1 /* $OpenBSD: bcopy.c,v 1.2 2017/01/24 08:09:05 kettenis Exp $ */ 2 3 /*- 4 * Copyright (c) 1990 The Regents of the University of California. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/types.h> 36 #include <sys/systm.h> 37 38 #undef bcopy 39 40 /* 41 * sizeof(word) MUST BE A POWER OF TWO 42 * SO THAT wmask BELOW IS ALL ONES 43 */ 44 typedef long word; /* "word" used for optimal copy speed */ 45 46 #define wsize sizeof(word) 47 #define wmask (wsize - 1) 48 49 /* 50 * Copy a block of memory, handling overlap. 51 * This is the routine that actually implements 52 * (the portable versions of) bcopy, memcpy, and memmove. 53 */ 54 void 55 bcopy(const void *src0, void *dst0, size_t length) 56 { 57 char *dst = dst0; 58 const char *src = src0; 59 size_t t; 60 61 if (length == 0 || dst == src) /* nothing to do */ 62 goto done; 63 64 /* 65 * Macros: loop-t-times; and loop-t-times, t>0 66 */ 67 #define TLOOP(s) if (t) TLOOP1(s) 68 #define TLOOP1(s) do { s; } while (--t) 69 70 if ((unsigned long)dst < (unsigned long)src) { 71 /* 72 * Copy forward. 73 */ 74 t = (long)src; /* only need low bits */ 75 if ((t | (long)dst) & wmask) { 76 /* 77 * Try to align operands. This cannot be done 78 * unless the low bits match. 79 */ 80 if ((t ^ (long)dst) & wmask || length < wsize) 81 t = length; 82 else 83 t = wsize - (t & wmask); 84 length -= t; 85 TLOOP1(*dst++ = *src++); 86 } 87 /* 88 * Copy whole words, then mop up any trailing bytes. 89 */ 90 t = length / wsize; 91 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize); 92 t = length & wmask; 93 TLOOP(*dst++ = *src++); 94 } else { 95 /* 96 * Copy backwards. Otherwise essentially the same. 97 * Alignment works as before, except that it takes 98 * (t&wmask) bytes to align, not wsize-(t&wmask). 99 */ 100 src += length; 101 dst += length; 102 t = (long)src; 103 if ((t | (long)dst) & wmask) { 104 if ((t ^ (long)dst) & wmask || length <= wsize) 105 t = length; 106 else 107 t &= wmask; 108 length -= t; 109 TLOOP1(*--dst = *--src); 110 } 111 t = length / wsize; 112 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src); 113 t = length & wmask; 114 TLOOP(*--dst = *--src); 115 } 116 done: 117 return; 118 } 119