      if (!symtab[j]) {
        v = read_compact(rp, 0);
        symtab[j] = v;
      } else {
        if (j+1 < len)
          rp->pos = so[j];
        else
          rp->pos = shared_size;
      }
    }
  } else {
    scheme_reserve_file_descriptor();
    rp->pos = shared_size; /* skip shared part */
    delay_info->file_offset = offset + 2 + 1; /* +2 is for #~; +1 is ???? */
    delay_info->size = shared_size;
    delay_info->symtab_size = rp->symtab_size;
    delay_info->symtab = rp->symtab;
    delay_info->shared_offsets = rp->shared_offsets;
    delay_info->relto = rp->relto;

    if (perma_cache) {
      unsigned char *cache;
      cache = (unsigned char *)scheme_malloc_atomic(shared_size);
      memcpy(cache, rp->start, shared_size);
      delay_info->cached = cache;
      delay_info->cached_port = port;
      delay_info->perma_cache = 1;
    }
  }

  /* Read main body: */
  result = read_marshalled(scheme_compilation_top_type, rp);

  if (delay_info)
    if (delay_info->ut)
      delay_info->ut->rp = NULL; /* clean up */

  if (*local_ht) {
    scheme_read_err(port, NULL, -1, -1, -1, -1, 0, NULL,
		    "read (compiled): ill-formed code (unexpected graph structure)");
    return NULL;
  }

  if (SAME_TYPE(SCHEME_TYPE(result), scheme_compilation_top_type)) {
    Scheme_Compilation_Top *top = (Scheme_Compilation_Top *)result;

    scheme_validate_code(rp, top->code,
			 top->max_let_depth,
			 top->prefix->num_toplevels,
			 top->prefix->num_stxes,
			 top->prefix->num_lifts,
                         NULL,
                         0);
    /* If no exception, the resulting code is ok. */

    /* Install module hash code, if any. This code is used to register
       the module in scheme_module_execute(), and it's used to
       find a registered module in the default load handler. */
    {
      int i;
      for (i = 0; i < 20; i++) {
        if (hash_code[i]) break;
      }

      if (i < 20) {
        Scheme_Module *m;
        m = scheme_extract_compiled_module(result);
        if (m) {
          Scheme_Object *hc;
          hc = scheme_make_sized_byte_string(hash_code, 20, 1);
          hc = scheme_make_pair(hc, dir);

          m->code_key = hc;
        }
      }
    }
  } else
    scheme_ill_formed_code(rp);

  return result;
}


THREAD_LOCAL_DECL(static Scheme_Load_Delay *clear_bytes_chain);

void scheme_clear_delayed_load_cache()
{
  Scheme_Load_Delay *next;

  while (clear_bytes_chain) {
    next = clear_bytes_chain->clear_bytes_next;
    clear_bytes_chain->cached = NULL;
    clear_bytes_chain->cached_port = NULL;
    clear_bytes_chain->clear_bytes_next = NULL;
    clear_bytes_chain->clear_bytes_prev = NULL;
    clear_bytes_chain = next;
  }
}

Scheme_Object *scheme_load_delayed_code(int _which, Scheme_Load_Delay *_delay_info)
{
  Scheme_Load_Delay * volatile delay_info = _delay_info;
  CPort *rp;
  CPort * volatile old_rp;
  volatile int which = _which;
  intptr_t size, got;
  unsigned char *st;
  Scheme_Object * volatile port;
  Scheme_Object * volatile v;
  Scheme_Object * volatile v_exn;
  Scheme_Hash_Table ** volatile ht;
  mz_jmp_buf newbuf, * volatile savebuf;

  /* Remove from cache-clearing chain: */
  if (!delay_info->perma_cache) {
    if (delay_info->clear_bytes_prev)
      delay_info->clear_bytes_prev->clear_bytes_next = delay_info->clear_bytes_next;
    else if (clear_bytes_chain == delay_info)
      clear_bytes_chain = delay_info->clear_bytes_next;
    if (delay_info->clear_bytes_next)
      delay_info->clear_bytes_next->clear_bytes_prev = delay_info->clear_bytes_prev;
    
    delay_info->clear_bytes_prev = NULL;
    delay_info->clear_bytes_next = NULL;
  }

  size = delay_info->size;

