text: /*	$OpenBSD: memset.c,v 1.6 2009/10/27 23:59:35 deraadt Exp $	*/
  /*	$NetBSD: memset.c,v 1.6 1998/03/27 05:35:47 cgd 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
   * Mike Hibler and 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/types.h>
  
  #if !defined(_KERNEL) && !defined(_STANDALONE)
  #include <string.h>
  #include <limits.h>
  #else
  #include <sys/limits.h>
  #include <sys/systm.h>
  #include <lib/libkern/libkern.h>
  #endif 
  
  #define	wsize	sizeof(u_int)
  #define	wmask	(wsize - 1)
  
  #ifdef BZERO
  #define	RETURN	return
  #define	VAL	0
  #define	WIDEVAL	0
  
  void
  bzero(void *dst0, size_t length)
  #else
  #define	RETURN	return (dst0)
  #define	VAL	c0
  #define	WIDEVAL	c
  
  void *
  memset(void *dst0, int c0, size_t length)
  #endif
  {
  	size_t t;
  #ifndef BZERO
  	u_int c;
  #endif
  	u_char *dst;
  
  	dst = dst0;
  	/*
  	 * If not enough words, just fill bytes.  A length >= 2 words
  	 * guarantees that at least one of them is `complete' after
  	 * any necessary alignment.  For instance:
  	 *
  	 *	|-----------|-----------|-----------|
  	 *	|00|01|02|03|04|05|06|07|08|09|0A|00|
  	 *	          ^---------------------^
  	 *		 dst		 dst+length-1
  	 *
  	 * but we use a minimum of 3 here since the overhead of the code
  	 * to do word writes is substantial.
  	 */ 
  	if (length < 3 * wsize) {
  		while (length != 0) {
  			*dst++ = VAL;
  			--length;
  		}
  		RETURN;
  	}
  
  #ifndef BZERO
  	if ((c = (u_char)c0) != 0) {	/* Fill the word. */
  		c = (c << 8) | c;	/* u_int is 16 bits. */
  #if UINT_MAX > 0xffff
  		c = (c << 16) | c;	/* u_int is 32 bits. */
  #endif
  #if UINT_MAX > 0xffffffff
  		c = (c << 32) | c;	/* u_int is 64 bits. */
  #endif
  	}
  #endif
  	/* Align destination by filling in bytes. */
  	if ((t = (u_long)dst & wmask) != 0) {
  		t = wsize - t;
  		length -= t;
  		do {
  			*dst++ = VAL;
  		} while (--t != 0);
  	}
  
  	/* Fill words.  Length was >= 2*words so we know t >= 1 here. */
  	t = length / wsize;
  	do {
  		*(u_int *)dst = WIDEVAL;
  		dst += wsize;
  	} while (--t != 0);
  
  	/* Mop up trailing bytes, if any. */
  	t = length & wmask;
  	if (t != 0)
  		do {
  			*dst++ = VAL;
  		} while (--t != 0);
  	RETURN;
  }
  