nuttx/libs/libc/string/lib_bsdstrcmp.c
Xiang Xiao d1dc791d11 libs/libc/string: Add 4-byte alignment middle path for BSD functions.
libc_data_t is 8 bytes wide, so a buffer which is 4-byte but not
8-byte aligned falls back to the byte at a time loop.  Add a 32-bit
middle path so such buffers still handle four bytes per iteration.

* Add DETECTNULL32/DETECTCHAR32, UNALIGNED4/UNALIGNED4_X,
  LITTLEBLOCKSIZE4/BIGBLOCKSIZE4 and TOO_SMALL4 to libs/libc/libc.h.
* Take the new path in memccpy, memcmp, memcpy, memset, stpcpy,
  stpncpy, strcmp, strcpy, strncmp and strncpy when both pointers are
  4-byte aligned but the 8-byte path can't be used.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
2026-08-17 10:47:33 +02:00

95 lines
2.7 KiB
C

/****************************************************************************
* libs/libc/string/lib_bsdstrcmp.c
*
* SPDX-License-Identifier: BSD
* SPDX-FileCopyrightText: 1994-2009 Red Hat, Inc. All rights reserved
*
* 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 <string.h>
#include "libc.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
#if !defined(CONFIG_LIBC_ARCH_STRCMP) && defined(LIBC_BUILD_STRCMP)
#undef strcmp
no_builtin("strcmp")
nosanitize_address
int strcmp(FAR const char *cs, FAR const char *ct)
{
/* If cs or ct are unaligned, then compare bytes. */
if (!UNALIGNED(cs, ct))
{
FAR libc_data_t *a1 = (FAR libc_data_t *)cs;
FAR libc_data_t *a2 = (FAR libc_data_t *)ct;
while (*a1 == *a2)
{
if (DETECTNULL(*a1))
{
return 0;
}
a1++;
a2++;
}
cs = (FAR char *)a1;
ct = (FAR char *)a2;
}
else if (!UNALIGNED4(cs, ct))
{
FAR uint32_t *a1 = (FAR uint32_t *)cs;
FAR uint32_t *a2 = (FAR uint32_t *)ct;
while (*a1 == *a2)
{
if (DETECTNULL32(*a1))
{
return 0;
}
a1++;
a2++;
}
cs = (FAR char *)a1;
ct = (FAR char *)a2;
}
while (*cs != '\0' && *cs == *ct)
{
cs++;
ct++;
}
return (*(FAR unsigned char *)cs) - (*(FAR unsigned char *)ct);
}
#endif