  /* Load in file bytes: */
  if (!delay_info->cached) {
    Scheme_Object *a[1];

    scheme_start_atomic();
    scheme_release_file_descriptor();

    a[0] = delay_info->path;
    port = scheme_do_open_input_file("on-demand-loader", 0, 1, a, 0);

    savebuf = scheme_current_thread->error_buf;
    scheme_current_thread->error_buf = &newbuf;
    if (scheme_setjmp(newbuf)) {
      scheme_end_atomic_no_swap();
      scheme_close_input_port(port);
      scheme_current_thread->error_buf = savebuf;
      scheme_longjmp(*savebuf, 1);
      return NULL;
    } else {
      st = (unsigned char *)scheme_malloc_atomic(size + 1);

      scheme_set_file_position(port, delay_info->file_offset);
      
      if ((got = scheme_get_bytes(port, size, (char *)st, 0)) != size)
        scheme_read_err(port, NULL, -1, -1, -1, -1, 0, NULL,
                        "on-demand load: ill-formed code (bad count: %ld != %ld"
                        ", started at %ld)",
                        got, size, 0);
    }
    scheme_current_thread->error_buf = savebuf;

    scheme_close_input_port(port);
    scheme_reserve_file_descriptor();

    scheme_end_atomic_no_swap();

    delay_info->cached = st;
    delay_info->cached_port = port;
  } else {
    port = delay_info->cached_port;
  }

  /* Allow only one thread at a time. This is a little questionable,
     because unmarshalling could take arbitrarily long, and an
     untrusted program might construct an adversarial bytecode. That
     would be relatively difficult, though. In practice, unmarshalling
     will be fast. */
  scheme_start_atomic();

  old_rp = delay_info->current_rp;

  /* Create a port for reading: */
  rp = MALLOC_ONE_RT(CPort);
  SET_REQUIRED_TAG(rp->type = scheme_rt_compact_port);
  rp->start = delay_info->cached;
  rp->pos = 0;
  rp->base = 0;
  rp->orig_port = port;
  rp->size = size;
  rp->ut = delay_info->ut;
  if (delay_info->ut)
    delay_info->ut->rp = rp;

  ht = MALLOC_N(Scheme_Hash_Table *, 1);

  rp->symtab_size = delay_info->symtab_size;
  rp->ht = ht;
  rp->symtab = delay_info->symtab;
  rp->relto = delay_info->relto;
  rp->shared_offsets = delay_info->shared_offsets;
  rp->delay_info = delay_info;

  rp->pos = delay_info->shared_offsets[which - 1];

  /* Perform the read, catching escapes so we can clean up: */
  savebuf = scheme_current_thread->error_buf;
  scheme_current_thread->error_buf = &newbuf;
  scheme_current_thread->reading_delayed = scheme_true;
  if (scheme_setjmp(newbuf)) {
    v = NULL;
    v_exn = scheme_current_thread->reading_delayed;
  } else {
    v = read_compact(rp, 0);
    v_exn = NULL;
  }
  scheme_current_thread->error_buf = savebuf;
  scheme_current_thread->reading_delayed = NULL;

  /* Clean up: */

  delay_info->current_rp = old_rp;
  if (delay_info->ut)
    delay_info->ut->rp = old_rp;

  if (!old_rp && !delay_info->perma_cache) {
    /* No one using the cache, to register it to be cleaned up */
    delay_info->clear_bytes_next = clear_bytes_chain;
    if (clear_bytes_chain)
      clear_bytes_chain->clear_bytes_prev = delay_info;
    clear_bytes_chain = delay_info;
  }

  scheme_end_atomic_no_swap();
  
  if (v) {
    if (*ht) {
      v = resolve_references(v, port, NULL,
                             scheme_make_hash_table(SCHEME_hash_ptr), 
                             scheme_make_hash_table(SCHEME_hash_ptr), 
                             0, 0);
    }

    delay_info->symtab[which] = v;
        
    return v;
  } else {
    if (v_exn && !scheme_current_thread->cjs.is_kill)
      scheme_raise(v_exn);
    scheme_longjmp(*scheme_current_thread->error_buf, 1);
    return NULL;
  }
}

