mirror of
https://github.com/apache/nuttx.git
synced 2026-05-12 17:58:10 +08:00
anjiahao
7c96537a58
This allows the compiler to automatically identify which string functions can be compiled into libraries, and the compiler's internal implementation is faster than libc functions. Signed-off-by: anjiahao <anjiahao@xiaomi.com>
94 lines
2.7 KiB
C
94 lines
2.7 KiB
C
/****************************************************************************
|
|
* libs/libc/string/lib_bsdstrlen.c
|
|
*
|
|
* Copyright (c) 1994-2009 Red Hat, Inc. All rights reserved.
|
|
*
|
|
* This copyrighted material is made available to anyone wishing to use,
|
|
* modify, copy, or redistribute it subject to the terms and conditions
|
|
* of the BSD License. This program is distributed in the hope that
|
|
* it will be useful, but WITHOUT ANY WARRANTY expressed or implied,
|
|
* including the implied warranties of MERCHANTABILITY or FITNESS FOR
|
|
* A PARTICULAR PURPOSE. A copy of this license is available at
|
|
* http://www.opensource.org/licenses. Any Red Hat trademarks that are
|
|
* incorporated in the source code or documentation are not subject to
|
|
* the BSD License and may only be used or replicated with the express
|
|
* permission of Red Hat, Inc.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <nuttx/config.h>
|
|
#include <sys/types.h>
|
|
#include <string.h>
|
|
|
|
#include "libc.h"
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
#define LBLOCKSIZE (sizeof(long))
|
|
#define UNALIGNED(x) ((long)(uintptr_t)(x) & (LBLOCKSIZE - 1))
|
|
|
|
/* Macros for detecting endchar */
|
|
|
|
#if LONG_MAX == 2147483647
|
|
# define DETECTNULL(x) (((x) - 0x01010101) & ~(x) & 0x80808080)
|
|
#elif LONG_MAX == 9223372036854775807
|
|
/* Nonzero if x (a long int) contains a NULL byte. */
|
|
|
|
# define DETECTNULL(x) (((x) - 0x0101010101010101) & ~(x) & 0x8080808080808080)
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
#if !defined(CONFIG_LIBC_ARCH_STRLEN) && defined(LIBC_BUILD_STRLEN)
|
|
#undef strlen
|
|
no_builtin("strlen")
|
|
nosanitize_address
|
|
size_t strlen(FAR const char *s)
|
|
{
|
|
FAR const char *start = s;
|
|
FAR unsigned long *aligned_addr;
|
|
|
|
/* Align the pointer, so we can search a word at a time. */
|
|
|
|
while (UNALIGNED(s))
|
|
{
|
|
if (!*s)
|
|
{
|
|
return s - start;
|
|
}
|
|
|
|
s++;
|
|
}
|
|
|
|
/* If the string is word-aligned, we can check for the presence of
|
|
* a null in each word-sized block.
|
|
*/
|
|
|
|
aligned_addr = (FAR unsigned long *)s;
|
|
while (!DETECTNULL(*aligned_addr))
|
|
{
|
|
aligned_addr++;
|
|
}
|
|
|
|
/* Once a null is detected, we check each byte in that block for a
|
|
* precise position of the null.
|
|
*/
|
|
|
|
s = (FAR char *)aligned_addr;
|
|
while (*s)
|
|
{
|
|
s++;
|
|
}
|
|
|
|
return s - start;
|
|
}
|
|
#endif
|