[bpt/guile.git] / libguile / strings.c

/* Copyright (C) 1995,1996,1998,2000,2001, 2004, 2006, 2008, 2009 Free Software Foundation, Inc.
 * 
 * This library 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.
 *
 * 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser 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
 */


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

#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <unistr.h>
#include <uniconv.h>

#include "libguile/_scm.h"
#include "libguile/chars.h"
#include "libguile/root.h"
#include "libguile/strings.h"
#include "libguile/deprecation.h"
#include "libguile/validate.h"

\f

/* {Strings}
 */


/* Stringbufs 
 *
 * XXX - keeping an accurate refcount during GC seems to be quite
 * tricky, so we just keep score of whether a stringbuf might be
 * shared, not whether it definitely is.  
 *
 * The scheme I (mvo) tried to keep an accurate reference count would
 * recount all strings that point to a stringbuf during the mark-phase
 * of the GC.  This was done since one cannot access the stringbuf of
 * a string when that string is freed (in order to decrease the
 * reference count).  The memory of the stringbuf might have been
 * reused already for something completely different.
 *
 * This recounted worked for a small number of threads beating on
 * cow-strings, but it failed randomly with more than 10 threads, say.
 * I couldn't figure out what went wrong, so I used the conservative
 * approach implemented below.
 * 
 * A stringbuf needs to know its length, but only so that it can be
 * reported when the stringbuf is freed.
 *
 * There are 3 storage strategies for stringbufs: inline, outline, and
 * wide.
 *
 * Inline strings are small 8-bit strings stored within the double
 * cell itself.  Outline strings are larger 8-bit strings with GC
 * allocated storage.  Wide strings are 32-bit strings with allocated
 * storage.
 *
 * There was little value in making wide string inlineable, since
 * there is only room for three inlined 32-bit characters.  Thus wide
 * stringbufs are never inlined.
 */

#define STRINGBUF_F_SHARED      0x100
#define STRINGBUF_F_INLINE      0x200
#define STRINGBUF_F_WIDE        0x400 /* If true, strings have UCS-4
                                         encoding.  Otherwise, strings
                                         are Latin-1.  */

#define STRINGBUF_TAG           scm_tc7_stringbuf
#define STRINGBUF_SHARED(buf)   (SCM_CELL_WORD_0(buf) & STRINGBUF_F_SHARED)
#define STRINGBUF_INLINE(buf)   (SCM_CELL_WORD_0(buf) & STRINGBUF_F_INLINE)
#define STRINGBUF_WIDE(buf)     (SCM_CELL_WORD_0(buf) & STRINGBUF_F_WIDE)

#define STRINGBUF_OUTLINE_CHARS(buf)   ((char *)SCM_CELL_WORD_1(buf))
#define STRINGBUF_OUTLINE_LENGTH(buf)  (SCM_CELL_WORD_2(buf))
#define STRINGBUF_INLINE_CHARS(buf)    ((char *)SCM_CELL_OBJECT_LOC(buf,1))
#define STRINGBUF_INLINE_LENGTH(buf)   (((size_t)SCM_CELL_WORD_0(buf))>>16)

#define STRINGBUF_CHARS(buf)  (STRINGBUF_INLINE (buf) \
                               ? STRINGBUF_INLINE_CHARS (buf) \
                               : STRINGBUF_OUTLINE_CHARS (buf))

#define STRINGBUF_WIDE_CHARS(buf) ((scm_t_wchar *)SCM_CELL_WORD_1(buf))
#define STRINGBUF_LENGTH(buf) (STRINGBUF_INLINE (buf) \
                               ? STRINGBUF_INLINE_LENGTH (buf) \
                               : STRINGBUF_OUTLINE_LENGTH (buf))

#define STRINGBUF_MAX_INLINE_LEN (3*sizeof(scm_t_bits))

#define SET_STRINGBUF_SHARED(buf) \
  (SCM_SET_CELL_WORD_0 ((buf), SCM_CELL_WORD_0 (buf) | STRINGBUF_F_SHARED))

#if SCM_STRING_LENGTH_HISTOGRAM
static size_t lenhist[1001];
#endif

/* Make a stringbuf with space for LEN 8-bit Latin-1-encoded
   characters. */
static SCM
make_stringbuf (size_t len)
{
  /* XXX - for the benefit of SCM_STRING_CHARS, SCM_SYMBOL_CHARS and
     scm_i_symbol_chars, all stringbufs are null-terminated.  Once
     SCM_STRING_CHARS and SCM_SYMBOL_CHARS are removed and the code
     has been changed for scm_i_symbol_chars, this null-termination
     can be dropped.
  */

#if SCM_STRING_LENGTH_HISTOGRAM
  if (len < 1000)
    lenhist[len]++;
  else
    lenhist[1000]++;
#endif

  if (len <= STRINGBUF_MAX_INLINE_LEN-1)
    {
      return scm_double_cell (STRINGBUF_TAG | STRINGBUF_F_INLINE | (len << 16),
			      0, 0, 0);
    }
  else
    {
      char *mem = scm_gc_malloc_pointerless (len + 1, "string");
      mem[len] = '\0';
      return scm_double_cell (STRINGBUF_TAG, (scm_t_bits) mem,
			      (scm_t_bits) len, (scm_t_bits) 0);
    }
}

/* Make a stringbuf with space for LEN 32-bit UCS-4-encoded
   characters.  */
static SCM
make_wide_stringbuf (size_t len)
{
  scm_t_wchar *mem;
#if SCM_STRING_LENGTH_HISTOGRAM
  if (len < 1000)
    lenhist[len]++;
  else
    lenhist[1000]++;
#endif

  mem = scm_gc_malloc (sizeof (scm_t_wchar) * (len + 1), "string");
  mem[len] = 0;
  return scm_double_cell (STRINGBUF_TAG | STRINGBUF_F_WIDE, (scm_t_bits) mem,
                          (scm_t_bits) len, (scm_t_bits) 0);
}

/* Return a new stringbuf whose underlying storage consists of the LEN+1
   octets pointed to by STR (the last octet is zero).  */
SCM
scm_i_take_stringbufn (char *str, size_t len)
{
  scm_gc_register_collectable_memory (str, len + 1, "stringbuf");

  return scm_double_cell (STRINGBUF_TAG, (scm_t_bits) str,
			  (scm_t_bits) len, (scm_t_bits) 0);
}

/* Convert a stringbuf containing 8-bit Latin-1-encoded characters to
   one containing 32-bit UCS-4-encoded characters.  */
static void
widen_stringbuf (SCM buf)
{
  size_t i, len;
  scm_t_wchar *mem;

  if (STRINGBUF_WIDE (buf))
    return;

  if (STRINGBUF_INLINE (buf))
    {
      len = STRINGBUF_INLINE_LENGTH (buf);

      mem = scm_gc_malloc (sizeof (scm_t_wchar) * (len + 1), "string");
      for (i = 0; i < len; i++)
        mem[i] =
          (scm_t_wchar) (unsigned char) STRINGBUF_INLINE_CHARS (buf)[i];
      mem[len] = 0;

