gonzui

    1: /*      $OpenBSD: bcopy.c,v 1.5 2005/08/08 08:05:37 espie Exp $ */
    2: /*-
    3:  * Copyright (c) 1990 The Regents of the University of California.
    4:  * All rights reserved.
    5:  *
    6:  * This code is derived from software contributed to Berkeley by
    7:  * Chris Torek.
    8:  *
    9:  * Redistribution and use in source and binary forms, with or without
   10:  * modification, are permitted provided that the following conditions
   11:  * are met:
   12:  * 1. Redistributions of source code must retain the above copyright
   13:  *    notice, this list of conditions and the following disclaimer.
   14:  * 2. Redistributions in binary form must reproduce the above copyright
   15:  *    notice, this list of conditions and the following disclaimer in the
   16:  *    documentation and/or other materials provided with the distribution.
   17:  * 3. Neither the name of the University nor the names of its contributors
   18:  *    may be used to endorse or promote products derived from this software
   19:  *    without specific prior written permission.
   20:  *
   21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31:  * SUCH DAMAGE.
   32:  */
   33: 
   34: #include <string.h>
   35: 
   36: /*
   37:  * sizeof(word) MUST BE A POWER OF TWO
   38:  * SO THAT wmask BELOW IS ALL ONES
   39:  */
   40: typedef long word;              /* "word" used for optimal copy speed */
   41: 
   42: #define wsize   sizeof(word)
   43: #define wmask   (wsize - 1)
   44: #define MEMCOPY
   45: /*
   46:  * Copy a block of memory, handling overlap.
   47:  * This is the routine that actually implements
   48:  * (the portable versions of) bcopy, memcpy, and memmove.
   49:  */
   50: #ifdef MEMCOPY
   51: void *
   52: memcpy(void *dst0, const void *src0, size_t length)
   53: #else
   54: #ifdef MEMMOVE
   55: void *
   56: memmove(void *dst0, const void *src0, size_t length)
   57: #else
   58: void
   59: bcopy(const void *src0, void *dst0, size_t length)
   60: #endif
   61: #endif
   62: {
   63:         char *dst = dst0;
   64:         const char *src = src0;
   65:         size_t t;
   66: 
   67:         if (length == 0 || dst == src)         /* nothing to do */
   68:                 goto done;
   69: 
   70:         /*
   71:          * Macros: loop-t-times; and loop-t-times, t>0
   72:          */
   73: #define TLOOP(s) if (t) TLOOP1(s)
   74: #define TLOOP1(s) do { s; } while (--t)
   75: 
   76:         if ((unsigned long)dst < (unsigned long)src) {
   77:                 /*
   78:                  * Copy forward.
   79:                  */
   80:                 t = (long)src;        /* only need low bits */
   81:                 if ((t | (long)dst) & wmask) {
   82:                         /*
   83:                          * Try to align operands.  This cannot be done
   84:                          * unless the low bits match.
   85:                          */
   86:                         if ((t ^ (long)dst) & wmask || length < wsize)
   87:                                 t = length;
   88:                         else
   89:                                 t = wsize - (t & wmask);
   90:                         length -= t;
   91:                         TLOOP1(*dst++ = *src++);
   92:                 }
   93:                 /*
   94:                  * Copy whole words, then mop up any trailing bytes.
   95:                  */
   96:                 t = length / wsize;
   97:                 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
   98:                 t = length & wmask;
   99:                 TLOOP(*dst++ = *src++);
  100:         } else {
  101:                 /*
  102:                  * Copy backwards.  Otherwise essentially the same.
  103:                  * Alignment works as before, except that it takes
  104:                  * (t&wmask) bytes to align, not wsize-(t&wmask).
  105:                  */
  106:                 src += length;
  107:                 dst += length;
  108:                 t = (long)src;
  109:                 if ((t | (long)dst) & wmask) {
  110:                         if ((t ^ (long)dst) & wmask || length <= wsize)
  111:                                 t = length;
  112:                         else
  113:                                 t &= wmask;
  114:                         length -= t;
  115:                         TLOOP1(*--dst = *--src);
  116:                 }
  117:                 t = length / wsize;
  118:                 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
  119:                 t = length & wmask;
  120:                 TLOOP(*--dst = *--src);
  121:         }
  122: done:
  123: #if defined(MEMCOPY) || defined(MEMMOVE)
  124:         return (dst0);
  125: #else
  126:         return;
  127: #endif
  128: }
  129: __weak_alias(memmove, memcpy);
  130: __weak_alias(bcopy, memcpy);