memset.c revision 77117 
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#ifndef lint
41static const char rcsid[] =
42  "$FreeBSD: head/lib/libc/string/memset.c 77117 2001-05-24 08:47:42Z obrien $";
43#endif
44
45#include <sys/types.h>
46
47#include <limits.h>
48#include <string.h>
49
50#define	wsize	sizeof(u_int)
51#define	wmask	(wsize - 1)
52
53#ifdef BZERO
54#define	RETURN	return
55#define	VAL	0
56#define	WIDEVAL	0
57
58void
59bzero(dst0, length)
60	void *dst0;
61	register size_t length;
62#else
63#define	RETURN	return (dst0)
64#define	VAL	c0
65#define	WIDEVAL	c
66
67void *
68memset(dst0, c0, length)
69	void *dst0;
70	register int c0;
71	register size_t length;
72#endif
73{
74	register size_t t;
75#ifndef BZERO
76	register u_int c;
77#endif
78	register u_char *dst;
79
80	dst = dst0;
81	/*
82	 * If not enough words, just fill bytes.  A length >= 2 words
83	 * guarantees that at least one of them is `complete' after
84	 * any necessary alignment.  For instance:
85	 *
86	 *	|-----------|-----------|-----------|
87	 *	|00|01|02|03|04|05|06|07|08|09|0A|00|
88	 *	          ^---------------------^
89	 *		 dst		 dst+length-1
90	 *
91	 * but we use a minimum of 3 here since the overhead of the code
92	 * to do word writes is substantial.
93	 */
94	if (length < 3 * wsize) {
95		while (length != 0) {
96			*dst++ = VAL;
97			--length;
98		}
99		RETURN;
100	}
101
102#ifndef BZERO
103	if ((c = (u_char)c0) != 0) {	/* Fill the word. */
104		c = (c << 8) | c;	/* u_int is 16 bits. */
105#if UINT_MAX > 0xffff
106		c = (c << 16) | c;	/* u_int is 32 bits. */
107#endif
108#if UINT_MAX > 0xffffffff
109		c = (c << 32) | c;	/* u_int is 64 bits. */
110#endif
111	}
112#endif
113	/* Align destination by filling in bytes. */
114	if ((t = (long)dst & wmask) != 0) {
115		t = wsize - t;
116		length -= t;
117		do {
118			*dst++ = VAL;
119		} while (--t != 0);
120	}
121
122	/* Fill words.  Length was >= 2*words so we know t >= 1 here. */
123	t = length / wsize;
124	do {
125		*(u_int *)dst = WIDEVAL;
126		dst += wsize;
127	} while (--t != 0);
128
129	/* Mop up trailing bytes, if any. */
130	t = length & wmask;
131	if (t != 0)
132		do {
133			*dst++ = VAL;
134		} while (--t != 0);
135	RETURN;
136}
137