Scheme_Object *scheme_unmarshal_wrap_get(Scheme_Unmarshal_Tables *ut, 
                                         Scheme_Object *wraps_key, 
                                         int *_decoded)
{
  intptr_t l;
  l = SCHEME_INT_VAL(wraps_key);

  if ((l < 0) || ((uintptr_t)l >= ut->rp->symtab_size))
    scheme_ill_formed_code(ut->rp);

  if (!ut->rp->symtab[l]) {
    Scheme_Object *v;
    intptr_t save_pos;

    if (!ut->rp->delay_info)
      scheme_ill_formed_code(ut->rp);

    save_pos = ut->rp->pos;
    ut->rp->pos = ut->rp->shared_offsets[l - 1];
    v = read_compact(ut->rp, 0);
    ut->rp->pos = save_pos;
    ut->rp->symtab[l] = v;
  }

  *_decoded = ut->decoded[l];
  return ut->rp->symtab[l];
}

void scheme_unmarshal_wrap_set(Scheme_Unmarshal_Tables *ut, 
                               Scheme_Object *wraps_key, 
                               Scheme_Object *v)
{
  intptr_t l;
  l = SCHEME_INT_VAL(wraps_key);

  ut->rp->symtab[l] = v;
  ut->decoded[l] = 1;
}

/*========================================================================*/
/*                           readtable support                            */
/*========================================================================*/

Scheme_Object *scheme_make_default_readtable()
{
  return scheme_false;
}

static int readtable_kind(Readtable *t, int ch, ReadParams *params)
{
  int k;
  Scheme_Object *v;

  if (ch < 128)
    k = t->fast_mapping[ch];
  else {
    v = scheme_hash_get(t->mapping, scheme_make_integer(ch));
    if (!v) {
      if (scheme_isspace(ch))
	k = READTABLE_WHITESPACE;
      else
	k = READTABLE_CONTINUING;
    } else
      k = SCHEME_INT_VAL(SCHEME_CAR(v));
  }

  if (k == READTABLE_MAPPED) {
    /* ch is mapped to a default behavior: */
    v = scheme_hash_get(t->mapping, scheme_make_integer(ch));
    ch = SCHEME_INT_VAL(SCHEME_CDR(v));
    if (ch < 128)
      k = builtin_fast[ch];
    else if (scheme_isspace(ch))
      k = READTABLE_WHITESPACE;
    else
      k = READTABLE_CONTINUING;
  }

  if (k == READTABLE_MULTIPLE_ESCAPE) {
    /* This is the only one sensitive to params. */
    if (!params->can_read_pipe_quote)
      return READTABLE_CONTINUING;
  }

  return k;
}

static Scheme_Object *readtable_call(int w_char, int ch, Scheme_Object *proc, ReadParams *params,
				     Scheme_Object *port, Scheme_Object *src, intptr_t line, intptr_t col, intptr_t pos,
				     int get_info, 
                                     Scheme_Hash_Table **ht, Scheme_Object *modpath_stx)
{
  int cnt, add_srcloc = 0;
  Scheme_Object *a[6], *v;
  Scheme_Cont_Frame_Data cframe;
  
  if (w_char) {
    a[0] = scheme_make_character(ch);
    a[1] = port;
    a[2] = proc;
    if (!src && scheme_check_proc_arity(NULL, 2, 2, 3, a)) {
      cnt = 2;
    } else {
      cnt = 6;
      a[2] = (src ? src : scheme_false);
      add_srcloc = 3;
    }
  } else {
    if (src) {
      a[0] = src;
      a[1] = port;
      if (modpath_stx) {
        a[2] = modpath_stx;
        add_srcloc = 3;
        cnt = 6;
      } else
        cnt = 2;
    } else {
      a[0] = port;
      if (modpath_stx) {
        a[1] = modpath_stx;
        add_srcloc = 2;
        cnt = 5;
      } else
        cnt = 1;
    }
  }

