118 lines
3.5 KiB
C
118 lines
3.5 KiB
C
/*
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* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
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* The President and Fellows of Harvard College.
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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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* 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 the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be 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 UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* This file is shared between libc and the kernel, so don't put anything
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* in here that won't work in both contexts.
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*/
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#ifdef _KERNEL
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#include <types.h>
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#include <lib.h>
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#else
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#include <stdint.h>
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#include <string.h>
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#endif
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/*
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* C standard function - copy a block of memory, handling overlapping
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* regions correctly.
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*/
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void *
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memmove(void *dst, const void *src, size_t len)
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{
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size_t i;
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/*
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* If the buffers don't overlap, it doesn't matter what direction
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* we copy in. If they do, it does, so just assume they always do.
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* We don't concern ourselves with the possibility that the region
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* to copy might roll over across the top of memory, because it's
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* not going to happen.
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*
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* If the destination is above the source, we have to copy
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* back to front to avoid overwriting the data we want to
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* copy.
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*
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* dest: dddddddd
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* src: ssssssss ^
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* | ^ |___|
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* |___|
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*
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* If the destination is below the source, we have to copy
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* front to back.
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*
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* dest: dddddddd
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* src: ^ ssssssss
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* |___| ^ |
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* |___|
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*/
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if ((uintptr_t)dst < (uintptr_t)src) {
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/*
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* As author/maintainer of libc, take advantage of the
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* fact that we know memcpy copies forwards.
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*/
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return memcpy(dst, src, len);
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}
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/*
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* Copy by words in the common case. Look in memcpy.c for more
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* information.
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*/
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if ((uintptr_t)dst % sizeof(long) == 0 &&
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(uintptr_t)src % sizeof(long) == 0 &&
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len % sizeof(long) == 0) {
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long *d = dst;
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const long *s = src;
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/*
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* The reason we copy index i-1 and test i>0 is that
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* i is unsigned -- so testing i>=0 doesn't work.
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*/
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for (i=len/sizeof(long); i>0; i--) {
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d[i-1] = s[i-1];
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}
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}
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else {
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char *d = dst;
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const char *s = src;
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for (i=len; i>0; i--) {
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d[i-1] = s[i-1];
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}
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}
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return dst;
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}
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