src/string/generic/memmove.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  * 4. 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
  33 #include <platform/string.h>
  34
  35 #if !_PLATFORM_OPTIMIZED_MEMMOVE
  36
  37 #include <sys/types.h>
  38
  39 /*
  40  * sizeof(word) MUST BE A POWER OF TWO
  41  * SO THAT wmask BELOW IS ALL ONES
  42  */
  43 typedef long word;              /* "word" used for optimal copy speed */
  44
  45 #define wsize   sizeof(word)
  46 #define wmask   (wsize - 1)
  47
  48 /*
  49  * Copy a block of memory, handling overlap.
  50  * This is the routine that actually implements
  51  * (the portable versions of) bcopy, memcpy, and memmove.
  52  */
  53
  54 void *
  55 _platform_memmove(void *dst0, const void *src0, size_t length)
  56 {
  57         char *dst = dst0;
  58         const char *src = src0;
  59         size_t t;
  60
  61         if (length == 0 || dst == src)          /* nothing to do */
  62                 goto done;
  63
  64         /*
  65          * Macros: loop-t-times; and loop-t-times, t>0
  66          */
  67 #define TLOOP(s) if (t) TLOOP1(s)
  68 #define TLOOP1(s) do { s; } while (--t)
  69
  70         if ((unsigned long)dst < (unsigned long)src) {
  71                 /*
  72                  * Copy forward.
  73                  */
  74                 t = (uintptr_t)src;     /* only need low bits */
  75                 if ((t | (uintptr_t)dst) & wmask) {
  76                         /*
  77                          * Try to align operands.  This cannot be done
  78                          * unless the low bits match.
  79                          */
  80                         if ((t ^ (uintptr_t)dst) & wmask || length < wsize)
  81                                 t = length;
  82                         else
  83                                 t = wsize - (t & wmask);
  84                         length -= t;
  85                         TLOOP1(*dst++ = *src++);
  86                 }
  87                 /*
  88                  * Copy whole words, then mop up any trailing bytes.
  89                  */
  90                 t = length / wsize;
  91                 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
  92                 t = length & wmask;
  93                 TLOOP(*dst++ = *src++);
  94         } else {
  95                 /*
  96                  * Copy backwards.  Otherwise essentially the same.
  97                  * Alignment works as before, except that it takes
  98                  * (t&wmask) bytes to align, not wsize-(t&wmask).
  99                  */
 100                 src += length;
 101                 dst += length;
 102                 t = (uintptr_t)src;
 103                 if ((t | (uintptr_t)dst) & wmask) {
 104                         if ((t ^ (uintptr_t)dst) & wmask || length <= wsize)
 105                                 t = length;
 106                         else
 107                                 t &= wmask;
 108                         length -= t;
 109                         TLOOP1(*--dst = *--src);
 110                 }
 111                 t = length / wsize;
 112                 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
 113                 t = length & wmask;
 114                 TLOOP(*--dst = *--src);
 115         }
 116 done:
 117         return (dst0);
 118 }
 119
 120 #if VARIANT_STATIC
 121 void *
 122 memmove(void *dst0, const void *src0, size_t length)
 123 {
 124         return _platform_memmove(dst0, src0, length);
 125 }
 126
 127 void *
 128 memcpy(void *dst0, const void *src0, size_t length)
 129 {
 130         return _platform_memmove(dst0, src0, length);
 131 }
 132 #endif
 133
 134 #endif