guile/libguile/print.c

/* Copyright 1995-2004,2006,2008-2019,2025
     Free Software Foundation, Inc.

   This file is part of Guile.

   Guile is free software: you can redistribute it and/or modify it
   under the terms of the GNU Lesser General Public License as published
   by the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   Guile 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 Lesser General Public
   License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with Guile.  If not, see
   <https://www.gnu.org/licenses/>.  */



#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <errno.h>
#include <stdio.h>
#include <assert.h>

#include <uniconv.h>
#include <unictype.h>

#include "alist.h"
#include "arrays-internal.h"
#include "atomic.h"
#include "bitvectors.h"
#include "bytevectors-internal.h"
#include "boolean.h"
#include "chars.h"
#include "continuations.h"
#include "control.h"
#include "ephemerons.h"
#include "eval.h"
#include "finalizers.h"
#include "fluids.h"
#include "foreign.h"
#include "frames.h"
#include "goops.h"
#include "gsubr.h"
#include "hashtab.h"
#include "keywords.h"
#include "macros.h"
#include "numbers.h"
#include "pairs.h"
#include "ports-internal.h"
#include "ports.h"
#include "private-options.h"
#include "procprop.h"
#include "programs.h"
#include "read.h"
#include "smob.h"
#include "srfi-14.h"
#include "strings.h"
#include "strports.h"
#include "struct.h"
#include "symbols.h"
#include "syntax.h"
#include "threads.h"
#include "values.h"
#include "variable.h"
#include "vectors.h"
#include "vm.h"

#include "print.h"




/* Character printers.  */

static void write_string (const void *, int, size_t, SCM);
static void write_character (scm_t_wchar, SCM);



/* {Names of immediate symbols}
 * 
 * This table must agree with the declarations in scm.h: {Immediate Symbols}.
 */

/* This table must agree with the list of flags in scm.h.  */
static const char *iflagnames[] =
{
  "#f",
  "#nil",  /* Elisp nil value. Should print from elisp as symbol `nil'. */
  "#<XXX UNUSED LISP FALSE -- DO NOT USE -- SHOULD NEVER BE SEEN XXX>",
  "()",
  "#t",
  "#<XXX UNUSED BOOLEAN 0 -- DO NOT USE -- SHOULD NEVER BE SEEN XXX>",
  "#<XXX UNUSED BOOLEAN 1 -- DO NOT USE -- SHOULD NEVER BE SEEN XXX>",
  "#<XXX UNUSED BOOLEAN 2 -- DO NOT USE -- SHOULD NEVER BE SEEN XXX>",
  "#<unspecified>",
  "#<undefined>",
  "#<eof>",

  /* Unbound slot marker for GOOPS.  For internal use in GOOPS only.  */
  "#<unbound>",
};

SCM_SYMBOL (sym_reader, "reader");

scm_t_option scm_print_opts[] = {
  { SCM_OPTION_SCM, "highlight-prefix", (scm_t_bits)SCM_BOOL_F_BITS,
    "The string to print before highlighted values." },
  { SCM_OPTION_SCM, "highlight-suffix", (scm_t_bits)SCM_BOOL_F_BITS,
    "The string to print after highlighted values." },
  { SCM_OPTION_SCM, "quote-keywordish-symbols", (scm_t_bits)SCM_BOOL_F_BITS,
    "How to print symbols that have a colon as their first or last character. "
    "The value '#f' does not quote the colons; '#t' quotes them; "
    "'reader' quotes them when the reader option 'keywords' is not '#f'." },
  { SCM_OPTION_BOOLEAN, "escape-newlines", 1,
    "Render newlines as \\n when printing using `write'." },
  { SCM_OPTION_BOOLEAN, "r7rs-symbols", 0,
    "Escape symbols using R7RS |...| symbol notation." },
  { 0 },
};

SCM_DEFINE (scm_print_options, "print-options-interface", 0, 1, 0, 
            (SCM setting),
	    "Option interface for the print options. Instead of using\n"
	    "this procedure directly, use the procedures\n"
	    "@code{print-enable}, @code{print-disable}, @code{print-set!}\n"
	    "and @code{print-options}.")
#define FUNC_NAME s_scm_print_options
{
  SCM ans = scm_options (setting,
			 scm_print_opts,
			 FUNC_NAME);
  return ans;
}
#undef FUNC_NAME


/* {Printing of Scheme Objects}
 */

/* Detection of circular references.
 *
 * Due to other constraints in the implementation, this code has bad
 * time complexity (O (depth * N)), The printer code can be
 * rewritten to be O(N).
 */
#define PUSH_REF(pstate, obj)			\
do						\
{						\
  PSTATE_STACK_SET (pstate, pstate->top, obj);	\
  pstate->top++;				\
  if (pstate->top == pstate->ceiling)		\
    grow_ref_stack (pstate);			\
} while(0)

#define ENTER_NESTED_DATA(pstate, obj, label)			\
do								\
{								\
  register unsigned long i;					\
  for (i = 0; i < pstate->top; ++i)				\
    if (scm_is_eq (PSTATE_STACK_REF (pstate, i), (obj)))	\
      goto label;						\
  if (pstate->fancyp)						\
    {								\
      if (pstate->top - pstate->list_offset >= pstate->level)	\
	{							\
	  scm_putc ('#', port);					\
	  return;						\
	}							\
    }								\
  PUSH_REF(pstate, obj);					\
} while(0)

#define EXIT_NESTED_DATA(pstate)				\
do								\
{								\
  --pstate->top;						\
  PSTATE_STACK_SET (pstate, pstate->top, SCM_UNDEFINED);	\
}								\
while (0)

