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/****************************************************************************
* lib/string/lib_memset.c
*
* Copyright (C) 2007, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdint.h>
#include <string.h>
#include <assert.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Can't support CONFIG_MEMSET_64BIT if the platform does not have 64-bit
* integer types.
*/
#ifndef CONFIG_HAVE_LONG_LONG
# undef CONFIG_MEMSET_64BIT
#endif
/****************************************************************************
* Global Functions
****************************************************************************/
#ifndef CONFIG_ARCH_MEMSET
void *memset(void *s, int c, size_t n)
{
#ifdef CONFIG_MEMSET_OPTSPEED
/* This version is optimized for speed (you could do better
* still by exploiting processor caching or memory burst
* knowledge.)
*/
uintptr_t addr = (uintptr_t)s;
uint16_t val16 = ((uint16_t)c << 8) | (uint16_t)c;
uint32_t val32 = ((uint32_t)val16 << 16) | (uint32_t)val16;
#ifdef CONFIG_MEMSET_64BIT
uint64_t val64 = ((uint64_t)val32 << 32) | (uint64_t)val32;
#endif
/* Make sure that there is something to be cleared */
if (n > 0)
{
/* Align to a 16-bit boundary */
if ((addr & 1) != 0)
{
*(uint8_t*)addr = (uint8_t)c;
addr += 1;
n -= 1;
}
/* Check if there are at least 16-bits left to be written */
if (n >= 2)
{
/* Align to a 32-bit boundary (we know that the destination
* address is already aligned to at least a 16-bit boundary).
*/
if ((addr & 3) != 0)
{
*(uint16_t*)addr = val16;
addr += 2;
n -= 2;
}
#ifndef CONFIG_MEMSET_64BIT
/* Loop while there are at least 32-bits left to be written */
while (n >= 4)
{
*(uint32_t*)addr = val32;
addr += 4;
n -= 4;
}
#else
/* Check if there are at least 32-bits left to be written */
if (n >= 4)
{
/* Align to a 64-bit boundary (we know that the destination
* address is already aligned to at least a 32-bit boundary).
*/
if ((addr & 7) != 0)
{
*(uint32_t*)addr = val32;
addr += 4;
n -= 4;
}
/* Loop while there are at least 64-bits left to be written */
while (n >= 8)
{
*(uint64_t*)addr = val64;
addr += 8;
n -= 8;
}
}
#endif
}
#ifdef CONFIG_MEMSET_64BIT
/* We may get here with n in the range 0..7. If n >= 4, then we should
* have 64-bit alignment.
*/
if (n >= 4)
{
*(uint32_t*)addr = val32;
addr += 4;
n -= 4;
}
#endif
/* We may get here under the following conditions:
*
* n = 0, addr may or may not be aligned
* n = 1, addr is aligned to at least a 16-bit boundary
* n = 2, addr is aligned to a 32-bit boundary
* n = 3, addr is aligned to a 32-bit boundary
*/
if (n >= 2)
{
*(uint16_t*)addr = val16;
addr += 2;
n -= 2;
}
if (n >= 1)
{
*(uint8_t*)addr = (uint8_t)c;
}
}
#else
/* This version is optimized for size */
unsigned char *p = (unsigned char*)s;
while (n-- > 0) *p++ = c;
#endif
return s;
}
#endif
|
