lib/libc/string/bcopy.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#)bcopy.c  8.1 (Berkeley) 6/4/93
  37  * $FreeBSD: src/lib/libc/string/bcopy.c,v 1.1.1.1.14.1 2001/07/09 23:30:03 obrien Exp $
  38  * $DragonFly: src/lib/libc/string/bcopy.c,v 1.4 2005/09/18 16:32:34 asmodai Exp $
  39  */
  40
  41 #include <sys/cdefs.h>
  42 #include <string.h>
  43
  44 /*
  45  * sizeof(word) MUST BE A POWER OF TWO
  46  * SO THAT wmask BELOW IS ALL ONES
  47  */
  48 typedef int word;               /* "word" used for optimal copy speed */
  49
  50 #define wsize   sizeof(word)
  51 #define wmask   (wsize - 1)
  52
  53 /*
  54  * Copy a block of memory, handling overlap.
  55  * This is the routine that actually implements
  56  * (the portable versions of) bcopy, memcpy, and memmove.
  57  */
  58 #ifdef MEMCOPY
  59 void *
  60 memcpy(void *dst0, const void *src0, size_t length)
  61 #else
  62 #ifdef MEMMOVE
  63 void *
  64 memmove(void *dst0, const void *src0, size_t length)
  65 #else
  66 void
  67 bcopy(const void *src0, void *dst0, size_t length)
  68 #endif
  69 #endif
  70 {
  71         char *dst = dst0;
  72         const char *src = src0;
  73         size_t t;
  74
  75         if (length == 0 || dst == src)          /* nothing to do */
  76                 goto done;
  77
  78         /*
  79          * Macros: loop-t-times; and loop-t-times, t>0
  80          */
  81 #define TLOOP(s) if (t) TLOOP1(s)
  82 #define TLOOP1(s) do { s; } while (--t)
  83
  84         if ((unsigned long)dst < (unsigned long)src) {
  85                 /*
  86                  * Copy forward.
  87                  */
  88                 t = (int)src;   /* only need low bits */
  89                 if ((t | (int)dst) & wmask) {
  90                         /*
  91                          * Try to align operands.  This cannot be done
  92                          * unless the low bits match.
  93                          */
  94                         if ((t ^ (int)dst) & wmask || length < wsize)
  95                                 t = length;
  96                         else
  97                                 t = wsize - (t & wmask);
  98                         length -= t;
  99                         TLOOP1(*dst++ = *src++);
 100                 }
 101                 /*
 102                  * Copy whole words, then mop up any trailing bytes.
 103                  */
 104                 t = length / wsize;
 105                 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
 106                 t = length & wmask;
 107                 TLOOP(*dst++ = *src++);
 108         } else {
 109                 /*
 110                  * Copy backwards.  Otherwise essentially the same.
 111                  * Alignment works as before, except that it takes
 112                  * (t&wmask) bytes to align, not wsize-(t&wmask).
 113                  */
 114                 src += length;
 115                 dst += length;
 116                 t = (int)src;
 117                 if ((t | (int)dst) & wmask) {
 118                         if ((t ^ (int)dst) & wmask || length <= wsize)
 119                                 t = length;
 120                         else
 121                                 t &= wmask;
 122                         length -= t;
 123                         TLOOP1(*--dst = *--src);
 124                 }
 125                 t = length / wsize;
 126                 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
 127                 t = length & wmask;
 128                 TLOOP(*--dst = *--src);
 129         }
 130 done:
 131 #if defined(MEMCOPY) || defined(MEMMOVE)
 132         return (dst0);
 133 #else
 134         return;
 135 #endif
 136 }