SCM scm_print_state_vtable = SCM_BOOL_F;
static SCM print_state_pool = SCM_EOL;
scm_i_pthread_mutex_t print_state_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;

#ifdef GUILE_DEBUG /* Used for debugging purposes */

SCM_DEFINE (scm_current_pstate, "current-pstate", 0, 0, 0, 
           (),
	    "Return the current-pstate -- the car of the\n"
	    "@code{print_state_pool}.  @code{current-pstate} is only\n"
	    "included in @code{--enable-guile-debug} builds.")
#define FUNC_NAME s_scm_current_pstate
{
  if (!scm_is_null (print_state_pool))
    return SCM_CAR (print_state_pool);
  else
    return SCM_BOOL_F;
}
#undef FUNC_NAME

#endif

#define PSTATE_SIZE 50L

static SCM
make_print_state (void)
{
  SCM print_state = scm_make_struct_no_tail (scm_print_state_vtable, SCM_EOL);
  scm_print_state *pstate = SCM_PRINT_STATE (print_state);
  pstate->handle = print_state;
  pstate->ref_vect = scm_c_make_vector (PSTATE_SIZE, SCM_UNDEFINED);
  pstate->ceiling = SCM_SIMPLE_VECTOR_LENGTH (pstate->ref_vect);
  pstate->highlight_objects = SCM_EOL;
  return print_state;
}

SCM
scm_make_print_state ()
{
  SCM answer = SCM_BOOL_F;

  /* First try to allocate a print state from the pool */
  scm_i_pthread_mutex_lock (&print_state_mutex);
  if (!scm_is_null (print_state_pool))
    {
      answer = SCM_CAR (print_state_pool);
      print_state_pool = SCM_CDR (print_state_pool);
    }
  scm_i_pthread_mutex_unlock (&print_state_mutex);
  
  return scm_is_false (answer) ? make_print_state () : answer;
}

void
scm_free_print_state (SCM print_state)
{
  SCM handle;
  scm_print_state *pstate = SCM_PRINT_STATE (print_state);
  /* Cleanup before returning print state to pool.
   * It is better to do it here.  Doing it in scm_prin1
   * would cost more since that function is called much more
   * often.
   */
  pstate->fancyp = 0;
  pstate->revealed = 0;
  pstate->highlight_objects = SCM_EOL;
  scm_i_pthread_mutex_lock (&print_state_mutex);
  handle = scm_cons (print_state, print_state_pool);
  print_state_pool = handle;
  scm_i_pthread_mutex_unlock (&print_state_mutex);
}

SCM
scm_i_port_with_print_state (SCM port, SCM print_state)
{
  if (SCM_UNBNDP (print_state))
    {
      if (SCM_PORT_WITH_PS_P (port))
	return port;
      else
	print_state = scm_make_print_state ();
      /* port does not need to be coerced since it doesn't have ps */
    }
  else
    port = SCM_COERCE_OUTPORT (port);
  return scm_new_double_smob (scm_tc16_port_with_ps,
                              SCM_UNPACK (port), SCM_UNPACK (print_state), 0);
}

static void
grow_ref_stack (scm_print_state *pstate)
{
  SCM old_vect = pstate->ref_vect;
  size_t old_size = SCM_SIMPLE_VECTOR_LENGTH (old_vect);
  size_t new_size = 2 * pstate->ceiling;
  SCM new_vect = scm_c_make_vector (new_size, SCM_UNDEFINED);
  unsigned long int i;

  for (i = 0; i != old_size; ++i)
    SCM_SIMPLE_VECTOR_SET (new_vect, i, SCM_SIMPLE_VECTOR_REF (old_vect, i));

  pstate->ref_vect = new_vect;
  pstate->ceiling = new_size;
}

#define PSTATE_STACK_REF(p,i)   SCM_SIMPLE_VECTOR_REF((p)->ref_vect, (i))
#define PSTATE_STACK_SET(p,i,v) SCM_SIMPLE_VECTOR_SET((p)->ref_vect, (i), (v))

static void
print_circref (SCM port, scm_print_state *pstate, SCM ref)
{
  register long i;
  long self = pstate->top - 1;
  i = pstate->top - 1;
  if (scm_is_pair (PSTATE_STACK_REF (pstate, i)))
    {
      while (i > 0)
	{
	  if (!scm_is_pair (PSTATE_STACK_REF (pstate, i-1))
	      || !scm_is_eq (SCM_CDR (PSTATE_STACK_REF (pstate, i-1)), 
			     SCM_CDR (PSTATE_STACK_REF (pstate, i))))
	    break;
	  --i;
	}
      self = i;
    }
  for (i = pstate->top - 1; 1; --i)
    if (scm_is_eq (PSTATE_STACK_REF(pstate, i), ref))
      break;
  scm_putc ('#', port);
  scm_intprint (i - self, 10, port);
  scm_putc ('#', port);
}

/* Print the name of a symbol. */

static int
quote_keywordish_symbols (void)
{
  SCM option = SCM_PRINT_KEYWORD_STYLE;

  if (scm_is_false (option))
    return 0;
  if (scm_is_eq (option, sym_reader))
    return scm_is_true (SCM_PACK (SCM_KEYWORD_STYLE));
  return 1;
}

