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bcopy.c revision 1.2 
      1 /*	$NetBSD: bcopy.c,v 1.2 2006/02/05 06:47:48 ross Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Chris Torek.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)bcopy.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 __RCSID("$NetBSD: bcopy.c,v 1.2 2006/02/05 06:47:48 ross Exp $");
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #if !defined(_KERNEL) && !defined(_STANDALONE)
     45 #include <assert.h>
     46 #include <string.h>
     47 #else
     48 #include <lib/libkern/libkern.h>
     49 #endif
     50 
     51 /*
     52  * sizeof(word) MUST BE A POWER OF TWO
     53  * SO THAT wmask BELOW IS ALL ONES
     54  */
     55 typedef	long word;		/* "word" used for optimal copy speed */
     56 
     57 #define	wsize	sizeof(word)
     58 #define	wmask	(wsize - 1)
     59 
     60 /*
     61  * Copy a block of memory, handling overlap.
     62  * This is the routine that actually implements
     63  * (the portable versions of) bcopy, memcpy, and memmove.
     64  */
     65 #ifdef MEMCOPY
     66 void *
     67 memcpy(dst0, src0, length)
     68 #else
     69 #ifdef MEMMOVE
     70 void *
     71 memmove(dst0, src0, length)
     72 #else
     73 void
     74 bcopy(src0, dst0, length)
     75 #endif
     76 #endif
     77 	void *dst0;
     78 	const void *src0;
     79 	size_t length;
     80 {
     81 	char *dst = dst0;
     82 	const char *src = src0;
     83 	size_t t;
     84 	unsigned long u;
     85 
     86 #if !defined(_KERNEL)
     87 	_DIAGASSERT(dst0 != 0);
     88 	_DIAGASSERT(src0 != 0);
     89 #endif
     90 
     91 	if (length == 0 || dst == src)		/* nothing to do */
     92 		goto done;
     93 
     94 	/*
     95 	 * Macros: loop-t-times; and loop-t-times, t>0
     96 	 */
     97 #define	TLOOP(s) if (t) TLOOP1(s)
     98 #define	TLOOP1(s) do { s; } while (--t)
     99 
    100 	if ((unsigned long)dst < (unsigned long)src) {
    101 		/*
    102 		 * Copy forward.
    103 		 */
    104 		u = (unsigned long)src;	/* only need low bits */
    105 		if ((u | (unsigned long)dst) & wmask) {
    106 			/*
    107 			 * Try to align operands.  This cannot be done
    108 			 * unless the low bits match.
    109 			 */
    110 			if ((u ^ (unsigned long)dst) & wmask || length < wsize)
    111 				t = length;
    112 			else
    113 				t = wsize - (size_t)(u & wmask);
    114 			length -= t;
    115 			TLOOP1(*dst++ = *src++);
    116 		}
    117 		/*
    118 		 * Copy whole words, then mop up any trailing bytes.
    119 		 */
    120 		t = length / wsize;
    121 		TLOOP(*(word *)(void *)dst = *(const word *)(const void *)src; src += wsize; dst += wsize);
    122 		t = length & wmask;
    123 		TLOOP(*dst++ = *src++);
    124 	} else {
    125 		/*
    126 		 * Copy backwards.  Otherwise essentially the same.
    127 		 * Alignment works as before, except that it takes
    128 		 * (t&wmask) bytes to align, not wsize-(t&wmask).
    129 		 */
    130 		src += length;
    131 		dst += length;
    132 		_DIAGASSERT((unsigned long)dst >= (unsigned long)dst0);
    133 		_DIAGASSERT((unsigned long)src >= (unsigned long)src0);
    134 		u = (unsigned long)src;
    135 		if ((u | (unsigned long)dst) & wmask) {
    136 			if ((u ^ (unsigned long)dst) & wmask || length <= wsize)
    137 				t = length;
    138 			else
    139 				t = (size_t)(u & wmask);
    140 			length -= t;
    141 			TLOOP1(*--dst = *--src);
    142 		}
    143 		t = length / wsize;
    144 		TLOOP(src -= wsize; dst -= wsize; *(word *)(void *)dst = *(const word *)(const void *)src);
    145 		t = length & wmask;
    146 		TLOOP(*--dst = *--src);
    147 	}
    148 done:
    149 #if defined(MEMCOPY) || defined(MEMMOVE)
    150 	return (dst0);
    151 #else
    152 	return;
    153 #endif
    154 }
    155