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memset.c revision 1.1 
      1 /*	$NetBSD: memset.c,v 1.1 2005/12/20 19:28:52 christos 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  * Mike Hibler and 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[] = "@(#)memset.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 __RCSID("$NetBSD: memset.c,v 1.1 2005/12/20 19:28:52 christos Exp $");
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <sys/types.h>
     45 
     46 #if !defined(_KERNEL) && !defined(_STANDALONE)
     47 #include <assert.h>
     48 #include <limits.h>
     49 #include <string.h>
     50 #else
     51 #include <lib/libkern/libkern.h>
     52 #include <machine/limits.h>
     53 #endif
     54 
     55 #define	wsize	sizeof(u_int)
     56 #define	wmask	(wsize - 1)
     57 
     58 #ifdef BZERO
     59 #define	RETURN	return
     60 #define	VAL	0
     61 #define	WIDEVAL	0
     62 
     63 void
     64 bzero(dst0, length)
     65 	void *dst0;
     66 	size_t length;
     67 #else
     68 #define	RETURN	return (dst0)
     69 #define	VAL	c0
     70 #define	WIDEVAL	c
     71 
     72 void *
     73 memset(dst0, c0, length)
     74 	void *dst0;
     75 	int c0;
     76 	size_t length;
     77 #endif
     78 {
     79 	size_t t;
     80 #ifndef BZERO
     81 	u_int c;
     82 #endif
     83 	u_char *dst;
     84 
     85 	_DIAGASSERT(dst0 != 0);
     86 
     87 	dst = dst0;
     88 	/*
     89 	 * If not enough words, just fill bytes.  A length >= 2 words
     90 	 * guarantees that at least one of them is `complete' after
     91 	 * any necessary alignment.  For instance:
     92 	 *
     93 	 *	|-----------|-----------|-----------|
     94 	 *	|00|01|02|03|04|05|06|07|08|09|0A|00|
     95 	 *	          ^---------------------^
     96 	 *		 dst		 dst+length-1
     97 	 *
     98 	 * but we use a minimum of 3 here since the overhead of the code
     99 	 * to do word writes is substantial.
    100 	 */
    101 	if (length < 3 * wsize) {
    102 		while (length != 0) {
    103 			*dst++ = VAL;
    104 			--length;
    105 		}
    106 		RETURN;
    107 	}
    108 
    109 #ifndef BZERO
    110 	if ((c = (u_char)c0) != 0) {	/* Fill the word. */
    111 		c = (c << 8) | c;	/* u_int is 16 bits. */
    112 #if UINT_MAX > 0xffff
    113 		c = (c << 16) | c;	/* u_int is 32 bits. */
    114 #endif
    115 #if UINT_MAX > 0xffffffff
    116 		c = (c << 32) | c;	/* u_int is 64 bits. */
    117 #endif
    118 	}
    119 #endif
    120 	/* Align destination by filling in bytes. */
    121 	if ((t = (size_t)((u_long)dst & wmask)) != 0) {
    122 		t = wsize - t;
    123 		length -= t;
    124 		do {
    125 			*dst++ = VAL;
    126 		} while (--t != 0);
    127 	}
    128 
    129 	/* Fill words.  Length was >= 2*words so we know t >= 1 here. */
    130 	t = length / wsize;
    131 	do {
    132 		*(u_int *)(void *)dst = WIDEVAL;
    133 		dst += wsize;
    134 	} while (--t != 0);
    135 
    136 	/* Mop up trailing bytes, if any. */
    137 	t = length & wmask;
    138 	if (t != 0)
    139 		do {
    140 			*dst++ = VAL;
    141 		} while (--t != 0);
    142 	RETURN;
    143 }
    144