#define INITIAL_IDENTIFIER_MASK                                      \
  (UC_CATEGORY_MASK_Lu | UC_CATEGORY_MASK_Ll | UC_CATEGORY_MASK_Lt   \
   | UC_CATEGORY_MASK_Lm | UC_CATEGORY_MASK_Lo | UC_CATEGORY_MASK_Mn \
   | UC_CATEGORY_MASK_Nl | UC_CATEGORY_MASK_No | UC_CATEGORY_MASK_Pd \
   | UC_CATEGORY_MASK_Pc | UC_CATEGORY_MASK_Po | UC_CATEGORY_MASK_Sc \
   | UC_CATEGORY_MASK_Sm | UC_CATEGORY_MASK_Sk | UC_CATEGORY_MASK_So \
   | UC_CATEGORY_MASK_Co)

#define SUBSEQUENT_IDENTIFIER_MASK                                      \
  (INITIAL_IDENTIFIER_MASK                                              \
   | UC_CATEGORY_MASK_Nd | UC_CATEGORY_MASK_Mc | UC_CATEGORY_MASK_Me)

/* FIXME: Cache this information on the symbol, somehow.  */
static int
symbol_has_extended_read_syntax (SCM sym)
{
  size_t pos, len = scm_i_symbol_length (sym);
  scm_t_wchar c;

  /* The empty symbol.  */
  if (len == 0)
    return 1;

  c = scm_i_symbol_ref (sym, 0);

  switch (c) 
    {
    case '\'':
    case '`':
    case ',':
    case '"':
    case ';':
    case '#':
      /* Some initial-character constraints.  */
      return 1;

    case '|':
    case '\\':
      /* R7RS allows neither '|' nor '\' in bare symbols.  */
      if (SCM_PRINT_R7RS_SYMBOLS_P)
        return 1;
      break;
  
    case ':':
      /* Symbols that look like keywords.  */
      return quote_keywordish_symbols ();
  
    case '.':
      /* Single dot conflicts with dotted-pair notation.  */
      if (len == 1)
        return 1;
      /* Fall through to check numbers.  */
    case '+':
    case '-':
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6': 
    case '7':
    case '8':
    case '9':
     /* Number-ish symbols.  Numbers with radixes already caught be #
        above.  */
      if (scm_is_true (scm_i_string_to_number (scm_symbol_to_string (sym), 10)))
        return 1;
      break;

    default:
      break;
    }
  
  /* Other disallowed first characters.  */
  if (!uc_is_general_category_withtable (c, INITIAL_IDENTIFIER_MASK))
    return 1;

  /* Keywords can be identified by trailing colons too.  */
  if (scm_i_symbol_ref (sym, len - 1) == ':')
    return quote_keywordish_symbols ();

  /* Otherwise, any character that's in the identifier category mask is
     fine to pass through as-is, provided it's not one of the ASCII
     delimiters like `;'.  */
  for (pos = 1; pos < len; pos++)
    {
      c = scm_i_symbol_ref (sym, pos);
      if (!uc_is_general_category_withtable (c, SUBSEQUENT_IDENTIFIER_MASK))
        return 1;
      else if (c == '"' || c == ';' || c == '#')
        return 1;
      else if ((c == '|' || c == '\\') && SCM_PRINT_R7RS_SYMBOLS_P)
        /* R7RS allows neither '|' nor '\' in bare symbols.  */
        return 1;
    }

  return 0;
}

static void
print_normal_symbol (SCM sym, SCM port)
{
  size_t len = scm_i_symbol_length (sym);

  if (scm_i_is_narrow_symbol (sym))
    {
      const char *ptr = scm_i_symbol_chars (sym);
      scm_c_put_latin1_chars (port, (const uint8_t *) ptr, len);
    }
  else
    {
      const scm_t_wchar *ptr = scm_i_symbol_wide_chars (sym);
      scm_c_put_utf32_chars (port, (const uint32_t *) ptr, len);
    }
}

static void
print_extended_symbol (SCM sym, SCM port)
{
  size_t pos, len;

  len = scm_i_symbol_length (sym);
  scm_lfwrite ("#{", 2, port);

  for (pos = 0; pos < len; pos++)
    {
      scm_t_wchar c = scm_i_symbol_ref (sym, pos);
      
      if (uc_is_general_category_withtable (c,
                                            SUBSEQUENT_IDENTIFIER_MASK
                                            | UC_CATEGORY_MASK_Zs))
        scm_c_put_char (port, c);
      else
        {
          scm_lfwrite ("\\x", 2, port);
          scm_intprint (c, 16, port);
          scm_putc (';', port);
        }
    }

  scm_lfwrite ("}#", 2, port);
}

static void
print_r7rs_extended_symbol (SCM sym, SCM port)
{
  size_t pos, len;

  len = scm_i_symbol_length (sym);

  scm_putc ('|', port);

  for (pos = 0; pos < len; pos++)
    {
      scm_t_wchar c = scm_i_symbol_ref (sym, pos);

      switch (c)
        {
        case '\a': scm_lfwrite ("\\a", 2, port); break;
        case '\b': scm_lfwrite ("\\b", 2, port); break;
        case '\t': scm_lfwrite ("\\t", 2, port); break;
        case '\n': scm_lfwrite ("\\n", 2, port); break;
        case '\r': scm_lfwrite ("\\r", 2, port); break;
        case '|':  scm_lfwrite ("\\|", 2, port); break;
        case '\\': scm_lfwrite ("\\x5c;", 5, port); break;
        default:
          if (uc_is_general_category_withtable (c,
                                                UC_CATEGORY_MASK_L
                                                | UC_CATEGORY_MASK_M
                                                | UC_CATEGORY_MASK_N
                                                | UC_CATEGORY_MASK_P
                                                | UC_CATEGORY_MASK_S)
              || (c == ' '))
            scm_c_put_char (port, c);
          else
            {
              scm_lfwrite ("\\x", 2, port);
              scm_intprint (c, 16, port);
              scm_putc (';', port);
            }
          break;
        }
    }

  scm_putc ('|', port);
}

/* FIXME: allow R6RS hex escapes instead of #{...}# or |...|.  */
static void
print_symbol (SCM sym, SCM port)
{
  if (!symbol_has_extended_read_syntax (sym))
    print_normal_symbol (sym, port);
  else if (SCM_PRINT_R7RS_SYMBOLS_P)
    print_r7rs_extended_symbol (sym, port);
  else
    print_extended_symbol (sym, port);
}

void
scm_print_symbol_name (const char *str, size_t len, SCM port)
{
  SCM symbol = scm_from_utf8_symboln (str, len);
  print_symbol (symbol, port);
}

