/* c-strcasestr.c -- case insensitive substring search in C locale

   Copyright (C) 2005-2023 Free Software Foundation, Inc.

   Written by Bruno Haible <bruno@clisp.org>, 2005.

   This file 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 file 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 program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include "c-strcasestr.h"

#include <string.h>

#include "c-ctype.h"

#include "c-strcase.h"

/* Two-Way algorithm.  */

#define RETURN_TYPE char *

#define AVAILABLE(h, h_l, j, n_l)                       \

  (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l))     \

   && ((h_l) = (j) + (n_l)))

#define CANON_ELEMENT c_tolower

#define CMP_FUNC(p1, p2, l)                             \

  c_strncasecmp ((const char *) (p1), (const char *) (p2), l)

#include "str-two-way.h"

/* Find the first occurrence of NEEDLE in HAYSTACK, using case-insensitive

   comparison from the C locale, regardless of the current locale.  */

char *

c_strcasestr (const char *haystack_start, const char *needle_start)

{

  const char *haystack = haystack_start;

  const char *needle = needle_start;

  size_t needle_len; /* Length of NEEDLE.  */

  size_t haystack_len; /* Known minimum length of HAYSTACK.  */

  bool ok = true; /* True if NEEDLE is prefix of HAYSTACK.  */

  /* Determine length of NEEDLE, and in the process, make sure

     HAYSTACK is at least as long (no point processing all of a long

     NEEDLE if HAYSTACK is too short).  */

  while (*haystack && *needle)

    ok &= (c_tolower ((unsigned char) *haystack++)

           == c_tolower ((unsigned char) *needle++));

  if (*needle)

    return NULL;

  if (ok)

    return (char *) haystack_start;

  needle_len = needle - needle_start;

  haystack = haystack_start + 1;

  haystack_len = needle_len - 1;

  /* Perform the search.  Abstract memory is considered to be an array

     of 'unsigned char' values, not an array of 'char' values.  See

     ISO C 99 section 6.2.6.1.  */

  if (needle_len < LONG_NEEDLE_THRESHOLD)

    return two_way_short_needle ((const unsigned char *) haystack,

                                 haystack_len,

                                 (const unsigned char *) needle_start,

                                 needle_len);

  return two_way_long_needle ((const unsigned char *) haystack, haystack_len,

                              (const unsigned char *) needle_start,

                              needle_len);

}

#undef LONG_NEEDLE_THRESHOLD