libsyscall/wrappers/string/memcpy.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 "string.h"
  34
  35 /*
  36  * sizeof(word) MUST BE A POWER OF TWO
  37  * SO THAT wmask BELOW IS ALL ONES
  38  */
  39 typedef int word;               /* "word" used for optimal copy speed */
  40
  41 #define wsize   sizeof(word)
  42 #define wmask   (wsize - 1)
  43
  44 /*
  45  * Copy a block of memory, handling overlap.
  46  * This is the routine that actually implements
  47  * (the portable versions of) bcopy, memcpy, and memmove.
  48  */
  49
  50 __attribute__((visibility("hidden")))
  51 void * memcpy(void *dst0, const void *src0, size_t length)
  52 {
  53         char *dst = dst0;
  54         const char *src = src0;
  55         size_t t;
  56
  57         if (length == 0 || dst == src)          /* nothing to do */
  58                 goto done;
  59
  60         /*
  61          * Macros: loop-t-times; and loop-t-times, t>0
  62          */
  63 #define TLOOP(s) if (t) TLOOP1(s)
  64 #define TLOOP1(s) do { s; } while (--t)
  65
  66         if ((unsigned long)dst < (unsigned long)src) {
  67                 /*
  68                  * Copy forward.
  69                  */
  70                 t = (uintptr_t)src;     /* only need low bits */
  71                 if ((t | (uintptr_t)dst) & wmask) {
  72                         /*
  73                          * Try to align operands.  This cannot be done
  74                          * unless the low bits match.
  75                          */
  76                         if ((t ^ (uintptr_t)dst) & wmask || length < wsize)
  77                                 t = length;
  78                         else
  79                                 t = wsize - (t & wmask);
  80                         length -= t;
  81                         TLOOP1(*dst++ = *src++);
  82                 }
  83                 /*
  84                  * Copy whole words, then mop up any trailing bytes.
  85                  */
  86                 t = length / wsize;
  87                 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
  88                 t = length & wmask;
  89                 TLOOP(*dst++ = *src++);
  90         } else {
  91                 /*
  92                  * Copy backwards.  Otherwise essentially the same.
  93                  * Alignment works as before, except that it takes
  94                  * (t&wmask) bytes to align, not wsize-(t&wmask).
  95                  */
  96                 src += length;
  97                 dst += length;
  98                 t = (uintptr_t)src;
  99                 if ((t | (uintptr_t)dst) & wmask) {
 100                         if ((t ^ (uintptr_t)dst) & wmask || length <= wsize)
 101                                 t = length;
 102                         else
 103                                 t &= wmask;
 104                         length -= t;
 105                         TLOOP1(*--dst = *--src);
 106                 }
 107                 t = length / wsize;
 108                 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
 109                 t = length & wmask;
 110                 TLOOP(*--dst = *--src);
 111         }
 112 done:
 113         return (dst0);
 114 }
 115
 116 __attribute__((visibility("hidden")))
 117 void *
 118 memmove(void *s1, const void *s2, size_t n)
 119 {
 120         return memcpy(s1, s2, n);
 121 }
 122
 123 __attribute__((visibility("hidden")))
 124 void
 125 bcopy(const void *s1, void *s2, size_t n)
 126 {
 127         memcpy(s2, s1, n);
 128 }