      SCM_SET_CELL_WORD_0 (buf, SCM_CELL_WORD_0 (buf) ^ STRINGBUF_F_INLINE);
      SCM_SET_CELL_WORD_0 (buf, SCM_CELL_WORD_0 (buf) | STRINGBUF_F_WIDE);
      SCM_SET_CELL_WORD_1 (buf, mem);
      SCM_SET_CELL_WORD_2 (buf, len);
    }
  else
    {
      len = STRINGBUF_OUTLINE_LENGTH (buf);

      mem = scm_gc_malloc (sizeof (scm_t_wchar) * (len + 1), "string");
      for (i = 0; i < len; i++)
        mem[i] =
          (scm_t_wchar) (unsigned char) STRINGBUF_OUTLINE_CHARS (buf)[i];
      mem[len] = 0;

      scm_gc_free (STRINGBUF_OUTLINE_CHARS (buf), len + 1, "string");

      SCM_SET_CELL_WORD_0 (buf, SCM_CELL_WORD_0 (buf) | STRINGBUF_F_WIDE);
      SCM_SET_CELL_WORD_1 (buf, mem);
      SCM_SET_CELL_WORD_2 (buf, len);
    }
}

scm_i_pthread_mutex_t stringbuf_write_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;

/* Copy-on-write strings.
 */

#define STRING_TAG            scm_tc7_string

#define STRING_STRINGBUF(str) (SCM_CELL_OBJECT_1(str))
#define STRING_START(str)     ((size_t)SCM_CELL_WORD_2(str))
#define STRING_LENGTH(str)    ((size_t)SCM_CELL_WORD_3(str))

#define SET_STRING_STRINGBUF(str,buf) (SCM_SET_CELL_OBJECT_1(str,buf))
#define SET_STRING_START(str,start) (SCM_SET_CELL_WORD_2(str,start))

#define IS_STRING(str)        (SCM_NIMP(str) && SCM_TYP7(str) == STRING_TAG)

/* Read-only strings.
 */

#define RO_STRING_TAG         (scm_tc7_string + 0x200)
#define IS_RO_STRING(str)     (SCM_CELL_TYPE(str)==RO_STRING_TAG)

/* Mutation-sharing substrings
 */

#define SH_STRING_TAG       (scm_tc7_string + 0x100)

#define SH_STRING_STRING(sh) (SCM_CELL_OBJECT_1(sh))
/* START and LENGTH as for STRINGs. */

#define IS_SH_STRING(str)   (SCM_CELL_TYPE(str)==SH_STRING_TAG)

/* Create a scheme string with space for LEN 8-bit Latin-1-encoded
   characters.  CHARSP, if not NULL, will be set to location of the
   char array.  */
SCM
scm_i_make_string (size_t len, char **charsp)
{
  SCM buf = make_stringbuf (len);
  SCM res;
  if (charsp)
    *charsp = STRINGBUF_CHARS (buf);
  res = scm_double_cell (STRING_TAG, SCM_UNPACK(buf),
			 (scm_t_bits)0, (scm_t_bits) len);
  return res;
}

/* Create a scheme string with space for LEN 32-bit UCS-4-encoded
   characters.  CHARSP, if not NULL, will be set to location of the
   character array.  */
SCM
scm_i_make_wide_string (size_t len, scm_t_wchar **charsp)
{
  SCM buf = make_wide_stringbuf (len);
  SCM res;
  if (charsp)
    *charsp = STRINGBUF_WIDE_CHARS (buf);
  res = scm_double_cell (STRING_TAG, SCM_UNPACK (buf),
                         (scm_t_bits) 0, (scm_t_bits) len);
  return res;
}

static void
validate_substring_args (SCM str, size_t start, size_t end)
{
  if (!IS_STRING (str))
    scm_wrong_type_arg_msg (NULL, 0, str, "string");
  if (start > STRING_LENGTH (str))
    scm_out_of_range (NULL, scm_from_size_t (start));
  if (end > STRING_LENGTH (str) || end < start)
    scm_out_of_range (NULL, scm_from_size_t (end));
}

static inline void
get_str_buf_start (SCM *str, SCM *buf, size_t *start)
{
  *start = STRING_START (*str);
  if (IS_SH_STRING (*str))
    {
      *str = SH_STRING_STRING (*str);
      *start += STRING_START (*str);
    }
  *buf = STRING_STRINGBUF (*str);
}

SCM
scm_i_substring (SCM str, size_t start, size_t end)
{
  SCM buf;
  size_t str_start;
  get_str_buf_start (&str, &buf, &str_start);
  scm_i_pthread_mutex_lock (&stringbuf_write_mutex);
  SET_STRINGBUF_SHARED (buf);
  scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);
  return scm_double_cell (STRING_TAG, SCM_UNPACK(buf),
			  (scm_t_bits)str_start + start,
			  (scm_t_bits) end - start);
}

SCM
scm_i_substring_read_only (SCM str, size_t start, size_t end)
{
  SCM buf;
  size_t str_start;
  get_str_buf_start (&str, &buf, &str_start);
  scm_i_pthread_mutex_lock (&stringbuf_write_mutex);
  SET_STRINGBUF_SHARED (buf);
  scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);
  return scm_double_cell (RO_STRING_TAG, SCM_UNPACK(buf),
			  (scm_t_bits)str_start + start,
			  (scm_t_bits) end - start);
}

SCM
scm_i_substring_copy (SCM str, size_t start, size_t end)
{
  size_t len = end - start;
  SCM buf, my_buf;
  size_t str_start;
  get_str_buf_start (&str, &buf, &str_start);
  if (scm_i_is_narrow_string (str))
    {
      my_buf = make_stringbuf (len);
      memcpy (STRINGBUF_CHARS (my_buf),
              STRINGBUF_CHARS (buf) + str_start + start, len);
    }
  else
    {
      my_buf = make_wide_stringbuf (len);
      u32_cpy ((scm_t_uint32 *) STRINGBUF_WIDE_CHARS (my_buf),
               (scm_t_uint32 *) (STRINGBUF_WIDE_CHARS (buf) + str_start 
                                 + start), len);
      /* Even though this string is wide, the substring may be narrow.
         Consider adding code to narrow the string.  */
    }
  scm_remember_upto_here_1 (buf);
  return scm_double_cell (STRING_TAG, SCM_UNPACK (my_buf),
                          (scm_t_bits) 0, (scm_t_bits) len);
}

SCM
scm_i_substring_shared (SCM str, size_t start, size_t end)
{
  if (start == 0 && end == STRING_LENGTH (str))
    return str;
  else 
    {
      size_t len = end - start;
      if (IS_SH_STRING (str))
	{
	  start += STRING_START (str);
	  str = SH_STRING_STRING (str);
	}
      return scm_double_cell (SH_STRING_TAG, SCM_UNPACK(str),
			      (scm_t_bits)start, (scm_t_bits) len);
    }
}

SCM
scm_c_substring (SCM str, size_t start, size_t end)
{
  validate_substring_args (str, start, end);
  return scm_i_substring (str, start, end);
}

