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