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. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)bcopy.c  8.1 (Berkeley) 6/4/93
  33  * $FreeBSD: head/lib/libc/string/bcopy.c 251069 2013-05-28 20:57:40Z emaste $
  34  */
  35
  36 #include <sys/types.h>
  37
  38 /*
  39  * sizeof(word) MUST BE A POWER OF TWO
  40  * SO THAT wmask BELOW IS ALL ONES
  41  */
  42 typedef int 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 #if defined(MEMCOPY) || defined(MEMMOVE)
  53 #include <string.h>
  54
  55 void *
  56 #ifdef MEMCOPY
  57 memcpy
  58 #else
  59 memmove
  60 #endif
  61 (void *dst0, const void *src0, size_t length)
  62 #else
  63 #include <strings.h>
  64
  65 void
  66 bcopy(const void *src0, void *dst0, size_t length)
  67 #endif
  68 {
  69         char *dst = dst0;
  70         const char *src = src0;
  71         size_t t;
  72
  73         if (length == 0 || dst == src)          /* nothing to do */
  74                 goto done;
  75
  76         /*
  77          * Macros: loop-t-times; and loop-t-times, t>0
  78          */
  79 #define TLOOP(s) if (t) TLOOP1(s)
  80 #define TLOOP1(s) do { s; } while (--t)
  81
  82         if ((unsigned long)dst < (unsigned long)src) {
  83                 /*
  84                  * Copy forward.
  85                  */
  86                 t = (uintptr_t)src;     /* only need low bits */
  87                 if ((t | (uintptr_t)dst) & wmask) {
  88                         /*
  89                          * Try to align operands.  This cannot be done
  90                          * unless the low bits match.
  91                          */
  92                         if ((t ^ (uintptr_t)dst) & wmask || length < wsize)
  93                                 t = length;
  94                         else
  95                                 t = wsize - (t & wmask);
  96                         length -= t;
  97                         TLOOP1(*dst++ = *src++);
  98                 }
  99                 /*
 100                  * Copy whole words, then mop up any trailing bytes.
 101                  */
 102                 t = length / wsize;
 103                 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
 104                 t = length & wmask;
 105                 TLOOP(*dst++ = *src++);
 106         } else {
 107                 /*
 108                  * Copy backwards.  Otherwise essentially the same.
 109                  * Alignment works as before, except that it takes
 110                  * (t&wmask) bytes to align, not wsize-(t&wmask).
 111                  */
 112                 src += length;
 113                 dst += length;
 114                 t = (uintptr_t)src;
 115                 if ((t | (uintptr_t)dst) & wmask) {
 116                         if ((t ^ (uintptr_t)dst) & wmask || length <= wsize)
 117                                 t = length;
 118                         else
 119                                 t &= wmask;
 120                         length -= t;
 121                         TLOOP1(*--dst = *--src);
 122                 }
 123                 t = length / wsize;
 124                 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
 125                 t = length & wmask;
 126                 TLOOP(*--dst = *--src);
 127         }
 128 done:
 129 #if defined(MEMCOPY) || defined(MEMMOVE)
 130         return (dst0);
 131 #else
 132         return;
 133 #endif
 134 }