/* Print generally.  Handles both write and display according to PSTATE.
 */
SCM_GPROC(s_write, "write", 1, 1, 0, scm_write, g_write);
SCM_GPROC(s_display, "display", 1, 1, 0, scm_display, g_display);

static void iprin1 (SCM exp, SCM port, scm_print_state *pstate);


void 
scm_iprin1 (SCM exp, SCM port, scm_print_state *pstate)
{
  if (pstate->fancyp
      && scm_is_true (scm_memq (exp, pstate->highlight_objects)))
    {
      scm_display (SCM_PRINT_HIGHLIGHT_PREFIX, port);
      iprin1 (exp, port, pstate);
      scm_display (SCM_PRINT_HIGHLIGHT_SUFFIX, port);
    }
  else
    iprin1 (exp, port, pstate);
}

static void
print_vector (SCM v, size_t len, SCM (*ref) (SCM, size_t),
              SCM port, scm_print_state *pstate)
{
  long i;
  long last = len - 1;
  int cutp = 0;
  if (pstate->fancyp && len > pstate->length)
    {
      last = pstate->length - 1;
      cutp = 1;
    }
  for (i = 0; i < last; ++i)
    {
      scm_iprin1 (ref (v, i), port, pstate);
      scm_putc (' ', port);
    }
  if (i == last)
    {
      /* CHECK_INTS; */
      scm_iprin1 (ref (v, i), port, pstate);
    }
  if (cutp)
    scm_puts (" ...", port);
  scm_putc (')', port);
}

static void
iprin1 (SCM exp, SCM port, scm_print_state *pstate)
{
  switch (SCM_ITAG3 (exp))
    {
    case scm_tc3_tc7_1:
    case scm_tc3_tc7_2:
      /* These tc3 tags should never occur in an immediate value.  They are
       * only used in cell types of non-immediates, i. e. the value returned
       * by SCM_CELL_TYPE (exp) can use these tags.
       */
      scm_ipruk ("immediate", exp, port);
      break;
    case scm_tc3_int_1:
    case scm_tc3_int_2:
      scm_intprint (SCM_I_INUM (exp), 10, port);
      break;
    case scm_tc3_imm24:
      if (SCM_CHARP (exp))
	{
	  if (SCM_WRITINGP (pstate))
	    write_character (SCM_CHAR (exp), port);
	  else
            scm_c_put_char (port, SCM_CHAR (exp));
	}
      else if (SCM_IFLAGP (exp)
	       && ((size_t) SCM_IFLAGNUM (exp) < (sizeof iflagnames / sizeof (char *))))
        {
          scm_puts (iflagnames [SCM_IFLAGNUM (exp)], port);
        }
      else
	{
	  /* unknown immediate value */
	  scm_ipruk ("immediate", exp, port);
	}
      break;
    case scm_tc3_cons:
      switch (SCM_TYP7 (exp))
	{
	case scm_tcs_struct:
	  {
	    ENTER_NESTED_DATA (pstate, exp, circref);
	    if (SCM_OBJ_CLASS_FLAGS (exp) & SCM_CLASSF_GOOPS)
	      {
		SCM pwps, print = pstate->writingp ? g_write : g_display;
		if (SCM_UNPACK (print) == 0)
		  goto print_struct;
		pwps = scm_i_port_with_print_state (port, pstate->handle);
		pstate->revealed = 1;
		scm_call_2 (print, exp, pwps);
	      }
	    else
	      {
	      print_struct:
		scm_print_struct (exp, port, pstate);
	      }
	    EXIT_NESTED_DATA (pstate);
	  }
	  break;
	case scm_tcs_cons_imcar:
	case scm_tcs_cons_nimcar:
	  ENTER_NESTED_DATA (pstate, exp, circref);
	  scm_iprlist ("(", exp, ')', port, pstate);
	  EXIT_NESTED_DATA (pstate);
	  break;
	circref:
	  print_circref (port, pstate, exp);
	  break;
	case scm_tc7_number:
          switch SCM_TYP16 (exp) {
          case scm_tc16_big:
            scm_bigprint (exp, port, pstate);
            break;
          case scm_tc16_real:
            scm_print_real (exp, port, pstate);
            break;
          case scm_tc16_complex:
            scm_print_complex (exp, port, pstate);
            break;
          case scm_tc16_fraction:
            scm_i_print_fraction (exp, port, pstate);
            break;
          }
	  break;
        case scm_tc7_stringbuf:
          scm_i_print_stringbuf (exp, port, pstate);
          break;
        case scm_tc7_string:
	  {
	    size_t len = scm_i_string_length (exp);

