1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
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 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)memset.c 8.1 (Berkeley) 6/4/93";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/types.h>
39
40 #include <limits.h>
41
42 #define wsize sizeof(u_long)
43 #define wmask (wsize - 1)
44
45 #ifdef BZERO
46 #include <strings.h>
47
48 #define RETURN return
49 #define VAL 0
50 #define WIDEVAL 0
51
52 void
bzero(void * dst0,size_t length)53 bzero(void *dst0, size_t length)
54 #else
55 #include <string.h>
56
57 #define RETURN return (dst0)
58 #define VAL c0
59 #define WIDEVAL c
60
61 void *
62 memset(void *dst0, int c0, size_t length)
63 #endif
64 {
65 size_t t;
66 #ifndef BZERO
67 u_long c;
68 #endif
69 u_char *dst;
70
71 dst = dst0;
72 /*
73 * If not enough words, just fill bytes. A length >= 2 words
74 * guarantees that at least one of them is `complete' after
75 * any necessary alignment. For instance:
76 *
77 * |-----------|-----------|-----------|
78 * |00|01|02|03|04|05|06|07|08|09|0A|00|
79 * ^---------------------^
80 * dst dst+length-1
81 *
82 * but we use a minimum of 3 here since the overhead of the code
83 * to do word writes is substantial.
84 *
85 * TODO: This threshold might not be sensible for 64-bit u_long.
86 * We should benchmark and revisit this decision.
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_long is 16 bits. */
99 #if ULONG_MAX > 0xffff
100 c = (c << 16) | c; /* u_long is 32 bits. */
101 #endif
102 #if ULONG_MAX > 0xffffffff
103 c = (c << 32) | c; /* u_long 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_long *)(void *)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