1 /* $OpenBSD: bcopy.c,v 1.1 2013/06/13 04:33:26 deraadt 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 /* 39 * sizeof(word) MUST BE A POWER OF TWO 40 * SO THAT wmask BELOW IS ALL ONES 41 */ 42 typedef long word; /* "word" used for optimal copy speed */ 43 44 #define wsize sizeof(word) 45 #define wmask (wsize - 1) 46 47 /* 48 * Copy a block of memory, handling overlap. 49 * This is the routine that actually implements 50 * (the portable versions of) bcopy, memcpy, and memmove. 51 */ 52 void 53 bcopy(const void *src0, void *dst0, size_t length) 54 { 55 char *dst = dst0; 56 const char *src = src0; 57 size_t t; 58 59 if (length == 0 || dst == src) /* nothing to do */ 60 goto done; 61 62 /* 63 * Macros: loop-t-times; and loop-t-times, t>0 64 */ 65 #define TLOOP(s) if (t) TLOOP1(s) 66 #define TLOOP1(s) do { s; } while (--t) 67 68 if ((unsigned long)dst < (unsigned long)src) { 69 /* 70 * Copy forward. 71 */ 72 t = (long)src; /* only need low bits */ 73 if ((t | (long)dst) & wmask) { 74 /* 75 * Try to align operands. This cannot be done 76 * unless the low bits match. 77 */ 78 if ((t ^ (long)dst) & wmask || length < wsize) 79 t = length; 80 else 81 t = wsize - (t & wmask); 82 length -= t; 83 TLOOP1(*dst++ = *src++); 84 } 85 /* 86 * Copy whole words, then mop up any trailing bytes. 87 */ 88 t = length / wsize; 89 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize); 90 t = length & wmask; 91 TLOOP(*dst++ = *src++); 92 } else { 93 /* 94 * Copy backwards. Otherwise essentially the same. 95 * Alignment works as before, except that it takes 96 * (t&wmask) bytes to align, not wsize-(t&wmask). 97 */ 98 src += length; 99 dst += length; 100 t = (long)src; 101 if ((t | (long)dst) & wmask) { 102 if ((t ^ (long)dst) & wmask || length <= wsize) 103 t = length; 104 else 105 t &= wmask; 106 length -= t; 107 TLOOP1(*--dst = *--src); 108 } 109 t = length / wsize; 110 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src); 111 t = length & wmask; 112 TLOOP(*--dst = *--src); 113 } 114 done: 115 return; 116 } 117