	    if (SCM_WRITINGP (pstate))
              write_string (scm_i_string_data (exp),
                            scm_i_is_narrow_string (exp),
                            len, port);
	    else
              scm_c_put_string (port, exp, 0, len);
	  }
          scm_remember_upto_here_1 (exp);
          break;
	case scm_tc7_symbol:
	  if (scm_i_symbol_is_interned (exp))
	    {
	      print_symbol (exp, port);
	      scm_remember_upto_here_1 (exp);
	    }
	  else
	    {
	      scm_puts ("#<uninterned-symbol ", port);
	      print_symbol (exp, port);
	      scm_putc (' ', port);
	      scm_uintprint (SCM_UNPACK (exp), 16, port);
	      scm_putc ('>', port);
	    }
	  break;
	case scm_tc7_variable:
	  scm_i_variable_print (exp, port, pstate);
	  break;
        case scm_tc7_values:
          scm_puts ("#<values (", port);
          print_vector (exp, scm_values_count (scm_to_values (exp)),
                        scm_c_value_ref, port, pstate);
          scm_puts (">", port);
          break;
	case scm_tc7_program:
	  scm_i_program_print (exp, port, pstate);
	  break;
	case scm_tc7_pointer:
	  scm_i_pointer_print (exp, port, pstate);
	  break;
	case scm_tc7_hashtable:
	  scm_i_hashtable_print (exp, port, pstate);
	  break;
	case scm_tc7_fluid:
	  scm_i_fluid_print (exp, port, pstate);
	  break;
	case scm_tc7_dynamic_state:
	  scm_i_dynamic_state_print (exp, port, pstate);
	  break;
	case scm_tc7_frame:
	  scm_i_frame_print (exp, port, pstate);
	  break;
        case scm_tc7_keyword:
          scm_puts ("#:", port);
          scm_iprin1 (scm_keyword_to_symbol (exp), port, pstate);
          break;
        case scm_tc7_syntax:
	  scm_i_syntax_print (exp, port, pstate);
          break;
	case scm_tc7_atomic_box:
	  scm_i_atomic_box_print (exp, port, pstate);
	  break;
	case scm_tc7_vm_cont:
	  scm_i_vm_cont_print (exp, port, pstate);
	  break;
	case scm_tc7_array:
	  ENTER_NESTED_DATA (pstate, exp, circref);
          scm_i_print_array (exp, port, pstate);
          EXIT_NESTED_DATA (pstate);
          break;
	case scm_tc7_bytevector:
	  scm_i_print_bytevector (exp, port, pstate);
	  break;
	case scm_tc7_bitvector:
	  scm_i_print_bitvector (exp, port, pstate);
	  break;
	case scm_tc7_finalizer:
	  scm_i_print_finalizer (exp, port, pstate);
	  break;
	case scm_tc7_ephemeron:
	  scm_i_print_ephemeron (exp, port, pstate);
	  break;
	case scm_tc7_ephemeron_table:
	  scm_i_print_ephemeron_table (exp, port, pstate);
	  break;
	case scm_tc7_thread:
	  scm_i_print_thread (exp, port, pstate);
	  break;
	case scm_tc7_vector:
	  ENTER_NESTED_DATA (pstate, exp, circref);
	  scm_puts ("#(", port);
          print_vector (exp, SCM_SIMPLE_VECTOR_LENGTH (exp), scm_c_vector_ref,
                        port, pstate);
	  EXIT_NESTED_DATA (pstate);
	  break;
	case scm_tc7_port:
	  {
	    scm_t_port_type *ptob = SCM_PORT_TYPE (exp);
	    if (ptob->print && ptob->print (exp, port, pstate))
	      break;
	    goto punk;
	  }
	case scm_tc7_smob:
	  ENTER_NESTED_DATA (pstate, exp, circref);
	  SCM_SMOB_DESCRIPTOR (exp).print (exp, port, pstate);
	  EXIT_NESTED_DATA (pstate);
	  break;
	case scm_tc7_ext:
          switch (SCM_TYP16 (exp))
            {
              case scm_tc16_charset:
                scm_i_print_char_set (exp, port, pstate);
                break;
              default:
                abort ();
            }
          break;
	default:
          /* case scm_tcs_closures: */
	punk:
	  scm_ipruk ("type", exp, port);
	}
    }
}

/* Print states are necessary for circular reference safe printing.
 * They are also expensive to allocate.  Therefore print states are
 * kept in a pool so that they can be reused.
 */

/* The PORT argument can also be a print-state/port pair, which will
 * then be used instead of allocating a new print state.  This is
 * useful for continuing a chain of print calls from Scheme.  */

void 
scm_prin1 (SCM exp, SCM port, int writingp)
{
  SCM handle = SCM_BOOL_F; /* Will GC protect the handle whilst unlinked */
  SCM pstate_scm;
  scm_print_state *pstate;
  int old_writingp;

  /* If PORT is a print-state/port pair, use that.  Else create a new
     print-state. */

  if (SCM_PORT_WITH_PS_P (port))
    {
      pstate_scm = SCM_PORT_WITH_PS_PS (port);
      port = SCM_PORT_WITH_PS_PORT (port);
    }
  else
    {
      /* First try to allocate a print state from the pool */
      scm_i_pthread_mutex_lock (&print_state_mutex);
      if (!scm_is_null (print_state_pool))
	{
	  handle = print_state_pool;
	  print_state_pool = SCM_CDR (print_state_pool);
	}
      scm_i_pthread_mutex_unlock (&print_state_mutex);
      if (scm_is_false (handle))
	handle = scm_list_1 (make_print_state ());
      pstate_scm = SCM_CAR (handle);
    }

  pstate = SCM_PRINT_STATE (pstate_scm);
  old_writingp = pstate->writingp;
  pstate->writingp = writingp;
  scm_iprin1 (exp, port, pstate);
  pstate->writingp = old_writingp;