SCM
scm_c_substring_read_only (SCM str, size_t start, size_t end)
{
  validate_substring_args (str, start, end);
  return scm_i_substring_read_only (str, start, end);
}

SCM
scm_c_substring_copy (SCM str, size_t start, size_t end)
{
  validate_substring_args (str, start, end);
  return scm_i_substring_copy (str, start, end);
}

SCM
scm_c_substring_shared (SCM str, size_t start, size_t end)
{
  validate_substring_args (str, start, end);
  return scm_i_substring_shared (str, start, end);
}

\f
/* Internal accessors
 */

/* Returns the number of characters in STR.  This may be different
   than the memory size of the string storage.  */
size_t
scm_i_string_length (SCM str)
{
  return STRING_LENGTH (str);
}

/* True if the string is 'narrow', meaning it has a 8-bit Latin-1
   encoding.  False if it is 'wide', having a 32-bit UCS-4
   encoding.  */
int
scm_i_is_narrow_string (SCM str)
{
  return !STRINGBUF_WIDE (STRING_STRINGBUF (str));
}

/* Returns a pointer to the 8-bit Latin-1 encoded character array of
   STR.  */
const char *
scm_i_string_chars (SCM str)
{
  SCM buf;
  size_t start;
  get_str_buf_start (&str, &buf, &start);
  if (scm_i_is_narrow_string (str))
    return STRINGBUF_CHARS (buf) + start;
  else
    scm_misc_error (NULL, "Invalid read access of chars of wide string: ~s",
                    scm_list_1 (str));
  return NULL;
}

/* Returns a pointer to the 32-bit UCS-4 encoded character array of
   STR.  */
const scm_t_wchar *
scm_i_string_wide_chars (SCM str)
{
  SCM buf;
  size_t start;

  get_str_buf_start (&str, &buf, &start);
  if (!scm_i_is_narrow_string (str))
    return STRINGBUF_WIDE_CHARS (buf) + start;
  else
    scm_misc_error (NULL, "Invalid read access of chars of narrow string: ~s",
                    scm_list_1 (str));
}

/* If the buffer in ORIG_STR is shared, copy ORIG_STR's characters to
   a new string buffer, so that it can be modified without modifying
   other strings.  Also, lock the string mutex.  Later, one must call
   scm_i_string_stop_writing to unlock the mutex.  */
SCM
scm_i_string_start_writing (SCM orig_str)
{
  SCM buf, str = orig_str;
  size_t start;

  get_str_buf_start (&str, &buf, &start);
  if (IS_RO_STRING (str))
    scm_misc_error (NULL, "string is read-only: ~s", scm_list_1 (orig_str));

  scm_i_pthread_mutex_lock (&stringbuf_write_mutex);
  if (STRINGBUF_SHARED (buf))
    {
      /* Clone the stringbuf.  */
      size_t len = STRING_LENGTH (str);
      SCM new_buf;

      scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);

      if (scm_i_is_narrow_string (str))
        {
          new_buf = make_stringbuf (len);
          memcpy (STRINGBUF_CHARS (new_buf),
                  STRINGBUF_CHARS (buf) + STRING_START (str), len);

        }
      else
        {
          new_buf = make_wide_stringbuf (len);
          u32_cpy ((scm_t_uint32 *) STRINGBUF_WIDE_CHARS (new_buf),
                   (scm_t_uint32 *) (STRINGBUF_WIDE_CHARS (buf) 
                                     + STRING_START (str)), len);
        }

      SET_STRING_STRINGBUF (str, new_buf);
      start -= STRING_START (str);

      /* FIXME: The following operations are not atomic, so other threads
	 looking at STR may see an inconsistent state.  Nevertheless it can't
	 hurt much since (i) accessing STR while it is being mutated can't
	 yield a crash, and (ii) concurrent accesses to STR should be
	 protected by a mutex at the application level.  The latter may not
	 apply when STR != ORIG_STR, though.  */
      SET_STRING_START (str, 0);
      SET_STRING_STRINGBUF (str, new_buf);

      buf = new_buf;

      scm_i_pthread_mutex_lock (&stringbuf_write_mutex);
    }
  return orig_str;
}

/* Return a pointer to the 8-bit Latin-1 chars of a string.  */
char *
scm_i_string_writable_chars (SCM str)
{
  SCM buf;
  size_t start;

  get_str_buf_start (&str, &buf, &start);
  if (scm_i_is_narrow_string (str))
    return STRINGBUF_CHARS (buf) + start;
  else
    scm_misc_error (NULL, "Invalid write access of chars of wide string: ~s",
                    scm_list_1 (str));
  return NULL;
}

/* Return a pointer to the UCS-4 codepoints of a string.  */
static scm_t_wchar *
scm_i_string_writable_wide_chars (SCM str)
{
  SCM buf;
  size_t start;

  get_str_buf_start (&str, &buf, &start);
  if (!scm_i_is_narrow_string (str))
    return STRINGBUF_WIDE_CHARS (buf) + start;
  else
    scm_misc_error (NULL, "Invalid read access of chars of narrow string: ~s",
                    scm_list_1 (str));
}

/* Unlock the string mutex that was locked when
   scm_i_string_start_writing was called.  */
void
scm_i_string_stop_writing (void)
{
  scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);
}

/* Return the Xth character of STR as a UCS-4 codepoint.  */
scm_t_wchar
scm_i_string_ref (SCM str, size_t x)
{
  if (scm_i_is_narrow_string (str))
    return (scm_t_wchar) (unsigned char) (scm_i_string_chars (str)[x]);
  else
    return scm_i_string_wide_chars (str)[x];
}

/* Set the Pth character of STR to UCS-4 codepoint CHR. */
void
scm_i_string_set_x (SCM str, size_t p, scm_t_wchar chr)
{
  if (chr > 0xFF && scm_i_is_narrow_string (str))
    widen_stringbuf (STRING_STRINGBUF (str));

  if (scm_i_is_narrow_string (str))
    {
      char *dst = scm_i_string_writable_chars (str);
      dst[p] = (char) (unsigned char) chr;
    }
  else
    {
      scm_t_wchar *dst = scm_i_string_writable_wide_chars (str);
      dst[p] = chr;
    }
}

/* Symbols.
 
