guile/libguile/strings.c

/* Copyright (C) 1995,1996,1998,2000,2001, 2004, 2006, 2008 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 2.1 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
 */


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

#include <string.h>
#include <stdio.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"
#include "libguile/dynwind.h"



/* {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 wether 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.
 *
 * Stringbufs (and strings) are not stored very compactly: a stringbuf
 * has room for about 2*sizeof(scm_t_bits)-1 bytes additional
 * information.  As a compensation, the code below is made more
 * complicated by storing small strings inline in the double cell of a
 * stringbuf.  So we have fixstrings and bigstrings...
 */

#define STRINGBUF_F_SHARED      0x100
#define STRINGBUF_F_INLINE      0x200

#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_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_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_DEBUG
static size_t lenhist[1001];
#endif

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_DEBUG
  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);
    }
}

/* 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);
}


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)

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;
}

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);
  my_buf = make_stringbuf (len);
  memcpy (STRINGBUF_CHARS (my_buf),
	  STRINGBUF_CHARS (buf) + str_start + start, len);
  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);
}


/* Internal accessors
 */

size_t
scm_i_string_length (SCM str)
{
  return STRING_LENGTH (str);
}

const char *
scm_i_string_chars (SCM str)
{
  SCM buf;
  size_t start;
  get_str_buf_start (&str, &buf, &start);
  return STRINGBUF_CHARS (buf) + start;
}

char *
scm_i_string_writable_chars (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 stringbuf.  */

      size_t len = STRING_LENGTH (str);
      SCM new_buf;

      scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);

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

      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 STRINGBUF_CHARS (buf) + start;
}

void
scm_i_string_stop_writing (void)
{
  scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);
}

/* 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. */
      SCM new_buf = make_stringbuf (length);
      memcpy (STRINGBUF_CHARS (new_buf),
	      STRINGBUF_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));
}

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

const char *
scm_i_symbol_chars (SCM sym)
{
  SCM buf = SYMBOL_STRINGBUF (sym);
  return STRINGBUF_CHARS (buf);
}

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);
}

/* Debugging
 */

#if SCM_DEBUG

SCM scm_sys_string_dump (SCM);
SCM scm_sys_symbol_dump (SCM);
SCM scm_sys_stringbuf_hist (void);

SCM_DEFINE (scm_sys_string_dump, "%string-dump", 1, 0, 0,
	    (SCM str),
	    "")
#define FUNC_NAME s_scm_sys_string_dump
{
  SCM_VALIDATE_STRING (1, str);
  fprintf (stderr, "%p:\n", str);
  fprintf (stderr, " start: %u\n", STRING_START (str));
  fprintf (stderr, " len:   %u\n", STRING_LENGTH (str));
  if (IS_SH_STRING (str))
    {
      fprintf (stderr, " string: %p\n", SH_STRING_STRING (str));
      fprintf (stderr, "\n");
      scm_sys_string_dump (SH_STRING_STRING (str));
    }
  else
    {
      SCM buf = STRING_STRINGBUF (str);
      fprintf (stderr, " buf:   %p\n", buf);
      fprintf (stderr, "  chars:  %p\n", STRINGBUF_CHARS (buf));
      fprintf (stderr, "  length: %u\n", STRINGBUF_LENGTH (buf));
      fprintf (stderr, "  flags: %x\n", (SCM_CELL_WORD_0 (buf) & 0x300));
    }
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_sys_symbol_dump, "%symbol-dump", 1, 0, 0,
	    (SCM sym),
	    "")
#define FUNC_NAME s_scm_sys_symbol_dump
{
  SCM_VALIDATE_SYMBOL (1, sym);
  fprintf (stderr, "%p:\n", sym);
  fprintf (stderr, " hash: %lu\n", scm_i_symbol_hash (sym));
  {
    SCM buf = SYMBOL_STRINGBUF (sym);
    fprintf (stderr, " buf: %p\n", buf);
    fprintf (stderr, "  chars:  %p\n", STRINGBUF_CHARS (buf));
    fprintf (stderr, "  length: %u\n", STRINGBUF_LENGTH (buf));
    fprintf (stderr, "  shared: %u\n", STRINGBUF_SHARED (buf));
  }
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