  /* Return print state to pool if it has been created above and
     hasn't escaped to Scheme. */

  if (scm_is_true (handle) && !pstate->revealed)
    {
      scm_i_pthread_mutex_lock (&print_state_mutex);
      SCM_SETCDR (handle, print_state_pool);
      print_state_pool = handle;
      scm_i_pthread_mutex_unlock (&print_state_mutex);
    }
}

static void
write_string (const void *str, int narrow_p, size_t len, SCM port)
{
  size_t i;

  scm_c_put_char (port, (uint8_t) '"');

  for (i = 0; i < len; ++i)
    {
      scm_t_wchar ch;
      if (narrow_p)
        ch = (scm_t_wchar) ((unsigned char *) (str))[i];
      else
        ch = ((scm_t_wchar *) (str))[i];

      /* Write CH to PORT, escaping it if it's non-graphic or not
         representable in PORT's encoding.  If CH needs to be escaped,
         it is escaped using the in-string escape syntax.  */
      if (ch == '"')
        scm_c_put_latin1_chars (port, (const uint8_t *) "\\\"", 2);
      else if (ch == '\\')
        scm_c_put_latin1_chars (port, (const uint8_t *) "\\\\", 2);
      else if (ch == '\n' && SCM_PRINT_ESCAPE_NEWLINES_P)
        scm_c_put_latin1_chars (port, (const uint8_t *) "\\n", 2);
      else if (ch == ' ' || ch == '\n'
               || (uc_is_general_category_withtable (ch,
                                                     UC_CATEGORY_MASK_L |
                                                     UC_CATEGORY_MASK_M |
                                                     UC_CATEGORY_MASK_N |
                                                     UC_CATEGORY_MASK_P |
                                                     UC_CATEGORY_MASK_S)
                   && scm_c_can_put_char (port, ch)))
        scm_c_put_char (port, ch);
      else
        scm_c_put_escaped_char (port, ch);
    }

  scm_c_put_char (port, (uint8_t) '"');
}

/* Write CH to PORT, escaping it if it's non-graphic or not
   representable in PORT's encoding.  The character escape syntax is
   used.  */
static void
write_character (scm_t_wchar ch, SCM port)
{
  scm_puts ("#\\", port);

  /* Pretty-print a combining characters over dotted circles, if
     possible, to make them more visible.  */
  if (uc_combining_class (ch) != UC_CCC_NR
      && scm_c_can_put_char (port, SCM_CODEPOINT_DOTTED_CIRCLE)
      && scm_c_can_put_char (port, ch))
    {
      scm_c_put_char (port, SCM_CODEPOINT_DOTTED_CIRCLE);
      scm_c_put_char (port, ch);
    }
  else if (uc_is_general_category_withtable (ch,
                                             UC_CATEGORY_MASK_L |
                                             UC_CATEGORY_MASK_M |
                                             UC_CATEGORY_MASK_N |
                                             UC_CATEGORY_MASK_P |
                                             UC_CATEGORY_MASK_S)
           && scm_c_can_put_char (port, ch))
    /* CH is graphic and encodeable; display it.  */
    scm_c_put_char (port, ch);
  else
    /* CH isn't graphic or cannot be represented in PORT's encoding.  */
    {
      /* Represent CH using the character escape syntax.  */
      const char *name;

      name = scm_i_charname (SCM_MAKE_CHAR (ch));
      if (name != NULL)
        scm_puts (name, port);
      else if (!SCM_R6RS_ESCAPES_P)
        scm_intprint (ch, 8, port);
      else
        {
          scm_puts ("x", port);
          scm_intprint (ch, 16, port);
        }
    }
}


/* Print an integer.
 */

void 
scm_intprint (intmax_t n, int radix, SCM port)
{
  char num_buf[SCM_INTBUFLEN];
  scm_lfwrite (num_buf, scm_iint2str (n, radix, num_buf), port);
}

void 
scm_uintprint (uintmax_t n, int radix, SCM port)
{
  char num_buf[SCM_INTBUFLEN];
  scm_lfwrite (num_buf, scm_iuint2str (n, radix, num_buf), port);
}

/* Print an object of unrecognized type.
 */

void 
scm_ipruk (char *hdr, SCM ptr, SCM port)
{
  scm_puts ("#<unknown-", port);
  scm_puts (hdr, port);
  if (1) /* (scm_in_heap_p (ptr)) */ /* FIXME */
    {
      scm_puts (" (0x", port);
      scm_uintprint (SCM_CELL_WORD_0 (ptr), 16, port);
      scm_puts (" . 0x", port);
      scm_uintprint (SCM_CELL_WORD_1 (ptr), 16, port);
      scm_puts (") @", port);
    }
  scm_puts (" 0x", port);
  scm_uintprint (SCM_UNPACK (ptr), 16, port);
  scm_putc ('>', port);
}


/* Print a list.
 */
void 
scm_iprlist (char *hdr, SCM exp, int tlr, SCM port, scm_print_state *pstate)
{
  register SCM hare, tortoise;
  long floor = pstate->top - 2;
  scm_puts (hdr, port);
  /* CHECK_INTS; */
  if (pstate->fancyp)
    goto fancy_printing;
  
  /* Run a hare and tortoise so that total time complexity will be
     O(depth * N) instead of O(N^2). */
  hare = SCM_CDR (exp);
  tortoise = exp;
  while (scm_is_pair (hare))
    {
      if (scm_is_eq (hare, tortoise))
	goto fancy_printing;
      hare = SCM_CDR (hare);
      if (!scm_is_pair (hare))
	break;
      hare = SCM_CDR (hare);
      tortoise = SCM_CDR (tortoise);
    }
  
