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 *
  52 _libkernel_memmove(void *dst0, const void *src0, size_t length)
  53 {
  54         char *dst = dst0;
  55         const char *src = src0;
  56         size_t t;
  57
  58         if (length == 0 || dst == src) {        /* nothing to do */
  59                 goto done;
  60         }
  61
  62         /*
  63          * Macros: loop-t-times; and loop-t-times, t>0
  64          */
  65 #define TLOOP(s) if (t) TLOOP1(s)
  66 #define TLOOP1(s) do { s; } while (--t)
  67
  68         if ((unsigned long)dst < (unsigned long)src) {
  69                 /*
  70                  * Copy forward.
  71                  */
  72                 t = (uintptr_t)src;     /* only need low bits */
  73                 if ((t | (uintptr_t)dst) & wmask) {
  74                         /*
  75                          * Try to align operands.  This cannot be done
  76                          * unless the low bits match.
  77                          */
  78                         if ((t ^ (uintptr_t)dst) & wmask || length < wsize) {
  79                                 t = length;
  80                         } else {
  81                                 t = wsize - (t & wmask);
  82                         }
  83                         length -= t;
  84                         TLOOP1(*dst++ = *src++);
  85                 }
  86                 /*
  87                  * Copy whole words, then mop up any trailing bytes.
  88                  */
  89                 t = length / wsize;
  90                 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
  91                 t = length & wmask;
  92                 TLOOP(*dst++ = *src++);
  93         } else {
  94                 /*
  95                  * Copy backwards.  Otherwise essentially the same.
  96                  * Alignment works as before, except that it takes
  97                  * (t&wmask) bytes to align, not wsize-(t&wmask).
  98                  */
  99                 src += length;
 100                 dst += length;
 101                 t = (uintptr_t)src;
 102                 if ((t | (uintptr_t)dst) & wmask) {
 103                         if ((t ^ (uintptr_t)dst) & wmask || length <= wsize) {
 104                                 t = length;
 105                         } else {
 106                                 t &= wmask;
 107                         }
 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 __attribute__((visibility("hidden")))
 121 void
 122 bcopy(const void *s1, void *s2, size_t n)
 123 {
 124         memcpy(s2, s1, n);
 125 }