  if (add_srcloc) {
    a[add_srcloc + 0] = (line > 0) ? scheme_make_integer(line) : scheme_false;
    a[add_srcloc + 1] = (col > 0) ? scheme_make_integer(col-1) : scheme_false;
    a[add_srcloc + 2] = (pos > 0) ? scheme_make_integer(pos) : scheme_false;
  }

  if (src) {
    /* fresh ht in case nested uses recursive `read' instead of recursive `read-syntax': */
    ht = MALLOC_N(Scheme_Hash_Table *, 1);
  }

  if (!get_info) {
    scheme_push_continuation_frame(&cframe);
    scheme_set_in_read_mark(src, ht);
  }

  v = scheme_apply(proc, cnt, a);

  if (get_info) {
    a[0] = v;
    if (!scheme_check_proc_arity(NULL, 2, 0, 1, a)) {
      scheme_wrong_type("read-language", "procedure (arity 2)", -1, -1, a);
    }
  }

  if (!get_info) {
    scheme_pop_continuation_frame(&cframe);
  }

  if (!get_info && !scheme_special_comment_value(v)) {
    if (SCHEME_STXP(v)) {
      if (!src)
	v = scheme_syntax_to_datum(v, 0, NULL);
    } else if (src) {
      Scheme_Object *s;

      if (*ht) {
        /* resolve references from recursive `read': */
        v = resolve_references(v, port, NULL,
                               scheme_make_hash_table(SCHEME_hash_ptr), 
                               scheme_make_hash_table(SCHEME_hash_ptr), 
                               1, 0);
      }

      s = scheme_make_stx_w_offset(scheme_false, line, col, pos, SPAN(port, pos), src, STX_SRCTAG);
      v = scheme_datum_to_syntax(v, s, scheme_false, 1, 1);
    }

    if (!src)
      set_need_copy(ht);
  }
  
  return v;
}

void scheme_set_in_read_mark(Scheme_Object *src, Scheme_Hash_Table **ht)
{
  Scheme_Object *v;

  if (ht)
    v = scheme_make_raw_pair((Scheme_Object *)ht, 
			     (src ? scheme_true : scheme_false));
  else
    v = scheme_false;
  scheme_set_cont_mark(unresolved_uninterned_symbol, v);
}

static Scheme_Object *readtable_handle(Readtable *t, int *_ch, int *_use_default, ReadParams *params,
				       Scheme_Object *port, Scheme_Object *src, intptr_t line, intptr_t col, intptr_t pos,
				       Scheme_Hash_Table **ht)
{
  int ch = *_ch;
  Scheme_Object *v;

  v = scheme_hash_get(t->mapping, scheme_make_integer(ch));

  if (!v) {
    *_use_default = 1;
    return NULL;
  }

  if (SCHEME_INT_VAL(SCHEME_CAR(v)) == READTABLE_MAPPED) {
    *_ch = SCHEME_INT_VAL(SCHEME_CDR(v));
    *_use_default = 1;
    return NULL;
  }

  *_use_default = 0;

  v = SCHEME_CDR(v);

  v = readtable_call(1, ch, v, params, port, src, line, col, pos, 0, ht, NULL);
  
  return v;
}

static int readtable_effective_char(Readtable *t, int ch)
{
  Scheme_Object *v;

  if (!t) return ch;

  v = scheme_hash_get(t->mapping, scheme_make_integer(ch));

  if (v) {
    if (SCHEME_INT_VAL(SCHEME_CAR(v)) == READTABLE_MAPPED)
      return SCHEME_INT_VAL(SCHEME_CDR(v));
    return 0; /* not equivalent to any standard char mapping */
  } else
    return ch;
}

static Scheme_Object *readtable_handle_hash(Readtable *t, int ch, int *_use_default, ReadParams *params,
					    Scheme_Object *port, Scheme_Object *src, intptr_t line, intptr_t col, intptr_t pos,
					    Scheme_Hash_Table **ht)
{
  Scheme_Object *v;

  v = scheme_hash_get(t->mapping, scheme_make_integer(-ch));

  if (!v) {
    *_use_default = 1;
    return NULL;
  }

  *_use_default = 0;

  v = readtable_call(1, ch, v, params, port, src, line, col, pos, 0, ht, NULL);

