/* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2018 Free Software

   Foundation, Inc.

   This file is part of the GNU C Library.

   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, see <https://www.gnu.org/licenses/>.  */

/* This particular implementation was written by Eric Blake, 2008.  */

#ifndef _LIBC

# include <config.h>

#endif

/* Specification of strstr.  */

#include <string.h>

#include <stdbool.h>

#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)))

#include "str-two-way.h"

/* Return the first occurrence of NEEDLE in HAYSTACK.  Return HAYSTACK

   if NEEDLE is empty, otherwise NULL if NEEDLE is not found in

   HAYSTACK.  */

char *

strstr (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 &= *haystack++ == *needle++;

  if (*needle)

    return NULL;

  if (ok)

    return (char *) haystack_start;

  /* Reduce the size of haystack using strchr, since it has a smaller

     linear coefficient than the Two-Way algorithm.  */

  needle_len = needle - needle_start;

  haystack = strchr (haystack_start + 1, *needle_start);

  if (!haystack || __builtin_expect (needle_len == 1, 0))

    return (char *) haystack;

  needle -= needle_len;

  haystack_len = (haystack > haystack_start + needle_len ? 1

                  : needle_len + haystack_start - haystack);

  /* 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, needle_len);

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

                              (const unsigned char *) needle, needle_len);

}

#undef LONG_NEEDLE_THRESHOLD