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40 lines
1.4 KiB
C
40 lines
1.4 KiB
C
/* Copyright (C) 2011-2017 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, see
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<http://www.gnu.org/licenses/>. */
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#include <string.h>
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#include <stdint.h>
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size_t
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strlen (const char *s)
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{
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/* Get an aligned pointer. */
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const uintptr_t s_int = (uintptr_t) s;
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const uint32_t *p = (const uint32_t *) (s_int & -4);
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/* Read the first word, but force bytes before the string to be nonzero.
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This expression works because we know shift counts are taken mod 32. */
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uint32_t v = *p | ((1 << (s_int << 3)) - 1);
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uint32_t bits;
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while ((bits = __insn_seqb (v, 0)) == 0)
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v = *++p;
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return ((const char *) p) + (__insn_ctz (bits) >> 3) - s;
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}
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libc_hidden_builtin_def (strlen)
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