   Basic symbol creation and accessing is done here, the rest is in
   symbols.[hc].  This has been done to keep stringbufs and the
   internals of strings and string-like objects confined to this file.
*/

#define SYMBOL_STRINGBUF SCM_CELL_OBJECT_1

SCM
scm_i_make_symbol (SCM name, scm_t_bits flags,
		   unsigned long hash, SCM props)
{
  SCM buf;
  size_t start = STRING_START (name);
  size_t length = STRING_LENGTH (name);

  if (IS_SH_STRING (name))
    {
      name = SH_STRING_STRING (name);
      start += STRING_START (name);
    }
  buf = SYMBOL_STRINGBUF (name);

  if (start == 0 && length == STRINGBUF_LENGTH (buf))
    {
      /* reuse buf. */
      scm_i_pthread_mutex_lock (&stringbuf_write_mutex);
      SET_STRINGBUF_SHARED (buf);
      scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);
    }
  else
    {
      /* make new buf. */
      if (scm_i_is_narrow_string (name))
        {
          SCM new_buf = make_stringbuf (length);
          memcpy (STRINGBUF_CHARS (new_buf),
                  STRINGBUF_CHARS (buf) + start, length);
          buf = new_buf;
        }
      else
        {
          SCM new_buf = make_wide_stringbuf (length);
          u32_cpy ((scm_t_uint32 *) STRINGBUF_WIDE_CHARS (new_buf),
                   (scm_t_uint32 *) STRINGBUF_WIDE_CHARS (buf) + start,
                   length);
          buf = new_buf;
        }
    }
  return scm_double_cell (scm_tc7_symbol | flags, SCM_UNPACK (buf),
			  (scm_t_bits) hash, SCM_UNPACK (props));
}

SCM
scm_i_c_make_symbol (const char *name, size_t len,
		     scm_t_bits flags, unsigned long hash, SCM props)
{
  SCM buf = make_stringbuf (len);
  memcpy (STRINGBUF_CHARS (buf), name, len);

  return scm_immutable_double_cell (scm_tc7_symbol | flags, SCM_UNPACK (buf),
				    (scm_t_bits) hash, SCM_UNPACK (props));
}

/* Return a new symbol that uses the LEN bytes pointed to by NAME as its
   underlying storage.  */
SCM
scm_i_c_take_symbol (char *name, size_t len,
		     scm_t_bits flags, unsigned long hash, SCM props)
{
  SCM buf = scm_i_take_stringbufn (name, len);

  return scm_double_cell (scm_tc7_symbol | flags, SCM_UNPACK (buf),
			  (scm_t_bits) hash, SCM_UNPACK (props));
}

/* Returns the number of characters in SYM.  This may be different
   from the memory size of SYM.  */
size_t
scm_i_symbol_length (SCM sym)
{
  return STRINGBUF_LENGTH (SYMBOL_STRINGBUF (sym));
}

size_t
scm_c_symbol_length (SCM sym)
#define FUNC_NAME "scm_c_symbol_length"
{
  SCM_VALIDATE_SYMBOL (1, sym);

  return STRINGBUF_LENGTH (SYMBOL_STRINGBUF (sym));
}
#undef FUNC_NAME

/* True if the name of SYM is stored as a Latin-1 encoded string.
   False if it is stored as a 32-bit UCS-4-encoded string.  */
int
scm_i_is_narrow_symbol (SCM sym)
{
  SCM buf;

  buf = SYMBOL_STRINGBUF (sym);
  return !STRINGBUF_WIDE (buf);
}

/* Returns a pointer to the 8-bit Latin-1 encoded character array that
   contains the name of SYM.  */
const char *
scm_i_symbol_chars (SCM sym)
{
  SCM buf;

  buf = SYMBOL_STRINGBUF (sym);
  if (!STRINGBUF_WIDE (buf))
    return STRINGBUF_CHARS (buf);
  else
    scm_misc_error (NULL, "Invalid access of chars of a wide symbol ~S",
                    scm_list_1 (sym));
}

/* Return a pointer to the 32-bit UCS-4-encoded character array of a
   symbol's name.  */
const scm_t_wchar *
scm_i_symbol_wide_chars (SCM sym)
{
  SCM buf;

  buf = SYMBOL_STRINGBUF (sym);
  if (STRINGBUF_WIDE (buf))
    return STRINGBUF_WIDE_CHARS (buf);
  else
    scm_misc_error (NULL, "Invalid access of chars of a narrow symbol ~S",
                    scm_list_1 (sym));
}

SCM
scm_i_symbol_substring (SCM sym, size_t start, size_t end)
{
  SCM buf = SYMBOL_STRINGBUF (sym);
  scm_i_pthread_mutex_lock (&stringbuf_write_mutex);
  SET_STRINGBUF_SHARED (buf);
  scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);
  return scm_double_cell (RO_STRING_TAG, SCM_UNPACK (buf),
			  (scm_t_bits)start, (scm_t_bits) end - start);
}

/* Returns the Xth character of symbol SYM as a UCS-4 codepoint.  */
scm_t_wchar
scm_i_symbol_ref (SCM sym, size_t x)
{
  if (scm_i_is_narrow_symbol (sym))
    return (scm_t_wchar) (unsigned char) (scm_i_symbol_chars (sym)[x]);
  else
    return scm_i_symbol_wide_chars (sym)[x];
}

/* Debugging
 */

SCM_DEFINE (scm_sys_string_dump, "%string-dump", 1, 0, 0, (SCM str), 
            "Returns an association list containing debugging information\n"
            "for @var{str}. The association list has the following entries."
            "@table @code\n"
            "@item string\n"
            "The string itself.\n"
            "@item start\n"
            "The start index of the string into its stringbuf\n"
            "@item length\n"
            "The length of the string\n"
            "@item shared\n"
            "If this string is a substring, it returns its parent string.\n"
            "Otherwise, it returns @code{#f}\n"
            "@item read-only\n"
            "@code{#t} if the string is read-only\n"
            "@item stringbuf-chars\n"
            "A new string containing this string's stringbuf's characters\n"
            "@item stringbuf-length\n"
            "The number of characters in this stringbuf\n"
            "@item stringbuf-shared\n"
            "@code{#t} if this stringbuf is shared\n"
            "@item stringbuf-inline\n"
            "@code{#t} if this stringbuf's characters are stored in the\n"
            "cell itself, or @code{#f} if they were allocated in memory\n"
            "@item stringbuf-wide\n"
            "@code{#t} if this stringbuf's characters are stored in a\n"
            "32-bit buffer, or @code{#f} if they are stored in an 8-bit\n"
            "buffer\n"
            "@end table")
#define FUNC_NAME s_scm_sys_string_dump
{
  SCM e1, e2, e3, e4, e5, e6, e7, e8, e9, e10;
  SCM buf;
  SCM_VALIDATE_STRING (1, str);

  /* String info */
  e1 = scm_cons (scm_from_locale_symbol ("string"),
                 str);
  e2 = scm_cons (scm_from_locale_symbol ("start"),
                 scm_from_size_t (STRING_START (str)));
  e3 = scm_cons (scm_from_locale_symbol ("length"),
                 scm_from_size_t (STRING_LENGTH (str)));

  if (IS_SH_STRING (str))
    {
      e4 = scm_cons (scm_from_locale_symbol ("shared"),
                     SH_STRING_STRING (str));
      buf = STRING_STRINGBUF (SH_STRING_STRING (str));
    }
  else
    {
      e4 = scm_cons (scm_from_locale_symbol ("shared"),
                     SCM_BOOL_F);
      buf = STRING_STRINGBUF (str);
    }

  if (IS_RO_STRING (str))
    e5 = scm_cons (scm_from_locale_symbol ("read-only"),
                   SCM_BOOL_T);
  else
    e5 = scm_cons (scm_from_locale_symbol ("read-only"),
                   SCM_BOOL_F);
      