  /* No cdr cycles intrinsic to this list */
  scm_iprin1 (SCM_CAR (exp), port, pstate);
  for (exp = SCM_CDR (exp); scm_is_pair (exp); exp = SCM_CDR (exp))
    {
      register long i;

      for (i = floor; i >= 0; --i)
	if (scm_is_eq (PSTATE_STACK_REF(pstate, i), exp))
	  goto circref;
      PUSH_REF (pstate, exp);
      scm_putc (' ', port);
      /* CHECK_INTS; */
      scm_iprin1 (SCM_CAR (exp), port, pstate);
    }
  if (!SCM_NULL_OR_NIL_P (exp))
    {
      scm_puts (" . ", port);
      scm_iprin1 (exp, port, pstate);
    }

end:
  scm_putc (tlr, port);
  pstate->top = floor + 2;
  return;
  
fancy_printing:
  {
    long n = pstate->length;
    
    scm_iprin1 (SCM_CAR (exp), port, pstate);
    exp = SCM_CDR (exp); --n;
    for (; scm_is_pair (exp); exp = SCM_CDR (exp))
      {
	register unsigned long i;

	for (i = 0; i < pstate->top; ++i)
	  if (scm_is_eq (PSTATE_STACK_REF(pstate, i), exp))
	    goto fancy_circref;
	if (pstate->fancyp)
	  {
	    if (n == 0)
	      {
		scm_puts (" ...", port);
		goto skip_tail;
	      }
	    else
	      --n;
	  }
	PUSH_REF(pstate, exp);
	++pstate->list_offset;
	scm_putc (' ', port);
	/* CHECK_INTS; */
	scm_iprin1 (SCM_CAR (exp), port, pstate);
      }
  }
  if (!SCM_NULL_OR_NIL_P (exp))
    {
      scm_puts (" . ", port);
      scm_iprin1 (exp, port, pstate);
    }
skip_tail:
  pstate->list_offset -= pstate->top - floor - 2;
  goto end;

fancy_circref:
  pstate->list_offset -= pstate->top - floor - 2;
  
circref:
  scm_puts (" . ", port);
  print_circref (port, pstate, exp);
  goto end;
}



int
scm_valid_oport_value_p	(SCM val)
{
  return (SCM_OPOUTPORTP (val)
          || (SCM_PORT_WITH_PS_P (val)
              && SCM_OPOUTPORTP (SCM_PORT_WITH_PS_PORT (val))));
}

/* SCM_GPROC(s_write, "write", 1, 1, 0, scm_write, g_write); */

SCM 
scm_write (SCM obj, SCM port)
{
  if (SCM_UNBNDP (port))
    port = scm_current_output_port ();

  SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG2, s_write);
  scm_prin1 (obj, port, 1);

  return SCM_UNSPECIFIED;
}


/* SCM_GPROC(s_display, "display", 1, 1, 0, scm_display, g_display); */

SCM 
scm_display (SCM obj, SCM port)
{
  if (SCM_UNBNDP (port))
    port = scm_current_output_port ();

  SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG2, s_display);
  scm_prin1 (obj, port, 0);

  return SCM_UNSPECIFIED;
}


SCM_DEFINE (scm_simple_format, "simple-format", 2, 0, 1,
            (SCM destination, SCM message, SCM args),
	    "Write @var{message} to @var{destination}, defaulting to\n"
	    "the current output port.\n"
	    "@var{message} can contain @code{~A} (was @code{%s}) and\n"
	    "@code{~S} (was @code{%S}) escapes.  When printed,\n"
	    "the escapes are replaced with corresponding members of\n"
	    "@var{args}:\n"
	    "@code{~A} formats using @code{display} and @code{~S} formats\n"
	    "using @code{write}.\n"
	    "If @var{destination} is @code{#t}, then use the current output\n"
	    "port, if @var{destination} is @code{#f}, then return a string\n"
	    "containing the formatted text. Does not add a trailing newline.")
#define FUNC_NAME s_scm_simple_format
{
  SCM port, answer = SCM_UNSPECIFIED;
  int fReturnString = 0;
  int writingp;
  size_t start, p, end;

  if (scm_is_eq (destination, SCM_BOOL_T))
    {
      destination = port = scm_current_output_port ();
      SCM_VALIDATE_OPORT_VALUE (1, destination);
    }
  else if (scm_is_false (destination))
    {
      fReturnString = 1;
      port = scm_mkstrport (SCM_INUM0, SCM_BOOL_F, SCM_WRTNG, FUNC_NAME);
      destination = port;
    }
  else
    {
      SCM_VALIDATE_OPORT_VALUE (1, destination);
      port = SCM_COERCE_OUTPORT (destination);
    }
  SCM_VALIDATE_STRING (2, message);
  SCM_VALIDATE_REST_ARGUMENT (args);

  p = 0;
  start = 0;
  end = scm_i_string_length (message);
  for (p = start; p != end; ++p)
    if (scm_i_string_ref (message, p) == '~')
      {
	if (++p == end)
	  break;

	switch (scm_i_string_ref (message, p)) 
	  {
	  case 'A': case 'a':
	    writingp = 0;
	    break;
	  case 'S': case 's':
	    writingp = 1;
	    break;
	  case '~':
	    scm_lfwrite_substr (message, start, p, port);
	    start = p + 1;
	    continue;
	  case '%':
	    scm_lfwrite_substr (message, start, p - 1, port);
	    scm_newline (port);
	    start = p + 1;
	    continue;
	  default:
	    SCM_MISC_ERROR ("FORMAT: Unsupported format option ~~~A - use (ice-9 format) instead",
			    scm_list_1 (scm_c_make_char (scm_i_string_ref (message, p))));
	    
