memset.c revision 35923 
1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Mike Hibler and Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#if defined(LIBC_SCCS) && !defined(lint)
38static char sccsid[] = "@(#)memset.c	8.1 (Berkeley) 6/4/93";
39#endif /* LIBC_SCCS and not lint */
40
41#include <sys/types.h>
42
43#include <limits.h>
44#include <string.h>
45
46#define	wsize	sizeof(u_int)
47#define	wmask	(wsize - 1)
48
49#ifdef BZERO
50#define	RETURN	return
51#define	VAL	0
52#define	WIDEVAL	0
53
54void
55bzero(dst0, length)
56	void *dst0;
57	register size_t length;
58#else
59#define	RETURN	return (dst0)
60#define	VAL	c0
61#define	WIDEVAL	c
62
63void *
64memset(dst0, c0, length)
65	void *dst0;
66	register int c0;
67	register size_t length;
68#endif
69{
70	register size_t t;
71	register u_int c;
72	register u_char *dst;
73
74	dst = dst0;
75	/*
76	 * If not enough words, just fill bytes.  A length >= 2 words
77	 * guarantees that at least one of them is `complete' after
78	 * any necessary alignment.  For instance:
79	 *
80	 *	|-----------|-----------|-----------|
81	 *	|00|01|02|03|04|05|06|07|08|09|0A|00|
82	 *	          ^---------------------^
83	 *		 dst		 dst+length-1
84	 *
85	 * but we use a minimum of 3 here since the overhead of the code
86	 * to do word writes is substantial.
87	 */
88	if (length < 3 * wsize) {
89		while (length != 0) {
90			*dst++ = VAL;
91			--length;
92		}
93		RETURN;
94	}
95
96#ifndef BZERO
97	if ((c = (u_char)c0) != 0) {	/* Fill the word. */
98		c = (c << 8) | c;	/* u_int is 16 bits. */
99#if UINT_MAX > 0xffff
100		c = (c << 16) | c;	/* u_int is 32 bits. */
101#endif
102#if UINT_MAX > 0xffffffff
103		c = (c << 32) | c;	/* u_int is 64 bits. */
104#endif
105	}
106#endif
107	/* Align destination by filling in bytes. */
108	if ((t = (long)dst & wmask) != 0) {
109		t = wsize - t;
110		length -= t;
111		do {
112			*dst++ = VAL;
113		} while (--t != 0);
114	}
115
116	/* Fill words.  Length was >= 2*words so we know t >= 1 here. */
117	t = length / wsize;
118	do {
119		*(u_int *)dst = WIDEVAL;
120		dst += wsize;
121	} while (--t != 0);
122
123	/* Mop up trailing bytes, if any. */
124	t = length & wmask;
125	if (t != 0)
126		do {
127			*dst++ = VAL;
128		} while (--t != 0);
129	RETURN;
130}
131