| /* Copyright (C) 2011-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011. |
| |
| 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/>. */ |
| |
| #include <string.h> |
| #include <stdint.h> |
| #include "string-endian.h" |
| |
| void * |
| __memchr (const void *s, int c, size_t n) |
| { |
| const uint64_t *last_word_ptr; |
| const uint64_t *p; |
| const char *last_byte_ptr; |
| uintptr_t s_int; |
| uint64_t goal, before_mask, v, bits; |
| char *ret; |
| |
| if (__builtin_expect (n == 0, 0)) |
| { |
| /* Don't dereference any memory if the array is empty. */ |
| return NULL; |
| } |
| |
| /* Get an aligned pointer. */ |
| s_int = (uintptr_t) s; |
| p = (const uint64_t *) (s_int & -8); |
| |
| /* Create eight copies of the byte for which we are looking. */ |
| goal = copy_byte(c); |
| |
| /* Read the first word, but munge it so that bytes before the array |
| will not match goal. */ |
| before_mask = MASK (s_int); |
| v = (*p | before_mask) ^ (goal & before_mask); |
| |
| /* Compute the address of the last byte. */ |
| last_byte_ptr = (const char *) s + n - 1; |
| |
| /* Handle possible addition overflow. */ |
| if (__glibc_unlikely ((uintptr_t) last_byte_ptr < (uintptr_t) s)) |
| last_byte_ptr = (const char *) UINTPTR_MAX; |
| |
| /* Compute the address of the word containing the last byte. */ |
| last_word_ptr = (const uint64_t *) ((uintptr_t) last_byte_ptr & -8); |
| |
| while ((bits = v1cmpeq (v, goal)) == 0) |
| { |
| if (__builtin_expect (p == last_word_ptr, 0)) |
| { |
| /* We already read the last word in the array, so give up. */ |
| return NULL; |
| } |
| v = *++p; |
| } |
| |
| /* We found a match, but it might be in a byte past the end |
| of the array. */ |
| ret = ((char *) p) + (CFZ (bits) >> 3); |
| return (ret <= last_byte_ptr) ? ret : NULL; |
| } |
| weak_alias (__memchr, memchr) |
| libc_hidden_builtin_def (memchr) |