/* Case-insensitive string comparison function.
   Copyright (C) 1998-1999, 2005-2010 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2007.

   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 of the License, 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, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include <string.h>

#include <ctype.h>

#include "mbuiter.h"

#define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))

/* Compare the initial segment of the character string STRING consisting of
   at most mbslen (PREFIX) characters with the character string PREFIX,
   ignoring case, returning less than, equal to or greater than zero if this
   initial segment is lexicographically less than, equal to or greater than
   PREFIX.
   Note: This function may, in multibyte locales, return 0 if STRING is of
   smaller length than PREFIX!  */
char *
mbspcasecmp (const char *string, const char *prefix)
{
  /* This is essentially the same as
       mbsncasecmp (string, prefix, mbslen (prefix))
     just with small optimizations.  */
  if (string == prefix)
    return (char *) (string + strlen (string));

  /* Be careful not to look at the entire extent of STRING or PREFIX until
     needed.  This is useful because when two strings differ, the difference is
     most often already in the very few first characters.  */
  if (MB_CUR_MAX > 1)
    {
      mbui_iterator_t iter1;
      mbui_iterator_t iter2;

      mbui_init (iter1, string);
      mbui_init (iter2, prefix);

      while (mbui_avail (iter1) && mbui_avail (iter2))
        {
          int cmp = mb_casecmp (mbui_cur (iter1), mbui_cur (iter2));

          if (cmp != 0)
            return NULL;

          mbui_advance (iter1);
          mbui_advance (iter2);
        }
      if (!mbui_avail (iter2))
        /* PREFIX equals STRING or is terminated before STRING.  */
        return (char *) mbui_cur_ptr (iter1);
      else
        /* STRING terminated before PREFIX.  */
        return NULL;
    }
  else
    {
      const unsigned char *p1 = (const unsigned char *) string;
      const unsigned char *p2 = (const unsigned char *) prefix;
      unsigned char c1, c2;

      for (; ; p1++, p2++)
        {
          c1 = TOLOWER (*p1);
          c2 = TOLOWER (*p2);

          if (c2 == '\0' || c1 != c2)
            break;
        }

      if (c2 == '\0')
        /* PREFIX equals STRING or is terminated before STRING.  */
        return (char *) p1;
      else
        /* STRING terminated before PREFIX.  */
        return NULL;
    }
}
