diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-06 01:16:24 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-06 01:16:24 +0000 |
commit | 9221dca64f0c8b5de72727491e41cf63e902eaab (patch) | |
tree | d8cbbf520eb4b5c656a54b2e36947008dcb751ad /gl/lib/memmem.c | |
parent | Initial commit. (diff) | |
download | man-db-upstream.tar.xz man-db-upstream.zip |
Adding upstream version 2.8.5.upstream/2.8.5upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'gl/lib/memmem.c')
-rw-r--r-- | gl/lib/memmem.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/gl/lib/memmem.c b/gl/lib/memmem.c new file mode 100644 index 0000000..12ae24f --- /dev/null +++ b/gl/lib/memmem.c @@ -0,0 +1,71 @@ +/* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2019 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 memmem. */ +#include <string.h> + +#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 |