  if (scheme_special_comment_value(v))
    return NULL;
  else
    return v;
}

static Scheme_Object *make_readtable(int argc, Scheme_Object **argv)
{
  Scheme_Object *sym, *val;
  Readtable *t, *orig_t;
  Scheme_Hash_Table *ht;
  char *fast;
  int i, ch;

  if (SCHEME_FALSEP(argv[0]))
    orig_t = NULL;
  else {
    if (!SAME_TYPE(scheme_readtable_type, SCHEME_TYPE(argv[0]))) {
      scheme_wrong_type("make-readtable", "readtable or #f", 0, argc, argv);
      return NULL;
    }
    orig_t = (Readtable *)argv[0];
  }

  t = MALLOC_ONE_TAGGED(Readtable);
  t->so.type = scheme_readtable_type;
  if (orig_t)
    ht = scheme_clone_hash_table(orig_t->mapping);
  else
    ht = scheme_make_hash_table(SCHEME_hash_ptr);
  t->mapping = ht;
  fast = scheme_malloc_atomic(128);
  memcpy(fast, (orig_t ? orig_t->fast_mapping : builtin_fast), 128);
  t->fast_mapping = fast;
  t->symbol_parser = (orig_t ? orig_t->symbol_parser : NULL);

  for (i = 1; i < argc; i += 3) {
    if (!SCHEME_FALSEP(argv[i]) && !SCHEME_CHARP(argv[i])) {
      scheme_wrong_type("make-readtable", "character or #f", i, argc, argv);
      return NULL;
    }

    if (i + 1 >= argc) {
      if (SCHEME_FALSEP(argv[i]))
	scheme_arg_mismatch("make-readtable",
			    "expected 'non-terminating-macro after #f",
			    NULL);
      else
	scheme_arg_mismatch("make-readtable",
			    "expected 'terminating-macro, 'non-terminating-macro, 'dispatch-macro,"
			    " or character argument after character argument: ",
			    argv[i]);
    }

    sym = argv[i + 1];
    if (!SAME_OBJ(sym, terminating_macro_symbol)
	&& !SAME_OBJ(sym, non_terminating_macro_symbol)
	&& !SAME_OBJ(sym, dispatch_macro_symbol)
	&& !SCHEME_CHARP(sym)) {
      scheme_wrong_type("make-readtable", 
			"'terminating-macro, 'non-terminating-macro, 'dispatch-macro, or character", 
			i+1, argc, argv);
      return NULL;
    }
    if (SCHEME_FALSEP(argv[i])
	&& !SAME_OBJ(sym, non_terminating_macro_symbol)) {
      scheme_arg_mismatch("make-readtable",
			  "expected 'non-terminating-macro after #f, given: ",
			  sym);
    }

    if (i + 2 >= argc) {
      scheme_arg_mismatch("make-readtable",
			  (SCHEME_CHARP(sym) 
			   ? "expected readtable or #f argument after character argument, given: "
			   : "expected procedure argument after symbol argument, given: "),
			  argv[i+1]);
    }

    if (SCHEME_FALSEP(argv[i])) {
      scheme_check_proc_arity("make-readtable", 6, i+2, argc, argv);
      t->symbol_parser = argv[i + 2];
    } else if (SAME_OBJ(sym, dispatch_macro_symbol)) {
      ch = SCHEME_CHAR_VAL(argv[i]);
      scheme_check_proc_arity("make-readtable", 6, i+2, argc, argv);
      scheme_hash_set(t->mapping, scheme_make_integer(-ch), argv[i+2]);
    } else {
      if (SCHEME_CHARP(sym)) {
	Readtable *src;
	int sch;

	if (SCHEME_FALSEP(argv[i+2])) {
	  src = NULL;
	} else {
	  if (!SAME_TYPE(scheme_readtable_type, SCHEME_TYPE(argv[i+2]))) {
	    scheme_wrong_type("make-readtable", "readtable or #f", i+2, argc, argv);
	    return NULL;
	  }
	  src = (Readtable *)(argv[i+2]);
	}
	sch = SCHEME_CHAR_VAL(argv[i+1]);
	if (!src)
	  val = NULL; /* use default */
	else
	  val = scheme_hash_get(src->mapping, scheme_make_integer(sch));
	if (!val)
	  val = scheme_make_pair(scheme_make_integer(READTABLE_MAPPED), scheme_make_integer(sch));
      } else {
	int kind;
	scheme_check_proc_arity("make-readtable", 6, i+2, argc, argv);
	kind = (SAME_OBJ(sym, non_terminating_macro_symbol)
		? READTABLE_CONTINUING
		: READTABLE_TERMINATING);
	val = scheme_make_pair(scheme_make_integer(kind), argv[i+2]);
      }

