mirror of https://gitee.com/openkylin/linux.git
48 lines
1.4 KiB
C
48 lines
1.4 KiB
C
/*
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* Copyright 2013 Tilera Corporation. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation, version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for
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* more details.
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*/
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#include <linux/types.h>
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#include <linux/string.h>
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#include <linux/module.h>
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size_t strnlen(const char *s, size_t count)
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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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size_t bytes_read = sizeof(*p) - (s_int & (sizeof(*p) - 1));
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size_t len;
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uint32_t v, bits;
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/* Avoid page fault risk by not reading any bytes when count is 0. */
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if (count == 0)
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return 0;
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/* Read first word, but force bytes before the string to be nonzero. */
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v = *p | ((1 << ((s_int << 3) & 31)) - 1);
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while ((bits = __insn_seqb(v, 0)) == 0) {
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if (bytes_read >= count) {
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/* Read COUNT bytes and didn't find the terminator. */
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return count;
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}
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v = *++p;
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bytes_read += sizeof(v);
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}
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len = ((const char *) p) + (__insn_ctz(bits) >> 3) - s;
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return (len < count ? len : count);
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}
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EXPORT_SYMBOL(strnlen);
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