FreeBSD/Linux Kernel Cross Reference
sys/lib/libkern/bcopy.c

     /*      $NetBSD: bcopy.c,v 1.5 2003/08/07 16:32:07 agc Exp $    */
     
     /*-
      * Copyright (c) 1990, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * Chris Torek.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    #if defined(LIBC_SCCS) && !defined(lint)
    #if 0
    static char sccsid[] = "@(#)bcopy.c     8.1 (Berkeley) 6/4/93";
    #else
    __RCSID("$NetBSD: bcopy.c,v 1.5 2003/08/07 16:32:07 agc Exp $");
    #endif
    #endif /* LIBC_SCCS and not lint */
    
    #if !defined(_KERNEL) && !defined(_STANDALONE)
    #include <string.h>
    #else
    #include <lib/libkern/libkern.h>
    #endif
    
    /*
     * sizeof(word) MUST BE A POWER OF TWO
     * SO THAT wmask BELOW IS ALL ONES
     */
    typedef long word;              /* "word" used for optimal copy speed */
    
    #define wsize   sizeof(word)
    #define wmask   (wsize - 1)
    
    /*
     * Copy a block of memory, handling overlap.
     * This is the routine that actually implements
     * (the portable versions of) bcopy, memcpy, and memmove.
     */
    #ifdef MEMCOPY
    void *
    memcpy(dst0, src0, length)
    #else
    #ifdef MEMMOVE
    void *
    memmove(dst0, src0, length)
    #else
    void
    bcopy(src0, dst0, length)
    #endif
    #endif
            void *dst0;
            const void *src0;
            size_t length;
    {
            char *dst = dst0;
            const char *src = src0;
            size_t t;
    
            if (length == 0 || dst == src)          /* nothing to do */
                    goto done;
    
            /*
             * Macros: loop-t-times; and loop-t-times, t>0
             */
    #define TLOOP(s) if (t) TLOOP1(s)
    #define TLOOP1(s) do { s; } while (--t)
    
    #ifndef MEMCOPY
            if ((unsigned long)dst < (unsigned long)src) {
    #endif
                    /*
                     * Copy forward.
                     */
                    t = (long)src;  /* only need low bits */
                   if ((t | (long)dst) & wmask) {
                           /*
                            * Try to align operands.  This cannot be done
                            * unless the low bits match.
                            */
                           if ((t ^ (long)dst) & wmask || length < wsize)
                                   t = length;
                           else
                                   t = wsize - (t & wmask);
                           length -= t;
                           TLOOP1(*dst++ = *src++);
                   }
                   /*
                    * Copy whole words, then mop up any trailing bytes.
                    */
                   t = length / wsize;
                   TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
                   t = length & wmask;
                   TLOOP(*dst++ = *src++);
   #ifndef MEMCOPY
           } else {
                   /*
                    * Copy backwards.  Otherwise essentially the same.
                    * Alignment works as before, except that it takes
                    * (t&wmask) bytes to align, not wsize-(t&wmask).
                    */
                   src += length;
                   dst += length;
                   t = (long)src;
                   if ((t | (long)dst) & wmask) {
                           if ((t ^ (long)dst) & wmask || length <= wsize)
                                   t = length;
                           else
                                   t &= wmask;
                           length -= t;
                           TLOOP1(*--dst = *--src);
                   }
                   t = length / wsize;
                   TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
                   t = length & wmask;
                   TLOOP(*--dst = *--src);
           }
   #endif  /* MEMCOPY */
   
   done:
   #if defined(MEMCOPY) || defined(MEMMOVE)
           return (dst0);
   #else
           return;
   #endif
   }

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