  /* Stringbuf info */
  if (!STRINGBUF_WIDE (buf))
    {
      size_t len = STRINGBUF_LENGTH (buf);
      char *cbuf;
      SCM sbc = scm_i_make_string (len, &cbuf);
      memcpy (cbuf, STRINGBUF_CHARS (buf), len);
      e6 = scm_cons (scm_from_locale_symbol ("stringbuf-chars"),
                     sbc);
    }
  else
    {
      size_t len = STRINGBUF_LENGTH (buf);
      scm_t_wchar *cbuf;
      SCM sbc = scm_i_make_wide_string (len, &cbuf);
      u32_cpy ((scm_t_uint32 *) cbuf, 
               (scm_t_uint32 *) STRINGBUF_WIDE_CHARS (buf), len);
      e6 = scm_cons (scm_from_locale_symbol ("stringbuf-chars"),
                     sbc);
    }
  e7 = scm_cons (scm_from_locale_symbol ("stringbuf-length"), 
                 scm_from_size_t (STRINGBUF_LENGTH (buf)));
  if (STRINGBUF_SHARED (buf))
    e8 = scm_cons (scm_from_locale_symbol ("stringbuf-shared"), 
                   SCM_BOOL_T);
  else
    e8 = scm_cons (scm_from_locale_symbol ("stringbuf-shared"), 
                   SCM_BOOL_F);
  if (STRINGBUF_INLINE (buf))
    e9 = scm_cons (scm_from_locale_symbol ("stringbuf-inline"), 
                   SCM_BOOL_T);
  else
    e9 = scm_cons (scm_from_locale_symbol ("stringbuf-inline"), 
                   SCM_BOOL_F);
  if (STRINGBUF_WIDE (buf))
    e10 = scm_cons (scm_from_locale_symbol ("stringbuf-wide"),
                    SCM_BOOL_T);
  else
    e10 = scm_cons (scm_from_locale_symbol ("stringbuf-wide"),
                    SCM_BOOL_F);

  return scm_list_n (e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, SCM_UNDEFINED);
}
#undef FUNC_NAME

SCM_DEFINE (scm_sys_symbol_dump, "%symbol-dump", 1, 0, 0, (SCM sym),
            "Returns an association list containing debugging information\n"
            "for @var{sym}. The association list has the following entries."
            "@table @code\n"
            "@item symbol\n"
            "The symbol itself\n"
            "@item hash\n"
            "Its hash value\n"
            "@item interned\n"
            "@code{#t} if it is an interned symbol\n"
            "@item stringbuf-chars\n"
            "A new string containing this symbols's stringbuf's characters\n"
            "@item stringbuf-length\n"
            "The number of characters in this stringbuf\n"
            "@item stringbuf-shared\n"
            "@code{#t} if this stringbuf is shared\n"
            "@item stringbuf-inline\n"
            "@code{#t} if this stringbuf's characters are stored in the\n"
            "cell itself, or @code{#f} if they were allocated in memory\n"
            "@item stringbuf-wide\n"
            "@code{#t} if this stringbuf's characters are stored in a\n"
            "32-bit buffer, or @code{#f} if they are stored in an 8-bit\n"
            "buffer\n"
            "@end table")
#define FUNC_NAME s_scm_sys_symbol_dump
{
  SCM e1, e2, e3, e4, e5, e6, e7, e8;
  SCM buf;
  SCM_VALIDATE_SYMBOL (1, sym);
  e1 = scm_cons (scm_from_locale_symbol ("symbol"),
                 sym);
  e2 = scm_cons (scm_from_locale_symbol ("hash"),
                 scm_from_ulong (scm_i_symbol_hash (sym)));
  e3 = scm_cons (scm_from_locale_symbol ("interned"),
                 scm_symbol_interned_p (sym));
  buf = SYMBOL_STRINGBUF (sym);

  /* Stringbuf info */
  if (!STRINGBUF_WIDE (buf))
    {
      size_t len = STRINGBUF_LENGTH (buf);
      char *cbuf;
      SCM sbc = scm_i_make_string (len, &cbuf);
      memcpy (cbuf, STRINGBUF_CHARS (buf), len);
      e4 = scm_cons (scm_from_locale_symbol ("stringbuf-chars"),
                     sbc);
    }
  else
    {
      size_t len = STRINGBUF_LENGTH (buf);
      scm_t_wchar *cbuf;
      SCM sbc = scm_i_make_wide_string (len, &cbuf);
      u32_cpy ((scm_t_uint32 *) cbuf, 
               (scm_t_uint32 *) STRINGBUF_WIDE_CHARS (buf), len);
      e4 = scm_cons (scm_from_locale_symbol ("stringbuf-chars"),
                     sbc);
    }
  e5 = scm_cons (scm_from_locale_symbol ("stringbuf-length"), 
                 scm_from_size_t (STRINGBUF_LENGTH (buf)));
  if (STRINGBUF_SHARED (buf))
    e6 = scm_cons (scm_from_locale_symbol ("stringbuf-shared"), 
                   SCM_BOOL_T);
  else
    e6 = scm_cons (scm_from_locale_symbol ("stringbuf-shared"), 
                   SCM_BOOL_F);
  if (STRINGBUF_INLINE (buf))
    e7 = scm_cons (scm_from_locale_symbol ("stringbuf-inline"), 
                   SCM_BOOL_T);
  else
    e7 = scm_cons (scm_from_locale_symbol ("stringbuf-inline"), 
                   SCM_BOOL_F);
  if (STRINGBUF_WIDE (buf))
    e8 = scm_cons (scm_from_locale_symbol ("stringbuf-wide"),
                    SCM_BOOL_T);
  else
    e8 = scm_cons (scm_from_locale_symbol ("stringbuf-wide"),
                    SCM_BOOL_F);
  return scm_list_n (e1, e2, e3, e4, e5, e6, e7, e8, SCM_UNDEFINED);

}
#undef FUNC_NAME

#if SCM_STRING_LENGTH_HISTOGRAM

SCM_DEFINE (scm_sys_stringbuf_hist, "%stringbuf-hist", 0, 0, 0, (void), "")
#define FUNC_NAME s_scm_sys_stringbuf_hist
{
  int i;
  for (i = 0; i < 1000; i++)
    if (lenhist[i])
      fprintf (stderr, " %3d: %u\n", i, lenhist[i]);
  fprintf (stderr, ">999: %u\n", lenhist[1000]);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

#endif

\f

SCM_DEFINE (scm_string_p, "string?", 1, 0, 0, 
	    (SCM obj),
	    "Return @code{#t} if @var{obj} is a string, else @code{#f}.")
#define FUNC_NAME s_scm_string_p
{
  return scm_from_bool (IS_STRING (obj));
}
#undef FUNC_NAME


SCM_REGISTER_PROC (s_scm_list_to_string, "list->string", 1, 0, 0, scm_string);

SCM_DEFINE (scm_string, "string", 0, 0, 1, 
            (SCM chrs),
	    "@deffnx {Scheme Procedure} list->string chrs\n"
	    "Return a newly allocated string composed of the arguments,\n"
	    "@var{chrs}.")
#define FUNC_NAME s_scm_string
{
  SCM result;
  SCM rest;
  size_t len;
  size_t p = 0;
  long i;

