/* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2024 Free Software Foundation, Inc. This file is part of the GNU C Library. 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 . */ /* This particular implementation was written by Eric Blake, 2008. */ #ifndef _LIBC # include #endif /* Specification of memmem. */ #include #define RETURN_TYPE void * #define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l)) #include "str-two-way.h" /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in HAYSTACK. */ void * memmem (const void *haystack_start, size_t haystack_len, const void *needle_start, size_t needle_len) { /* 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. */ const unsigned char *haystack = (const unsigned char *) haystack_start; const unsigned char *needle = (const unsigned char *) needle_start; if (needle_len == 0) /* The first occurrence of the empty string is deemed to occur at the beginning of the string. */ return (void *) haystack; /* Sanity check, otherwise the loop might search through the whole memory. */ if (__builtin_expect (haystack_len < needle_len, 0)) return NULL; /* Use optimizations in memchr when possible, to reduce the search size of haystack using a linear algorithm with a smaller coefficient. However, avoid memchr for long needles, since we can often achieve sublinear performance. */ if (needle_len < LONG_NEEDLE_THRESHOLD) { haystack = memchr (haystack, *needle, haystack_len); if (!haystack || __builtin_expect (needle_len == 1, 0)) return (void *) haystack; haystack_len -= haystack - (const unsigned char *) haystack_start; if (haystack_len < needle_len) return NULL; return two_way_short_needle (haystack, haystack_len, needle, needle_len); } else return two_way_long_needle (haystack, haystack_len, needle, needle_len); } #undef LONG_NEEDLE_THRESHOLD