      ch = SCHEME_CHAR_VAL(argv[i]);
      if (!val) {
	scheme_hash_set(t->mapping, scheme_make_integer(ch), NULL);
	if (ch < 128)
	  t->fast_mapping[ch] = 0;
      } else {
	scheme_hash_set(t->mapping, scheme_make_integer(ch), val);
	if (ch < 128)
	  t->fast_mapping[ch] = (char)SCHEME_INT_VAL(SCHEME_CAR(val));
      }
    }
  }

  return (Scheme_Object *)t;
}

static Scheme_Object *readtable_mapping(int argc, Scheme_Object **argv)
{
  Scheme_Object *v1, *v2, *a[3];
  Readtable *t;
  int ch;

  if (!SAME_TYPE(scheme_readtable_type, SCHEME_TYPE(argv[0]))) {
    scheme_wrong_type("readtable-mapping", "readtable", 0, argc, argv);
    return NULL;
  }
  if (!SCHEME_CHARP(argv[1])) {
    scheme_wrong_type("readtable-mapping", "character", 1, argc, argv);
    return NULL;
  }
  
  t = (Readtable *)argv[0];
  ch = SCHEME_CHAR_VAL(argv[1]);
  
  v1 = scheme_hash_get(t->mapping, scheme_make_integer(ch));
  v2 = scheme_hash_get(t->mapping, scheme_make_integer(-ch));

  a[0] = argv[1];
  a[1] = scheme_false;
  if (v1) {
    int v;
    v = SCHEME_INT_VAL(SCHEME_CAR(v1));
    if (v & READTABLE_MAPPED) {
      v = SCHEME_INT_VAL(SCHEME_CDR(v1));
      a[0] = scheme_make_character(v);
      a[1] = scheme_false;
    } else if (v & READTABLE_CONTINUING) {
      a[0] = non_terminating_macro_symbol;
      a[1] = SCHEME_CDR(v1);
    } else if (v & READTABLE_TERMINATING) {
      a[0] = terminating_macro_symbol;
      a[1] = SCHEME_CDR(v1);
    }
  }
  a[2] = scheme_false;
  if (v2) {
    a[2] = v2;
  }

  return scheme_values(3, a);
}

static Scheme_Object *readtable_p(int argc, Scheme_Object **argv)
{
  return (SAME_TYPE(scheme_readtable_type, SCHEME_TYPE(argv[0]))
	  ? scheme_true
	  : scheme_false);
}

static Scheme_Object *readtable_or_false_p(int argc, Scheme_Object **argv)
{
  if (SCHEME_FALSEP(argv[0]))
    return scheme_true;
  return readtable_p(argc, argv);
}

static Scheme_Object *current_readtable(int argc, Scheme_Object **argv)
{
  return scheme_param_config("current-readtable", 
			     scheme_make_integer(MZCONFIG_READTABLE),
			     argc, argv,
			     -1, readtable_or_false_p, "readtable", 0);
}

static Scheme_Object *current_reader_guard(int argc, Scheme_Object **argv)
{
  return scheme_param_config("current-reader-guard", 
			     scheme_make_integer(MZCONFIG_READER_GUARD),
			     argc, argv,
			     1, NULL, NULL, 0);
}

static Scheme_Object *no_val_thunk(void *d, int argc, Scheme_Object **argv)
{
  return (Scheme_Object *)d;
}

static Scheme_Object *do_reader(Scheme_Object *modpath_stx,
                                Scheme_Object *port,
                                Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
                                int get_info,
                                Scheme_Hash_Table **ht,
                                Scheme_Object *indentation, ReadParams *params)
{
  Scheme_Object *modpath, *name, *a[3], *proc, *v, *no_val;
  int num_a;

