mirror of
https://github.com/apache/nuttx.git
synced 2026-05-16 13:56:00 +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>
119 lines
3.3 KiB
C
119 lines
3.3 KiB
C
/****************************************************************************
|
|
* libs/libc/string/lib_bsdstrncmp.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))
|
|
|
|
/* Nonzero if either x or y is not aligned on a "long" boundary. */
|
|
|
|
#define UNALIGNED(x, y) \
|
|
(((long)(uintptr_t)(x) & (sizeof(long) - 1)) | ((long)(uintptr_t)(y) & (sizeof(long) - 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_STRNCMP) && defined(LIBC_BUILD_STRNCMP)
|
|
#undef strncmp
|
|
no_builtin("strncmp")
|
|
nosanitize_address
|
|
int strncmp(FAR const char *cs, FAR const char *ct, size_t nb)
|
|
{
|
|
FAR unsigned long *a1;
|
|
FAR unsigned long *a2;
|
|
|
|
if (nb == 0)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
/* If cs or ct are unaligned, then compare bytes. */
|
|
|
|
if (!UNALIGNED(cs, ct))
|
|
{
|
|
/* If cs and ct are word-aligned, compare them a word at a time. */
|
|
|
|
a1 = (FAR unsigned long *)cs;
|
|
a2 = (FAR unsigned long *)ct;
|
|
while (nb >= LBLOCKSIZE && *a1 == *a2)
|
|
{
|
|
nb -= LBLOCKSIZE;
|
|
|
|
/* If we've run out of bytes or hit a null, return zero
|
|
* since we already know *a1 == *a2.
|
|
*/
|
|
|
|
if (nb == 0 || DETECTNULL(*a1))
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
a1++;
|
|
a2++;
|
|
}
|
|
|
|
/* A difference was detected in last few bytes of cs, so search
|
|
* bytewise.
|
|
*/
|
|
|
|
cs = (FAR char *)a1;
|
|
ct = (FAR char *)a2;
|
|
}
|
|
|
|
while (nb-- > 0 && *cs == *ct)
|
|
{
|
|
/* If we've run out of bytes or hit a null, return zero
|
|
* since we already know *cs == *ct.
|
|
*/
|
|
|
|
if (nb == 0 || *cs == '\0')
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
cs++;
|
|
ct++;
|
|
}
|
|
|
|
return *cs - *ct;
|
|
}
|
|
#endif
|