string/FreeBSD/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
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)bcopy.c     8.1 (Berkeley) 6/4/93";
  39 #endif /* LIBC_SCCS and not lint */
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: src/lib/libc/string/bcopy.c,v 1.5 2002/09/01 21:53:46 robert Exp $");
  42
  43 /*
  44  * sizeof(word) MUST BE A POWER OF TWO
  45  * SO THAT wmask BELOW IS ALL ONES
  46  */
  47 typedef int word;               /* "word" used for optimal copy speed */
  48
  49 #define wsize   sizeof(word)
  50 #define wmask   (wsize - 1)
  51
  52 /*
  53  * Copy a block of memory, handling overlap.
  54  * This is the routine that actually implements
  55  * (the portable versions of) bcopy, memcpy, and memmove.
  56  */
  57 #if defined(MEMCOPY) || defined(MEMMOVE)
  58 #include <string.h>
  59
  60 void *
  61 #ifdef MEMCOPY
  62 memcpy
  63 #else
  64 memmove
  65 #endif
  66 (void *dst0, const void *src0, size_t length)
  67 #else
  68 #include <strings.h>
  69
  70 void
  71 bcopy(const void *src0, void *dst0, size_t length)
  72 #endif
  73 {
  74         char *dst = dst0;
  75         const char *src = src0;
  76         size_t t;
  77
  78         if (length == 0 || dst == src)          /* nothing to do */
  79                 goto done;
  80
  81         /*
  82          * Macros: loop-t-times; and loop-t-times, t>0
  83          */
  84 #define TLOOP(s) if (t) TLOOP1(s)
  85 #define TLOOP1(s) do { s; } while (--t)
  86
  87         if ((unsigned long)dst < (unsigned long)src) {
  88                 /*
  89                  * Copy forward.
  90                  */
  91                 t = (int)src;   /* only need low bits */
  92                 if ((t | (int)dst) & wmask) {
  93                         /*
  94                          * Try to align operands.  This cannot be done
  95                          * unless the low bits match.
  96                          */
  97                         if ((t ^ (int)dst) & wmask || length < wsize)
  98                                 t = length;
  99                         else
 100                                 t = wsize - (t & wmask);
 101                         length -= t;
 102                         TLOOP1(*dst++ = *src++);
 103                 }
 104                 /*
 105                  * Copy whole words, then mop up any trailing bytes.
 106                  */
 107                 t = length / wsize;
 108                 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
 109                 t = length & wmask;
 110                 TLOOP(*dst++ = *src++);
 111         } else {
 112                 /*
 113                  * Copy backwards.  Otherwise essentially the same.
 114                  * Alignment works as before, except that it takes
 115                  * (t&wmask) bytes to align, not wsize-(t&wmask).
 116                  */
 117                 src += length;
 118                 dst += length;
 119                 t = (int)src;
 120                 if ((t | (int)dst) & wmask) {
 121                         if ((t ^ (int)dst) & wmask || length <= wsize)
 122                                 t = length;
 123                         else
 124                                 t &= wmask;
 125                         length -= t;
 126                         TLOOP1(*--dst = *--src);
 127                 }
 128                 t = length / wsize;
 129                 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
 130                 t = length & wmask;
 131                 TLOOP(*--dst = *--src);
 132         }
 133 done:
 134 #if defined(MEMCOPY) || defined(MEMMOVE)
 135         return (dst0);
 136 #else
 137         return;
 138 #endif
 139 }