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lookfor.c

/* This is the strcasestr inplementation of the GNU C Library.
   I includes it here in order to facility port raccess on some platforms
   that not includes this function. I have made some modifications in order
   to adecuate it to raccess. 
   
   Angel Ramos <seamus@salix.org>*/
   
/* Return the offset of one string within another.
   Copyright (C) 1994,1996,1997,1998,1999,2000 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C 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.

   The GNU C 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 the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

/*
 * My personal strstr() implementation that beats most other algorithms.
 * Until someone tells me otherwise, I assume that this is the
 * fastest implementation of strstr() in C.
 * I deliberately chose not to comment it.  You should have at least
 * as much fun trying to understand it, as I had to write it :-).
 *
 * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de   */

char *
lookfor (phaystack, pneedle)
     const char *phaystack;
     const char *pneedle;
{
  const unsigned char *haystack, *needle;
  char b, c;

  haystack = (const unsigned char *) phaystack;
  needle = (const unsigned char *) pneedle;

  b = tolower (*needle);
  if (b != '\0')
    {
      haystack--;                   /* possible ANSI violation */
      do
      {
        c = *++haystack;
        if (c == '\0')
          goto ret0;
      }
      while (tolower (c) != (int) b);

      c = tolower (*++needle);
      if (c == '\0')
      goto foundneedle;
      ++needle;
      goto jin;

      for (;;)
        {
          char a;
        const unsigned char *rhaystack, *rneedle;

        do
          {
            a = *++haystack;
            if (a == '\0')
            goto ret0;
            if (tolower (a) == (int) b)
            break;
            a = *++haystack;
            if (a == '\0')
            goto ret0;
shloop:
            ;
          }
          while (tolower (a) != (int) b);

jin:    a = *++haystack;
        if (a == '\0')
          goto ret0;

        if (tolower (a) != (int) c)
          goto shloop;

        rhaystack = haystack-- + 1;
        rneedle = needle;
        a = tolower (*rneedle);

        if (tolower (*rhaystack) == (int) a)
          do
            {
            if (a == '\0')
              goto foundneedle;
            ++rhaystack;
            a = tolower (*++needle);
            if (tolower (*rhaystack) != (int) a)
              break;
            if (a == '\0')
              goto foundneedle;
            ++rhaystack;
            a = tolower (*++needle);
            }
          while (tolower (*rhaystack) == (int) a);

        needle = rneedle;           /* took the register-poor approach */

        if (a == '\0')
          break;
        }
    }
foundneedle:
  return (char*) haystack;
ret0:
  return 0;
}

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