  if (stxsrc)
    modpath = scheme_syntax_to_datum(modpath_stx, 0, NULL);
  else
    modpath = modpath_stx;

  proc = scheme_get_param(scheme_current_config(), MZCONFIG_READER_GUARD);

  a[0] = modpath;
  modpath = scheme_apply(proc, 1, a);
  
  a[0] = modpath;
  if (get_info)
    name = scheme_intern_symbol("get-info");
  else if (stxsrc)
    name = scheme_intern_symbol("read-syntax");
  else
    name = scheme_intern_symbol("read");
  a[1] = name;
  if (get_info) {
    no_val = scheme_make_pair(scheme_false, scheme_false);
    a[2] = scheme_make_closed_prim(no_val_thunk, no_val);
    num_a = 3;
  } else {
    no_val = NULL;
    num_a = 2;
  }

  proc = scheme_dynamic_require(num_a, a);
  if (get_info) {
    proc = scheme_force_value(proc);
  }

  if (get_info && SAME_OBJ(proc, no_val))
    return scheme_false;

  a[0] = proc;
  if (scheme_check_proc_arity(NULL, stxsrc ? 6 : 5, 0, 1, a)) {
    /* provide modpath_stx to reader */
  } else if (!get_info && scheme_check_proc_arity(NULL, stxsrc ? 2 : 1, 0, 1, a)) {
    /* don't provide modpath_stx to reader */
    modpath_stx = NULL;
  } else {
    scheme_wrong_type("#reader",
		      (stxsrc ? "procedure (arity 2 or 6)" 
                       : (get_info
                          ? "procedure (arity 5)"
                          : "procedure (arity 1 or 5)")),
		      -1, -1, a);
    return NULL;
  }

  v = readtable_call(0, 0, proc, params,
		     port, stxsrc, line, col, pos,
		     get_info, ht, modpath_stx);

  if (!get_info && scheme_special_comment_value(v))
    return NULL;
  else
    return v;
}

/* "#reader" has been read */
static Scheme_Object *read_reader(Scheme_Object *port,
				  Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
				  Scheme_Hash_Table **ht,
				  Scheme_Object *indentation, ReadParams *params)
{
  Scheme_Object *modpath;

  if (stxsrc)
    modpath = scheme_read_syntax(port, stxsrc);
  else
    modpath = scheme_read(port);

  if (SCHEME_EOFP(modpath)) {
    scheme_read_err(port, stxsrc, line, col, pos, 1, EOF, indentation, 
		    "read: expected a datum after #reader, found end-of-file");
    return NULL;
  }

  return do_reader(modpath, port, stxsrc, line, col, pos, 0, ht, indentation, params);
}

/* "#lang " has been read */
static Scheme_Object *read_lang(Scheme_Object *port,
                                Scheme_Object *stxsrc, intptr_t line, intptr_t col, intptr_t pos,
                                int get_info,
                                Scheme_Hash_Table **ht,
                                Scheme_Object *indentation, ReadParams *params,
                                int init_ch)
{
  int size, len;
  GC_CAN_IGNORE char *sfx;
  char *buf, *naya;
  int ch = 0;
  Scheme_Object *modpath;
  intptr_t name_line = -1, name_col = -1, name_pos = -1;

  size = 32;
  buf = MALLOC_N_ATOMIC(char, size);
  len = 0;

  if (init_ch) {
    ch = init_ch;
  } else {
    ch = scheme_getc_special_ok(port);
  }
  scheme_tell_all(port, &name_line, &name_col, &name_pos);

  while (1) {
    /* ch was only peeked at this point (except for the first iteration), so we
       can leave the input immediately after the language spec */
    if (ch == EOF) {
      break;
    } else if (ch == SCHEME_SPECIAL) {
      ch = scheme_getc_special_ok(port);
      scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation,
                      "read: found non-character while reading `#lang'");
    } else if (scheme_isspace(ch)) {
      break;
    } else {
      if (len) ch = scheme_getc_special_ok(port);
      if ((ch < 128)
          && (is_lang_nonsep_char(ch)
              || (ch == '/'))) {
        if (len + 1 >= size) {
          size *= 2;
          naya = MALLOC_N_ATOMIC(char, size);
          memcpy(naya, buf, len * sizeof(char));
          buf = naya;
        }
        buf[len++] = ch;
      } else {
        scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation, 
                        "read: expected only alphanumeric, `-', `+', `_', or `/'"
                        " characters for `#%s', found %c",
                        init_ch ? "!" : "lang",
                        ch);
        return NULL;
      }
    }
    ch = scheme_peekc_special_ok(port);
  }

