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75 lines
2.4 KiB
C
75 lines
2.4 KiB
C
/* Copyright (C) 2011 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <string.h>
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#include <stdint.h>
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#include "string-endian.h"
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void *
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__memchr (const void *s, int c, size_t n)
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{
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const uint64_t *last_word_ptr;
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const uint64_t *p;
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const char *last_byte_ptr;
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uintptr_t s_int;
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uint64_t goal, before_mask, v, bits;
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char *ret;
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if (__builtin_expect (n == 0, 0))
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{
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/* Don't dereference any memory if the array is empty. */
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return NULL;
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}
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/* Get an aligned pointer. */
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s_int = (uintptr_t) s;
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p = (const uint64_t *) (s_int & -8);
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/* Create eight copies of the byte for which we are looking. */
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goal = 0x0101010101010101ULL * (uint8_t) c;
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/* Read the first word, but munge it so that bytes before the array
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will not match goal. */
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before_mask = MASK (s_int);
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v = (*p | before_mask) ^ (goal & before_mask);
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/* Compute the address of the last byte. */
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last_byte_ptr = (const char *) s + n - 1;
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/* Compute the address of the word containing the last byte. */
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last_word_ptr = (const uint64_t *) ((uintptr_t) last_byte_ptr & -8);
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while ((bits = __insn_v1cmpeq (v, goal)) == 0)
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{
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if (__builtin_expect (p == last_word_ptr, 0))
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{
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/* We already read the last word in the array, so give up. */
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return NULL;
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}
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v = *++p;
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}
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/* We found a match, but it might be in a byte past the end
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of the array. */
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ret = ((char *) p) + (CFZ (bits) >> 3);
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return (ret <= last_byte_ptr) ? ret : NULL;
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}
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weak_alias (__memchr, memchr)
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libc_hidden_builtin_def (memchr)
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