memset.c revision 86170 
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#include <sys/cdefs.h>
41__FBSDID("$FreeBSD: head/lib/libc/string/memset.c 86170 2001-11-07 19:55:16Z obrien $");
42
43#include <sys/types.h>
44
45#include <limits.h>
46#include <string.h>
47
48#define	wsize	sizeof(u_int)
49#define	wmask	(wsize - 1)
50
51#ifdef BZERO
52#define	RETURN	return
53#define	VAL	0
54#define	WIDEVAL	0
55
56void
57bzero(dst0, length)
58	void *dst0;
59	register size_t length;
60#else
61#define	RETURN	return (dst0)
62#define	VAL	c0
63#define	WIDEVAL	c
64
65void *
66memset(dst0, c0, length)
67	void *dst0;
68	register int c0;
69	register size_t length;
70#endif
71{
72	register size_t t;
73#ifndef BZERO
74	register u_int c;
75#endif
76	register u_char *dst;
77
78	dst = dst0;
79	/*
80	 * If not enough words, just fill bytes.  A length >= 2 words
81	 * guarantees that at least one of them is `complete' after
82	 * any necessary alignment.  For instance:
83	 *
84	 *	|-----------|-----------|-----------|
85	 *	|00|01|02|03|04|05|06|07|08|09|0A|00|
86	 *	          ^---------------------^
87	 *		 dst		 dst+length-1
88	 *
89	 * but we use a minimum of 3 here since the overhead of the code
90	 * to do word writes is substantial.
91	 */
92	if (length < 3 * wsize) {
93		while (length != 0) {
94			*dst++ = VAL;
95			--length;
96		}
97		RETURN;
98	}
99
100#ifndef BZERO
101	if ((c = (u_char)c0) != 0) {	/* Fill the word. */
102		c = (c << 8) | c;	/* u_int is 16 bits. */
103#if UINT_MAX > 0xffff
104		c = (c << 16) | c;	/* u_int is 32 bits. */
105#endif
106#if UINT_MAX > 0xffffffff
107		c = (c << 32) | c;	/* u_int is 64 bits. */
108#endif
109	}
110#endif
111	/* Align destination by filling in bytes. */
112	if ((t = (long)dst & wmask) != 0) {
113		t = wsize - t;
114		length -= t;
115		do {
116			*dst++ = VAL;
117		} while (--t != 0);
118	}
119
120	/* Fill words.  Length was >= 2*words so we know t >= 1 here. */
121	t = length / wsize;
122	do {
123		*(u_int *)dst = WIDEVAL;
124		dst += wsize;
125	} while (--t != 0);
126
127	/* Mop up trailing bytes, if any. */
128	t = length & wmask;
129	if (t != 0)
130		do {
131			*dst++ = VAL;
132		} while (--t != 0);
133	RETURN;
134}
135