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



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;
  size_t len;
  char *data;

  {
    long i = scm_ilength (chrs);

    SCM_ASSERT (i >= 0, chrs, SCM_ARG1, FUNC_NAME);
    len = i;
  }

  result = scm_i_make_string (len, &data);
  while (len > 0 && scm_is_pair (chrs))
    {
      SCM elt = SCM_CAR (chrs);

      SCM_VALIDATE_CHAR (SCM_ARGn, elt);
      *data++ = SCM_CHAR (elt);
      chrs = SCM_CDR (chrs);
      len--;
    }
  if (len > 0)
    scm_misc_error (NULL, "list changed while constructing string", SCM_EOL);
  if (!scm_is_null (chrs))
    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
{
  char *dst;
  SCM res = scm_i_make_string (len, &dst);

  if (!SCM_UNBNDP (chr))
    {
      SCM_VALIDATE_CHAR (0, chr);
      memset (dst, SCM_CHAR (chr), len);
    }

  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

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
{
  unsigned long idx;

  SCM_VALIDATE_STRING (1, str);
  idx = scm_to_unsigned_integer (k, 0, scm_i_string_length (str)-1);
  return SCM_MAKE_CHAR (scm_i_string_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));
  return SCM_MAKE_CHAR (scm_i_string_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
{
  unsigned long idx;

  SCM_VALIDATE_STRING (1, str);
  idx = scm_to_unsigned_integer (k, 0, scm_i_string_length(str)-1);
  SCM_VALIDATE_CHAR (3, chr);
  {
    char *dst = scm_i_string_writable_chars (str);
    dst[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));
  {
    char *dst = scm_i_string_writable_chars (str);
    dst[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 i = 0;
  SCM l, s;
  char *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);
      i += scm_i_string_length (s);
    }
  res = scm_i_make_string (i, &data);
  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);
      memcpy (data, scm_i_string_chars (s), len);
      data += 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);
  res = scm_i_make_string (len, &dst);
  memcpy (dst, str, len);
  return res;
}

SCM
scm_from_locale_string (const char *str)
{
  return scm_from_locale_stringn (str, -1);
}

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);
}

char *
scm_to_locale_stringn (SCM str, size_t *lenp)
{
  char *res;
  size_t len;

  if (!scm_is_string (str))
    scm_wrong_type_arg_msg (NULL, 0, str, "string");
  len = scm_i_string_length (str);
  res = scm_malloc (len + ((lenp==NULL)? 1 : 0));
  memcpy (res, scm_i_string_chars (str), len);
  if (lenp == NULL)
    {
      res[len] = '\0';
      if (strlen (res) != len)
	{
	  free (res);
	  scm_misc_error (NULL,
			  "string contains #\\nul character: ~S",
			  scm_list_1 (str));
	}
    }
  else
    *lenp = len;

  scm_remember_upto_here_1 (str);
  return res;
}

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;
  
  if (!scm_is_string (str))
    scm_wrong_type_arg_msg (NULL, 0, str, "string");
  len = scm_i_string_length (str);
  memcpy (buf, scm_i_string_chars (str), (len > max_len)? max_len : len);
  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)
{
  char **result;
  int len = scm_ilength (list);
  int i;

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

  scm_dynwind_begin (0);

  result = (char **) scm_malloc ((len + 1) * sizeof (char *));
  result[len] = NULL;
  scm_dynwind_unwind_handler (free, result, 0);

  /* 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++)
    {
      result[i] = scm_to_locale_string (SCM_CAR (list));
      list = SCM_CDR (list);
    }

  scm_dynwind_end ();
  return result;
}

void
scm_i_free_string_pointers (char **pointers)
{
  int i;
  
  for (i = 0; pointers[i]; i++)
    free (pointers[i]);
  free (pointers);
}

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 explicitely 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...
   */
  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:
*/