new module 'c-strcasestr'

[Bruno Haible]

Likewise, here is a module for case-insensitive string search. Also needed
by GNU gettext.

Objections? Comments?


============================= modules/c-strcasestr =============================
Description:
Case-insensitive searching in a string in C locale.

Files:
lib/c-strcasestr.h
lib/c-strcasestr.c

Depends-on:
c-ctype

configure.ac:

Makefile.am:
lib_SOURCES += c-strcasestr.h c-strcasestr.c

Include:
"c-strcasestr.h"

License:
LGPL

Maintainer:
Bruno Haible

============================= lib/c-strcasestr.h =============================
/* Case-insensitive searching in a string in C locale.
   Copyright (C) 2005 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 2, 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.  */

#ifndef C_STRCASESTR_H
#define C_STRCASESTR_H


#ifdef __cplusplus
extern "C" {
#endif


/* Find the first occurrence of NEEDLE in HAYSTACK, using case-insensitive
   comparison.  */
extern char *c_strcasestr (const char *haystack, const char *needle);


#ifdef __cplusplus
}
#endif


#endif /* C_STRCASESTR_H */
============================= lib/c-strcasestr.c =============================
/* c-strcasestr.c -- case insensitive substring search in C locale
   Copyright (C) 2005 Free Software Foundation, Inc.
   Written by Bruno Haible <address@hidden>, 2005.

   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 2, 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.  */

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

/* Specification.  */
#include "c-strcasestr.h"

#include <stddef.h>

#include "c-ctype.h"

/* Find the first occurrence of NEEDLE in HAYSTACK, using case-insensitive
   comparison.
   Note: This function may, in multibyte locales, return success even if
   strlen (haystack) < strlen (needle) !  */
char *
c_strcasestr (const char *haystack, const char *needle)
{
  /* Be careful not to look at the entire extent of haystack or needle
     until needed.  This is useful because of these two cases:
       - haystack may be very long, and a match of needle found early,
       - needle may be very long, and not even a short initial segment of
         needle may be found in haystack.  */
  if (*needle != '\0')
    {
      /* Speed up the following searches of needle by caching its first
         character.  */
      unsigned char b = c_tolower ((unsigned char) *needle);

      needle++;
      for (;; haystack++)
        {
          if (*haystack == '\0')
            /* No match.  */
            return NULL;
          if (c_tolower ((unsigned char) *haystack) == b)
            /* The first character matches.  */
            {
              const char *rhaystack = haystack + 1;
              const char *rneedle = needle;

              for (;; rhaystack++, rneedle++)
                {
                  if (*rneedle == '\0')
                    /* Found a match.  */
                    return (char *) haystack;
                  if (*rhaystack == '\0')
                    /* No match.  */
                    return NULL;
                  if (c_tolower ((unsigned char) *rhaystack)
                      != c_tolower ((unsigned char) *rneedle))
                    /* Nothing in this round.  */
                    break;
                }
            }
        }
    }
  else
    return (char *) haystack;
}
===============================================================================