1 /* $OpenBSD: memmove.c,v 1.2 2015/08/31 02:53:57 guenther Exp $ */ 2 /*- 3 * Copyright (c) 1990 The Regents of the University of California. 4 * All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Chris Torek. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #include <string.h> 35 36 /* 37 * sizeof(word) MUST BE A POWER OF TWO 38 * SO THAT wmask BELOW IS ALL ONES 39 */ 40 typedef long word; /* "word" used for optimal copy speed */ 41 42 #define wsize sizeof(word) 43 #define wmask (wsize - 1) 44 45 /* 46 * Copy a block of memory, handling overlap. 47 */ 48 void * 49 memmove(void *dst0, const void *src0, size_t length) 50 { 51 char *dst = dst0; 52 const char *src = src0; 53 size_t t; 54 55 if (length == 0 || dst == src) /* nothing to do */ 56 goto done; 57 58 /* 59 * Macros: loop-t-times; and loop-t-times, t>0 60 */ 61 #define TLOOP(s) if (t) TLOOP1(s) 62 #define TLOOP1(s) do { s; } while (--t) 63 64 if ((unsigned long)dst < (unsigned long)src) { 65 /* 66 * Copy forward. 67 */ 68 t = (long)src; /* only need low bits */ 69 if ((t | (long)dst) & wmask) { 70 /* 71 * Try to align operands. This cannot be done 72 * unless the low bits match. 73 */ 74 if ((t ^ (long)dst) & wmask || length < wsize) 75 t = length; 76 else 77 t = wsize - (t & wmask); 78 length -= t; 79 TLOOP1(*dst++ = *src++); 80 } 81 /* 82 * Copy whole words, then mop up any trailing bytes. 83 */ 84 t = length / wsize; 85 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize); 86 t = length & wmask; 87 TLOOP(*dst++ = *src++); 88 } else { 89 /* 90 * Copy backwards. Otherwise essentially the same. 91 * Alignment works as before, except that it takes 92 * (t&wmask) bytes to align, not wsize-(t&wmask). 93 */ 94 src += length; 95 dst += length; 96 t = (long)src; 97 if ((t | (long)dst) & wmask) { 98 if ((t ^ (long)dst) & wmask || length <= wsize) 99 t = length; 100 else 101 t &= wmask; 102 length -= t; 103 TLOOP1(*--dst = *--src); 104 } 105 t = length / wsize; 106 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src); 107 t = length & wmask; 108 TLOOP(*--dst = *--src); 109 } 110 done: 111 return (dst0); 112 } 113 DEF_STRONG(memmove); 114