  if (!len) {
    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation, 
                    (((ch == ' ') && !init_ch)
                     ? "read: expected a single space after `#lang'"
                     : "read: expected a non-empty sequence of alphanumeric, `-', `+', `_', or `/' after `#%s'"),
                    init_ch ? "!" : "lang ");
    return NULL;
  }
  if (buf[0] == '/') {
    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation, 
                    "read: expected a name that does not start `/' after `#lang'");
    return NULL;
  }
  if (buf[len - 1] == '/') {
    scheme_read_err(port, stxsrc, line, col, pos, SPAN(port, pos), ch, indentation, 
                    "read: expected a name that does not end `/' after `#%s'",
                    init_ch ? "!" : "lang");
    return NULL;
  }

  if (len + 16 >= size) {
    size += 16;
    naya = MALLOC_N_ATOMIC(char, size * sizeof(char));
    memcpy(naya, buf, len * sizeof(char));
    buf = naya;
  }
  sfx = "/lang/reader";
  while (*sfx) {
    buf[len++] = *(sfx++);
  }
  buf[len] = 0;

  modpath = scheme_intern_symbol(buf);
  if (stxsrc) {
    intptr_t span;
    span = SPAN(port, name_pos);
    modpath = scheme_make_stx_w_offset(modpath, name_line, name_col, name_pos, 
                                       span, 
                                       stxsrc, STX_SRCTAG);
  }

  return do_reader(modpath, port, stxsrc, line, col, pos, get_info, ht, indentation, params);
}

Scheme_Object *scheme_read_language(Scheme_Object *port, int nonlang_ok)
{
  return _internal_read(port, NULL, 0, 0, 0, 0, 0, -1,
                        NULL, NULL, NULL, NULL, nonlang_ok ? 2 : 1);
}

static Scheme_Object *expected_lang(const char *prefix, int ch,
                                    Scheme_Object *port, Scheme_Object *stxsrc,
                                    intptr_t line, intptr_t col, intptr_t pos,
                                    int get_lang)
{
  if (get_lang > 1) {
    return scheme_void;
  } else {
    mzchar chs[2];
    char *more;

    chs[0] = 0;
    chs[1] = 0;
      
    if (ch == EOF)
      more = "an end-of-file";
    else if (ch == SCHEME_SPECIAL)
      more = "a non-character";
    else {
      chs[0] = ch;
      more = "";
    }

    scheme_read_err(port, stxsrc, line, col, pos, 1, ch, NULL, 
                    "read-language: expected (after whitespace and comments)"
                    " `#lang ' or `#!' followed"
                    " immediately by a language name, found %s%s%5%s%s%s",
                    (*prefix || *chs) ? "`" : "", 
                    prefix, chs, 
                    (*prefix || *chs) ? "`" : "", 
                    ((*prefix || *chs) && *more) ? " followed by " : "", 
                    more);
    
    return NULL;
  }
}

/*========================================================================*/
/*                         precise GC traversers                          */
/*========================================================================*/

#ifdef MZ_PRECISE_GC

START_XFORM_SKIP;

#include "mzmark_read.inc"

static void register_traversers(void)
{
  GC_REG_TRAV(scheme_indent_type, mark_indent);
  GC_REG_TRAV(scheme_rt_compact_port, mark_cport);
  GC_REG_TRAV(scheme_readtable_type, mark_readtable);
  GC_REG_TRAV(scheme_rt_read_params, mark_read_params);
  GC_REG_TRAV(scheme_rt_delay_load_info, mark_delay_load);
  GC_REG_TRAV(scheme_rt_unmarshal_info, mark_unmarshal_tables);
}

END_XFORM_SKIP;

#endif
