93 lines
2.7 KiB
C
93 lines
2.7 KiB
C
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/****************************************************************************
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* libs/libc/string/lib_bsdstrlen.c
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*
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* Copyright (c) 1994-2009 Red Hat, Inc. All rights reserved.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the BSD License. This program is distributed in the hope that
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* it will be useful, but WITHOUT ANY WARRANTY expressed or implied,
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* including the implied warranties of MERCHANTABILITY or FITNESS FOR
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* A PARTICULAR PURPOSE. A copy of this license is available at
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* http://www.opensource.org/licenses. Any Red Hat trademarks that are
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* incorporated in the source code or documentation are not subject to
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* the BSD License and may only be used or replicated with the express
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* permission of Red Hat, Inc.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <string.h>
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#include "libc.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define LBLOCKSIZE (sizeof(long))
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#define UNALIGNED(x) ((long)(uintptr_t)(x) & (LBLOCKSIZE - 1))
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/* Macros for detecting endchar */
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#if LONG_MAX == 2147483647
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# define DETECTNULL(x) (((x) - 0x01010101) & ~(x) & 0x80808080)
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#elif LONG_MAX == 9223372036854775807
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/* Nonzero if x (a long int) contains a NULL byte. */
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# define DETECTNULL(x) (((x) - 0x0101010101010101) & ~(x) & 0x8080808080808080)
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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#if !defined(CONFIG_LIBC_ARCH_STRLEN) && defined(LIBC_BUILD_STRLEN)
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#undef strlen /* See mm/README.txt */
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nosanitize_address
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size_t strlen(FAR const char *s)
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{
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FAR const char *start = s;
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FAR unsigned long *aligned_addr;
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/* Align the pointer, so we can search a word at a time. */
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while (UNALIGNED(s))
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{
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if (!*s)
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{
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return s - start;
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}
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s++;
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}
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/* If the string is word-aligned, we can check for the presence of
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* a null in each word-sized block.
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*/
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aligned_addr = (FAR unsigned long *)s;
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while (!DETECTNULL(*aligned_addr))
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{
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aligned_addr++;
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}
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/* Once a null is detected, we check each byte in that block for a
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* precise position of the null.
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*/
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s = (FAR char *)aligned_addr;
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while (*s)
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{
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s++;
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}
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return s - start;
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}
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#endif
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