  /* Verify that this is a list of chars.  */
  i = scm_ilength (chrs);
  SCM_ASSERT (i >= 0, chrs, SCM_ARG1, FUNC_NAME);

  len = (size_t) i;
  rest = chrs;

  while (len > 0 && scm_is_pair (rest))
    {
      SCM elt = SCM_CAR (rest);
      SCM_VALIDATE_CHAR (SCM_ARGn, elt);
      rest = SCM_CDR (rest);
      len--;
      scm_remember_upto_here_1 (elt);
    }

  /* Construct a string containing this list of chars.  */
  len = (size_t) i;
  rest = chrs;

  result = scm_i_make_string (len, NULL);
  result = scm_i_string_start_writing (result);
  while (len > 0 && scm_is_pair (rest))
    {
      SCM elt = SCM_CAR (rest);
      scm_i_string_set_x (result, p, SCM_CHAR (elt));
      p++;
      rest = SCM_CDR (rest);
      len--;
      scm_remember_upto_here_1 (elt);
    }
  scm_i_string_stop_writing ();

  if (len > 0)
    scm_misc_error (NULL, "list changed while constructing string", SCM_EOL);
  if (!scm_is_null (rest))
    scm_wrong_type_arg_msg (NULL, 0, chrs, "proper list");

  return result;
}
#undef FUNC_NAME

SCM_DEFINE (scm_make_string, "make-string", 1, 1, 0,
            (SCM k, SCM chr),
	    "Return a newly allocated string of\n"
            "length @var{k}.  If @var{chr} is given, then all elements of\n"
	    "the string are initialized to @var{chr}, otherwise the contents\n"
	    "of the @var{string} are unspecified.")
#define FUNC_NAME s_scm_make_string
{
  return scm_c_make_string (scm_to_size_t (k), chr);
}
#undef FUNC_NAME

SCM
scm_c_make_string (size_t len, SCM chr)
#define FUNC_NAME NULL
{
  size_t p;
  SCM res = scm_i_make_string (len, NULL);

  if (!SCM_UNBNDP (chr))
    {
      SCM_VALIDATE_CHAR (0, chr);
      res = scm_i_string_start_writing (res);
      for (p = 0; p < len; p++)
        scm_i_string_set_x (res, p, SCM_CHAR (chr));
      scm_i_string_stop_writing ();
    }

  return res;
}
#undef FUNC_NAME

SCM_DEFINE (scm_string_length, "string-length", 1, 0, 0, 
	    (SCM string),
	    "Return the number of characters in @var{string}.")
#define FUNC_NAME s_scm_string_length
{
  SCM_VALIDATE_STRING (1, string);
  return scm_from_size_t (STRING_LENGTH (string));
}
#undef FUNC_NAME

SCM_DEFINE (scm_string_width, "string-width", 1, 0, 0,
            (SCM string),
            "Return the bytes used to represent a character in @var{string}."
            "This will return 1 or 4.")
#define FUNC_NAME s_scm_string_width
{
  SCM_VALIDATE_STRING (1, string);
  if (!scm_i_is_narrow_string (string))
    return scm_from_int (4);

  return scm_from_int (1);
}
#undef FUNC_NAME

size_t
scm_c_string_length (SCM string)
{
  if (!IS_STRING (string))
    scm_wrong_type_arg_msg (NULL, 0, string, "string");
  return STRING_LENGTH (string);
}

SCM_DEFINE (scm_string_ref, "string-ref", 2, 0, 0,
            (SCM str, SCM k),
            "Return character @var{k} of @var{str} using zero-origin\n"
            "indexing. @var{k} must be a valid index of @var{str}.")
#define FUNC_NAME s_scm_string_ref
{
  size_t len;
  unsigned long idx;

  SCM_VALIDATE_STRING (1, str);

  len = scm_i_string_length (str);
  if (SCM_LIKELY (len > 0))
    idx = scm_to_unsigned_integer (k, 0, len - 1);
  else
    scm_out_of_range (NULL, k);

  if (scm_i_is_narrow_string (str))
    return SCM_MAKE_CHAR (scm_i_string_chars (str)[idx]);
  else
    return SCM_MAKE_CHAR (scm_i_string_wide_chars (str)[idx]);
}
#undef FUNC_NAME

SCM
scm_c_string_ref (SCM str, size_t p)
{
  if (p >= scm_i_string_length (str))
    scm_out_of_range (NULL, scm_from_size_t (p));
  if (scm_i_is_narrow_string (str))
    return SCM_MAKE_CHAR (scm_i_string_chars (str)[p]);
  else
    return SCM_MAKE_CHAR (scm_i_string_wide_chars (str)[p]);

}

SCM_DEFINE (scm_string_set_x, "string-set!", 3, 0, 0,
            (SCM str, SCM k, SCM chr),
            "Store @var{chr} in element @var{k} of @var{str} and return\n"
            "an unspecified value. @var{k} must be a valid index of\n"
            "@var{str}.")
#define FUNC_NAME s_scm_string_set_x
{
  size_t len;
  unsigned long idx;

  SCM_VALIDATE_STRING (1, str);

  len = scm_i_string_length (str);
  if (SCM_LIKELY (len > 0))
    idx = scm_to_unsigned_integer (k, 0, len - 1);
  else
    scm_out_of_range (NULL, k);

  SCM_VALIDATE_CHAR (3, chr);
  str = scm_i_string_start_writing (str);
  scm_i_string_set_x (str, idx, SCM_CHAR (chr));
  scm_i_string_stop_writing ();

  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

void
scm_c_string_set_x (SCM str, size_t p, SCM chr)
{
  if (p >= scm_i_string_length (str))
    scm_out_of_range (NULL, scm_from_size_t (p));
  str = scm_i_string_start_writing (str);
  scm_i_string_set_x (str, p, SCM_CHAR (chr));
  scm_i_string_stop_writing ();
}

SCM_DEFINE (scm_substring, "substring", 2, 1, 0,
	    (SCM str, SCM start, SCM end),
	    "Return a newly allocated string formed from the characters\n"
            "of @var{str} beginning with index @var{start} (inclusive) and\n"
	    "ending with index @var{end} (exclusive).\n"
            "@var{str} must be a string, @var{start} and @var{end} must be\n"
	    "exact integers satisfying:\n\n"
            "0 <= @var{start} <= @var{end} <= (string-length @var{str}).")
#define FUNC_NAME s_scm_substring
{
  size_t len, from, to;

  SCM_VALIDATE_STRING (1, str);
  len = scm_i_string_length (str);
  from = scm_to_unsigned_integer (start, 0, len);
  if (SCM_UNBNDP (end))
    to = len;
  else
    to = scm_to_unsigned_integer (end, from, len);
  return scm_i_substring (str, from, to);
}
#undef FUNC_NAME