	  }


	if (!scm_is_pair (args))
	  SCM_MISC_ERROR ("FORMAT: Missing argument for ~~~A",
			  scm_list_1 (scm_c_make_char (scm_i_string_ref (message, p))));
			  		
	scm_lfwrite_substr (message, start, p - 1, port);
	/* we pass destination here */
	scm_prin1 (SCM_CAR (args), destination, writingp);
	args = SCM_CDR (args);
	start = p + 1;
      }

  scm_lfwrite_substr (message, start, p, port);
  if (!scm_is_eq (args, SCM_EOL))
    SCM_MISC_ERROR ("FORMAT: ~A superfluous arguments",
		    scm_list_1 (scm_length (args)));

  if (fReturnString)
    answer = scm_strport_to_string (destination);

  return scm_return_first (answer, message);
}
#undef FUNC_NAME


SCM_DEFINE (scm_newline, "newline", 0, 1, 0, 
            (SCM port),
	    "Send a newline to @var{port}.\n"
	    "If @var{port} is omitted, send to the current output port.")
#define FUNC_NAME s_scm_newline
{
  if (SCM_UNBNDP (port))
    port = scm_current_output_port ();

  SCM_VALIDATE_OPORT_VALUE (1, port);

  scm_putc ('\n', SCM_COERCE_OUTPORT (port));
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_write_char, "write-char", 1, 1, 0,
            (SCM chr, SCM port),
	    "Send character @var{chr} to @var{port}.")
#define FUNC_NAME s_scm_write_char
{
  if (SCM_UNBNDP (port))
    port = scm_current_output_port ();
  else
    port = SCM_COERCE_OUTPORT (port);

  SCM_VALIDATE_CHAR (1, chr);
  SCM_VALIDATE_OPOUTPORT (2, port);

  scm_c_put_char (port, SCM_CHAR (chr));

  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME



/* Call back to Scheme code to do the printing of special objects
 * (like structs).  SCM_PRINTER_APPLY applies PROC to EXP and a smob
 * containing PORT and PSTATE.  This object can be used as the port for
 * display/write etc to continue the current print chain.  The REVEALED
 * field of PSTATE is set to true to indicate that the print state has
 * escaped to Scheme and thus has to be freed by the GC.
 */

scm_t_bits scm_tc16_port_with_ps;

/* Print exactly as the port itself would */

static int
port_with_ps_print (SCM obj, SCM port, scm_print_state *pstate)
{
  obj = SCM_PORT_WITH_PS_PORT (obj);
  return SCM_PORT_TYPE (obj)->print (obj, port, pstate);
}

SCM
scm_printer_apply (SCM proc, SCM exp, SCM port, scm_print_state *pstate)
{
  pstate->revealed = 1;
  return scm_call_2 (proc, exp,
		     scm_i_port_with_print_state (port, pstate->handle));
}

SCM_DEFINE (scm_port_with_print_state, "port-with-print-state", 1, 1, 0, 
            (SCM port, SCM pstate),
	    "Create a new port which behaves like @var{port}, but with an\n"
	    "included print state @var{pstate}.  @var{pstate} is optional.\n"
	    "If @var{pstate} isn't supplied and @var{port} already has\n"
	    "a print state, the old print state is reused.")
#define FUNC_NAME s_scm_port_with_print_state
{
  SCM_VALIDATE_OPORT_VALUE (1, port);
  if (!SCM_UNBNDP (pstate))
    SCM_VALIDATE_PRINTSTATE (2, pstate);
  return scm_i_port_with_print_state (port, pstate);
}
#undef FUNC_NAME

SCM_DEFINE (scm_get_print_state, "get-print-state", 1, 0, 0, 
            (SCM port),
	    "Return the print state of the port @var{port}. If @var{port}\n"
	    "has no associated print state, @code{#f} is returned.")
#define FUNC_NAME s_scm_get_print_state
{
  if (SCM_PORT_WITH_PS_P (port))
    return SCM_PORT_WITH_PS_PS (port);
  if (SCM_OUTPUT_PORT_P (port))
    return SCM_BOOL_F;
  SCM_WRONG_TYPE_ARG (1, port);
}
#undef FUNC_NAME



void
scm_init_print ()
{
  SCM type;

  type = scm_make_vtable (scm_from_utf8_string (SCM_PRINT_STATE_LAYOUT),
                          SCM_BOOL_F);
  scm_set_struct_vtable_name_x (type, scm_from_utf8_symbol ("print-state"));
  scm_print_state_vtable = type;

  /* Don't want to bind a wrapper class in GOOPS, so pass 0 as arg1. */
  scm_tc16_port_with_ps = scm_make_smob_type (0, 0);
  scm_set_smob_print (scm_tc16_port_with_ps, port_with_ps_print);

#include "print.x"

  scm_init_opts (scm_print_options, scm_print_opts);
  scm_print_opts[SCM_PRINT_HIGHLIGHT_PREFIX_I].val =
    SCM_UNPACK (scm_from_utf8_string ("{"));
  scm_print_opts[SCM_PRINT_HIGHLIGHT_SUFFIX_I].val =
    SCM_UNPACK (scm_from_utf8_string ("}"));
  scm_print_opts[SCM_PRINT_KEYWORD_STYLE_I].val = SCM_UNPACK (sym_reader);
}