86 lines
1.7 KiB
C
86 lines
1.7 KiB
C
/*
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* Copyright (c) 2010, ETH Zurich.
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* All rights reserved.
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*
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* This file is distributed under the terms in the attached LICENSE file.
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* If you do not find this file, copies can be found by writing to:
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* ETH Zurich D-INFK, Universitaetstrasse 6, CH-8092 Zurich. Attn: Systems Group.
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*/
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#include <string.h>
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#include <stdint.h>
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#define LOWBITS (sizeof(uintptr_t)-1)
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void *memmove(void *s1, const void *s2, size_t n)
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{
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uintptr_t from = (uintptr_t)s2;
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uintptr_t to = (uintptr_t)s1;
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if (to <= from) {
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// Work forwards
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if (((from ^ to) & LOWBITS) == 0) {
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// They have the same alignment
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// Copy bytes until aligned to a word boundary
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while (n != 0 && ((from & LOWBITS) != 0)) {
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*(char *)to = *(const char *)from;
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from++;
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to++;
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n--;
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}
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// Copy words
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while(n >= sizeof(uintptr_t)) {
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*(uintptr_t *)to = *(const uintptr_t *)from;
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from += sizeof(uintptr_t);
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to += sizeof(uintptr_t);
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n -= sizeof(uintptr_t);
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}
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}
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// Copy (remaining) bytes
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while (n != 0) {
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*(char *)to = *(const char *)from;
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from++;
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to++;
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n--;
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}
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}
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else {
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// Work backwards
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from += n;
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to += n;
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if (((from ^ to) & LOWBITS) == 0) {
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// They have the same alignment
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// Copy bytes until aligned to a word boundary
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while (n != 0 && ((from & LOWBITS) != 0)) {
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from--;
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to--;
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*(char *)to = *(const char *)from;
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n--;
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}
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// Copy words
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while(n >= sizeof(uintptr_t)) {
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from -= sizeof(uintptr_t);
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to -= sizeof(uintptr_t);
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*(uintptr_t *)to = *(const uintptr_t *)from;
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n -= sizeof(uintptr_t);
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}
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}
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// Copy (remaining) bytes
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while (n != 0) {
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from--;
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to--;
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*(char *)to = *(const char *)from;
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n--;
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}
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}
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return s1;
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}
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