SCM_DEFINE (scm_substring_read_only, "substring/read-only", 2, 1, 0,
	    (SCM str, SCM start, SCM end),
	    "Return a newly allocated string formed from the characters\n"
            "of @var{str} beginning with index @var{start} (inclusive) and\n"
	    "ending with index @var{end} (exclusive).\n"
            "@var{str} must be a string, @var{start} and @var{end} must be\n"
	    "exact integers satisfying:\n"
	    "\n"
            "0 <= @var{start} <= @var{end} <= (string-length @var{str}).\n"
	    "\n"
	    "The returned string is read-only.\n")
#define FUNC_NAME s_scm_substring_read_only
{
  size_t len, from, to;

  SCM_VALIDATE_STRING (1, str);
  len = scm_i_string_length (str);
  from = scm_to_unsigned_integer (start, 0, len);
  if (SCM_UNBNDP (end))
    to = len;
  else
    to = scm_to_unsigned_integer (end, from, len);
  return scm_i_substring_read_only (str, from, to);
}
#undef FUNC_NAME

SCM_DEFINE (scm_substring_copy, "substring/copy", 2, 1, 0,
	    (SCM str, SCM start, SCM end),
	    "Return a newly allocated string formed from the characters\n"
            "of @var{str} beginning with index @var{start} (inclusive) and\n"
	    "ending with index @var{end} (exclusive).\n"
            "@var{str} must be a string, @var{start} and @var{end} must be\n"
	    "exact integers satisfying:\n\n"
            "0 <= @var{start} <= @var{end} <= (string-length @var{str}).")
#define FUNC_NAME s_scm_substring_copy
{
  /* For the Scheme version, START is mandatory, but for the C
     version, it is optional.  See scm_string_copy in srfi-13.c for a
     rationale.
  */

  size_t from, to;

  SCM_VALIDATE_STRING (1, str);
  scm_i_get_substring_spec (scm_i_string_length (str),
			    start, &from, end, &to);
  return scm_i_substring_copy (str, from, to);
}
#undef FUNC_NAME

SCM_DEFINE (scm_substring_shared, "substring/shared", 2, 1, 0,
	    (SCM str, SCM start, SCM end),
	    "Return string that indirectly refers to the characters\n"
            "of @var{str} beginning with index @var{start} (inclusive) and\n"
	    "ending with index @var{end} (exclusive).\n"
            "@var{str} must be a string, @var{start} and @var{end} must be\n"
	    "exact integers satisfying:\n\n"
            "0 <= @var{start} <= @var{end} <= (string-length @var{str}).")
#define FUNC_NAME s_scm_substring_shared
{
  size_t len, from, to;

  SCM_VALIDATE_STRING (1, str);
  len = scm_i_string_length (str);
  from = scm_to_unsigned_integer (start, 0, len);
  if (SCM_UNBNDP (end))
    to = len;
  else
    to = scm_to_unsigned_integer (end, from, len);
  return scm_i_substring_shared (str, from, to);
}
#undef FUNC_NAME

SCM_DEFINE (scm_string_append, "string-append", 0, 0, 1, 
            (SCM args),
            "Return a newly allocated string whose characters form the\n"
            "concatenation of the given strings, @var{args}.")
#define FUNC_NAME s_scm_string_append
{
  SCM res;
  size_t len = 0;
  int wide = 0;
  SCM l, s;
  size_t i;
  union
  {
    char *narrow;
    scm_t_wchar *wide;
  } data;

  SCM_VALIDATE_REST_ARGUMENT (args);
  for (l = args; !scm_is_null (l); l = SCM_CDR (l))
    {
      s = SCM_CAR (l);
      SCM_VALIDATE_STRING (SCM_ARGn, s);
      len += scm_i_string_length (s);
      if (!scm_i_is_narrow_string (s))
        wide = 1;
    }
  data.narrow = NULL;
  if (!wide)
    res = scm_i_make_string (len, &data.narrow);
  else
    res = scm_i_make_wide_string (len, &data.wide);

  for (l = args; !scm_is_null (l); l = SCM_CDR (l))
    {
      size_t len;
      s = SCM_CAR (l);
      SCM_VALIDATE_STRING (SCM_ARGn, s);
      len = scm_i_string_length (s);
      if (!wide)
        {
          memcpy (data.narrow, scm_i_string_chars (s), len);
          data.narrow += len;
        }
      else
        {
          if (scm_i_is_narrow_string (s))
            {
              for (i = 0; i < scm_i_string_length (s); i++)
                data.wide[i] = (unsigned char) scm_i_string_chars (s)[i];
            }
          else
            u32_cpy ((scm_t_uint32 *) data.wide,
                     (scm_t_uint32 *) scm_i_string_wide_chars (s), len);
          data.wide += len;
        }
      scm_remember_upto_here_1 (s);
    }
  return res;
}
#undef FUNC_NAME

int
scm_is_string (SCM obj)
{
  return IS_STRING (obj);
}

SCM
scm_from_locale_stringn (const char *str, size_t len)
{
  SCM res;
  char *dst;

  if (len == (size_t) -1)
    len = strlen (str);
  if (len == 0)
    return scm_nullstr;

  res = scm_i_make_string (len, &dst);
  memcpy (dst, str, len);
  return res;
}

SCM
scm_from_locale_string (const char *str)
{
  if (str == NULL)
    return scm_nullstr;

  return scm_from_locale_stringn (str, -1);
}

/* Create a new scheme string from the C string STR.  The memory of
   STR may be used directly as storage for the new string.  */
SCM
scm_take_locale_stringn (char *str, size_t len)
{
  SCM buf, res;

  if (len == (size_t) -1)
    len = strlen (str);
  else
    {
      /* Ensure STR is null terminated.  A realloc for 1 extra byte should
         often be satisfied from the alignment padding after the block, with
         no actual data movement.  */
      str = scm_realloc (str, len + 1);
      str[len] = '\0';
    }

  buf = scm_i_take_stringbufn (str, len);
  res = scm_double_cell (STRING_TAG,
                         SCM_UNPACK (buf), (scm_t_bits) 0, (scm_t_bits) len);
  return res;
}

SCM
scm_take_locale_string (char *str)
{
  return scm_take_locale_stringn (str, -1);
}

/* Change libunistring escapes (\uXXXX and \UXXXXXXXX) to \xXX \uXXXX
   and \UXXXXXX.  */
static void
unistring_escapes_to_guile_escapes (char **bufp, size_t *lenp)
{
  char *before, *after;
  size_t i, j;

  before = *bufp;
  after = *bufp;
  i = 0;
  j = 0;
  while (i < *lenp)
    {
      if ((i <= *lenp - 6)
          && before[i] == '\\'
          && before[i + 1] == 'u'
          && before[i + 2] == '0' && before[i + 3] == '0')
        {
          /* Convert \u00NN to \xNN */
          after[j] = '\\';
          after[j + 1] = 'x';
          after[j + 2] = tolower ((int) before[i + 4]);
          after[j + 3] = tolower ((int) before[i + 5]);
          i += 6;
          j += 4;
        }
      else if ((i <= *lenp - 10)
               && before[i] == '\\'
               && before[i + 1] == 'U'
               && before[i + 2] == '0' && before[i + 3] == '0')
        {
          /* Convert \U00NNNNNN to \UNNNNNN */
          after[j] = '\\';
          after[j + 1] = 'U';
          after[j + 2] = tolower ((int) before[i + 4]);
          after[j + 3] = tolower ((int) before[i + 5]);
          after[j + 4] = tolower ((int) before[i + 6]);
          after[j + 5] = tolower ((int) before[i + 7]);
          after[j + 6] = tolower ((int) before[i + 8]);
          after[j + 7] = tolower ((int) before[i + 9]);
          i += 10;
          j += 8;
        }
      else
        {
          after[j] = before[i];
          i++;
          j++;
        }
    }
  *lenp = j;
  after = scm_realloc (after, j);
}

char *
scm_to_locale_stringn (SCM str, size_t * lenp)
{
  const char *enc;

