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/* Copyright (C) 2013-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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"
/* Find the length of S, but scan at most MAXLEN characters. If no
'\0' terminator is found in that many characters, return MAXLEN. */
size_t
__strnlen (const char *s, size_t maxlen)
{
/* When maxlen is 0, can't read any bytes or it might cause a page fault. */
if (maxlen == 0)
return 0;
/* Get an aligned pointer. */
const uintptr_t s_int = (uintptr_t) s;
const uint64_t *p = (const uint64_t *) (s_int & -8);
size_t bytes_read = sizeof (*p) - (s_int & (sizeof (*p) - 1));
/* Read and MASK the first word. */
uint64_t v = *p | MASK (s_int);
uint64_t bits;
while ((bits = __insn_v1cmpeqi (v, 0)) == 0)
{
if (bytes_read >= maxlen)
{
/* Read maxlen bytes and didn't find the terminator. */
return maxlen;
}
v = *++p;
bytes_read += sizeof (v);
}
/* Found '\0', check it is not larger than maxlen */
size_t len = ((const char *) p) + (CFZ (bits) >> 3) - s;
return (len < maxlen ? len : maxlen);
}
libc_hidden_def (__strnlen)
weak_alias (__strnlen, strnlen)
libc_hidden_def (strnlen)
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