/* searchutils.c - helper subroutines for grep's matchers.
   Copyright 1992, 1998, 2000, 2007, 2009-2012 Free Software Foundation, Inc.

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

   This program 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 General Public License for more details.

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

#include <config.h>
#include <assert.h>
#include "search.h"

#define NCHAR (UCHAR_MAX + 1)

void
kwsinit (kwset_t *kwset)
{
  static char trans[NCHAR];
  int i;

  if (match_icase && MB_CUR_MAX == 1)
    {
      for (i = 0; i < NCHAR; ++i)
        trans[i] = tolower (i);

      *kwset = kwsalloc (trans);
    }
  else
    *kwset = kwsalloc (NULL);

  if (!*kwset)
    xalloc_die ();
}

#if MBS_SUPPORT
/* Convert the *N-byte string, BEG, to lower-case, and write the
   NUL-terminated result into malloc'd storage.  Upon success, set *N
   to the length (in bytes) of the resulting string (not including the
   trailing NUL byte), and return a pointer to the lower-case string.
   Upon memory allocation failure, this function exits.
   Note that on input, *N must be larger than zero.

   Note that while this function returns a pointer to malloc'd storage,
   the caller must not free it, since this function retains a pointer
   to the buffer and reuses it on any subsequent call.  As a consequence,
   this function is not thread-safe.

   When each character in the lower-case result string has the same length
   as the corresponding character in the input string, set *LEN_MAP_P
   to NULL.  Otherwise, set it to a malloc'd buffer (like the returned
   buffer, this must not be freed by caller) of the same length as the
   result string.  (*LEN_MAP_P)[J] is the change in byte-length of the
   character in BEG that formed byte J of the result as it was converted to
   lower-case.  It is usually zero.  For the upper-case Turkish I-with-dot
   it is -1, since the upper-case character occupies two bytes, while the
   lower-case one occupies only one byte.  For the Turkish-I-without-dot
   in the tr_TR.utf8 locale, it is 1 because the lower-case representation
   is one byte longer than the original.  When that happens, we have two
   or more slots in *LEN_MAP_P for each such character.  We store the
   difference in the first one and 0's in any remaining slots.

   This map is used by the caller to convert offset,length pairs that
   reference the lower-case result to numbers that refer to the matched
   part of the original buffer.  */

char *
mbtolower (const char *beg, size_t *n, mb_len_map_t **len_map_p)
{
  static char *out;
  static mb_len_map_t *len_map;
  static size_t outalloc;
  size_t outlen, mb_cur_max;
  mbstate_t is, os;
  const char *end;
  char *p;
  mb_len_map_t *m;
  bool lengths_differ = false;

  if (*n > outalloc || outalloc == 0)
    {
      outalloc = MAX(1, *n);
      out = xrealloc (out, outalloc);
      len_map = xrealloc (len_map, outalloc);
    }

  /* appease clang-2.6 */
  assert (out);
  assert (len_map);
  if (*n == 0)
    return out;

  memset (&is, 0, sizeof (is));
  memset (&os, 0, sizeof (os));
  end = beg + *n;

  mb_cur_max = MB_CUR_MAX;
  p = out;
  m = len_map;
  outlen = 0;
  while (beg < end)
    {
      wchar_t wc;
      size_t mbclen = mbrtowc (&wc, beg, end - beg, &is);
      if (outlen + mb_cur_max >= outalloc)
        {
          size_t dm = m - len_map;
          out = x2nrealloc (out, &outalloc, 1);
          len_map = xrealloc (len_map, outalloc);
          p = out + outlen;
          m = len_map + dm;
        }

      if (mbclen == (size_t) -1 || mbclen == (size_t) -2 || mbclen == 0)
        {
          /* An invalid sequence, or a truncated multi-octet character.
             We treat it as a single-octet character.  */
          *m++ = 0;
          *p++ = *beg++;
          outlen++;
          memset (&is, 0, sizeof (is));
          memset (&os, 0, sizeof (os));
        }
      else
        {
          beg += mbclen;
          size_t ombclen = wcrtomb (p, towlower ((wint_t) wc), &os);
          *m = mbclen - ombclen;
          memset (m + 1, 0, ombclen - 1);
          m += ombclen;
          p += ombclen;
          outlen += ombclen;
          lengths_differ |= (mbclen != ombclen);
        }
    }

  *len_map_p = lengths_differ ? len_map : NULL;
  *n = p - out;
  *p = 0;
  return out;
}


bool
is_mb_middle (const char **good, const char *buf, const char *end,
              size_t match_len)
{
  const char *p = *good;
  const char *prev = p;
  mbstate_t cur_state;

  /* TODO: can be optimized for UTF-8.  */
  memset(&cur_state, 0, sizeof(mbstate_t));
  while (p < buf)
    {
      size_t mbclen = mbrlen(p, end - p, &cur_state);

      /* Store the beginning of the previous complete multibyte character.  */
      if (mbclen != (size_t) -2)
        prev = p;

      if (mbclen == (size_t) -1 || mbclen == (size_t) -2 || mbclen == 0)
        {
          /* An invalid sequence, or a truncated multibyte character.
             We treat it as a single byte character.  */
          mbclen = 1;
          memset(&cur_state, 0, sizeof cur_state);
        }
      p += mbclen;
    }

  *good = prev;

  if (p > buf)
    return true;

  /* P == BUF here.  */
  return 0 < match_len && match_len < mbrlen (p, end - p, &cur_state);
}
#endif /* MBS_SUPPORT */