  /* In the future, enc will hold the port's encoding.  */
  enc = NULL;

  return scm_to_stringn (str, lenp, enc, 
                         SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE);
}

/* Low-level scheme to C string conversion function.  */
char *
scm_to_stringn (SCM str, size_t * lenp, const char *encoding,
                scm_t_string_failed_conversion_handler handler)
{
  static const char iso[11] = "ISO-8859-1";
  char *buf;
  size_t ilen, len, i;

  if (!scm_is_string (str))
    scm_wrong_type_arg_msg (NULL, 0, str, "string");
  ilen = scm_i_string_length (str);

  if (ilen == 0)
    {
      buf = scm_malloc (1);
      buf[0] = '\0';
      if (lenp)
        *lenp = 0;
      return buf;
    }
	
  if (lenp == NULL)
    for (i = 0; i < ilen; i++)
      if (scm_i_string_ref (str, i) == '\0')
        scm_misc_error (NULL,
                        "string contains #\\nul character: ~S",
                        scm_list_1 (str));

  if (scm_i_is_narrow_string (str))
    {
      if (lenp)
        {
          buf = scm_malloc (ilen);
          memcpy (buf, scm_i_string_chars (str), ilen);
          *lenp = ilen;
          return buf;
        }
      else
        {
          buf = scm_malloc (ilen + 1);
          memcpy (buf, scm_i_string_chars (str), ilen);
          buf[ilen] = '\0';
          return buf;
        }
    }

  
  buf = NULL;
  len = 0;
  buf = u32_conv_to_encoding (iso,
                              (enum iconv_ilseq_handler) handler,
                              (scm_t_uint32 *) scm_i_string_wide_chars (str),
                              ilen, NULL, NULL, &len);
  if (buf == NULL)
    scm_misc_error (NULL, "cannot convert to output locale ~s: \"~s\"",
                    scm_list_2 (scm_from_locale_string (iso), str));

  if (handler == SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE)
    unistring_escapes_to_guile_escapes (&buf, &len);

  if (lenp)
    *lenp = len;
  else
    {
      buf = scm_realloc (buf, len + 1);
      buf[len] = '\0';
    }

  scm_remember_upto_here_1 (str);
  return buf;
}

char *
scm_to_locale_string (SCM str)
{
  return scm_to_locale_stringn (str, NULL);
}

size_t
scm_to_locale_stringbuf (SCM str, char *buf, size_t max_len)
{
  size_t len;
  char *result = NULL;
  if (!scm_is_string (str))
    scm_wrong_type_arg_msg (NULL, 0, str, "string");
  result = scm_to_locale_stringn (str, &len);

  memcpy (buf, result, (len > max_len) ? max_len : len);
  free (result);

  scm_remember_upto_here_1 (str);
  return len;
}

/* converts C scm_array of strings to SCM scm_list of strings. */
/* If argc < 0, a null terminated scm_array is assumed. */
SCM
scm_makfromstrs (int argc, char **argv)
{
  int i = argc;
  SCM lst = SCM_EOL;
  if (0 > i)
    for (i = 0; argv[i]; i++);
  while (i--)
    lst = scm_cons (scm_from_locale_string (argv[i]), lst);
  return lst;
}

/* Return a newly allocated array of char pointers to each of the strings
   in args, with a terminating NULL pointer.  */

char **
scm_i_allocate_string_pointers (SCM list)
#define FUNC_NAME "scm_i_allocate_string_pointers"
{
  char **result;
  int len = scm_ilength (list);
  int i;

  if (len < 0)
    scm_wrong_type_arg_msg (NULL, 0, list, "proper list");

  result = scm_gc_malloc ((len + 1) * sizeof (char *),
			  "string pointers");
  result[len] = NULL;

  /* The list might be have been modified in another thread, so
     we check LIST before each access.
   */
  for (i = 0; i < len && scm_is_pair (list); i++)
    {
      SCM str;
      size_t len;

      str = SCM_CAR (list);
      len = scm_c_string_length (str);

      result[i] = scm_gc_malloc_pointerless (len + 1, "string pointers");
      memcpy (result[i], scm_i_string_chars (str), len);
      result[i][len] = '\0';

      list = SCM_CDR (list);
    }

  return result;
}
#undef FUNC_NAME

void
scm_i_get_substring_spec (size_t len,
			  SCM start, size_t *cstart,
			  SCM end, size_t *cend)
{
  if (SCM_UNBNDP (start))
    *cstart = 0;
  else
    *cstart = scm_to_unsigned_integer (start, 0, len);

  if (SCM_UNBNDP (end))
    *cend = len;
  else
    *cend = scm_to_unsigned_integer (end, *cstart, len);
}
		  
#if SCM_ENABLE_DEPRECATED

/* When these definitions are removed, it becomes reasonable to use
   read-only strings for string literals.  For that, change the reader
   to create string literals with scm_c_substring_read_only instead of
   with scm_c_substring_copy.
*/

int
scm_i_deprecated_stringp (SCM str)
{
  scm_c_issue_deprecation_warning
    ("SCM_STRINGP is deprecated.  Use scm_is_string instead.");
  
  return scm_is_string (str);
}

char *
scm_i_deprecated_string_chars (SCM str)
{
  char *chars;

  scm_c_issue_deprecation_warning
    ("SCM_STRING_CHARS is deprecated.  See the manual for alternatives.");

  /* We don't accept shared substrings here since they are not
     null-terminated.
  */
  if (IS_SH_STRING (str))
    scm_misc_error (NULL, 
		    "SCM_STRING_CHARS does not work with shared substrings.",
		    SCM_EOL);

  /* We explicitly test for read-only strings to produce a better
     error message.
  */

  if (IS_RO_STRING (str))
    scm_misc_error (NULL, 
		    "SCM_STRING_CHARS does not work with read-only strings.",
		    SCM_EOL);
    
  /* The following is still wrong, of course...
   */
  str = scm_i_string_start_writing (str);
  chars = scm_i_string_writable_chars (str);
  scm_i_string_stop_writing ();
  return chars;
}

size_t
scm_i_deprecated_string_length (SCM str)
{
  scm_c_issue_deprecation_warning
    ("SCM_STRING_LENGTH is deprecated.  Use scm_c_string_length instead.");
  return scm_c_string_length (str);
}

#endif

void
scm_init_strings ()
{
  scm_nullstr = scm_i_make_string (0, NULL);

#include "libguile/strings.x"
}


/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/