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glibc/string/strstr.c
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/* Return the offset of one string within another. | |
Copyright (C) 1994-2012 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, see | |
<http://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> | |
#ifndef _LIBC | |
# define __builtin_expect(expr, val) (expr) | |
#endif | |
#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 AVAILABLE1(h, h_l, j, n_l) (true) | |
#define AVAILABLE2(h, h_l, j, n_l) AVAILABLE (h, h_l, j, n_l) | |
#define RET0_IF_0(a) if (!a) goto ret0 | |
#define AVAILABLE1_USES_J (0) | |
#include "str-two-way.h" | |
#undef strstr | |
#ifndef STRSTR | |
#define STRSTR strstr | |
#endif | |
/* 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); | |
} | |
libc_hidden_builtin_def (strstr) | |
#undef LONG_NEEDLE_THRESHOLD |