073a96bb2c
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5242 42af7a65-404d-4744-a932-0658087f49c3
144 lines
4.3 KiB
C
144 lines
4.3 KiB
C
/************************************************************
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* lib/string/lib_memset.c
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*
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* Copyright (C) 2007, 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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************************************************************/
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/************************************************************
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* Compilation Switches
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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 <stdint.h>
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#include <string.h>
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#include <assert.h>
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/************************************************************
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* Global Functions
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************************************************************/
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#ifndef CONFIG_ARCH_MEMSET
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void *memset(void *s, int c, size_t n)
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{
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#ifdef CONFIG_MEMSET_OPTSPEED
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/* This version is optimized for speed (you could do better
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* still by exploiting processor caching or memory burst
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* knowledge. 64-bit support might improve performance as
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* well.
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*/
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uintptr_t addr = (uintptr_t)s;
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uint16_t val16 = ((uint16_t)c << 8) | (uint16_t)c;
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uint32_t val32 = ((uint32_t)val16 << 16) | (uint32_t)val16;
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/* Make sure that there is something to be cleared */
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if (n > 0)
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{
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/* Align to a 16-bit boundary */
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if ((addr & 1) != 0)
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{
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*(uint8_t*)addr = (uint8_t)c;
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addr += 1;
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n -= 1;
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}
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/* Check if there are at least 16-bits left to be zeroed */
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if (n >= 2)
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{
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/* Align to a 32-bit boundary (we know that the destination
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* address is already aligned to at least a 16-bit boundary).
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*/
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if ((addr & 3) != 0)
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{
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*(uint16_t*)addr = val16;
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addr += 2;
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n -= 2;
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}
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/* Loop while there are at least 32-bits left to be zeroed */
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while (n >= 4)
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{
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*(uint32_t*)addr = val32;
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addr += 4;
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n -= 4;
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}
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}
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/* We may get here under the following conditions:
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*
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* n = 0, addr may or may not be aligned
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* n = 1, addr may or may not be aligned
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* n = 2, addr is aligned to a 32-bit boundary
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* n = 3, addr is aligned to a 32-bit boundary
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*/
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switch (n)
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{
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default:
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case 0:
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DEBUGASSERT(n == 0);
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break;
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case 2:
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*(uint16_t*)addr = val16;
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break;
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case 3:
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*(uint16_t*)addr = val16;
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addr += 2;
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case 1:
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*(uint8_t*)addr = (uint8_t)c;
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break;
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}
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}
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#else
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/* This version is optimized for size */
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unsigned char *p = (unsigned char*)s;
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while (n-- > 0) *p++ = c;
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#endif
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return s;
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}
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#endif
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