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/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include <sys/types.h> 42 43 #include <limits.h> 44 45 #define wsize sizeof(u_long) 46 #define wmask (wsize - 1) 47 48 #ifdef BZERO 49 #include <strings.h> 50 51 #define RETURN return 52 #define VAL 0 53 #define WIDEVAL 0 54 55 void 56 bzero(void *dst0, size_t length) 57 #else 58 #include <string.h> 59 60 #define RETURN return (dst0) 61 #define VAL c0 62 #define WIDEVAL c 63 64 void * 65 memset(void *dst0, int c0, size_t length) 66 #endif 67 { 68 size_t t; 69 #ifndef BZERO 70 u_long c; 71 #endif 72 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 * TODO: This threshold might not be sensible for 64-bit u_long. 89 * We should benchmark and revisit this decision. 90 */ 91 if (length < 3 * wsize) { 92 while (length != 0) { 93 *dst++ = VAL; 94 --length; 95 } 96 RETURN; 97 } 98 99 #ifndef BZERO 100 if ((c = (u_char)c0) != 0) { /* Fill the word. */ 101 c = (c << 8) | c; /* u_long is 16 bits. */ 102 #if ULONG_MAX > 0xffff 103 c = (c << 16) | c; /* u_long is 32 bits. */ 104 #endif 105 #if ULONG_MAX > 0xffffffff 106 c = (c << 32) | c; /* u_long is 64 bits. */ 107 #endif 108 } 109 #endif 110 /* Align destination by filling in bytes. */ 111 if ((t = (long)dst & wmask) != 0) { 112 t = wsize - t; 113 length -= t; 114 do { 115 *dst++ = VAL; 116 } while (--t != 0); 117 } 118 119 /* Fill words. Length was >= 2*words so we know t >= 1 here. */ 120 t = length / wsize; 121 do { 122 *(u_long *)(void *)dst = WIDEVAL; 123 dst += wsize; 124 } while (--t != 0); 125 126 /* Mop up trailing bytes, if any. */ 127 t = length & wmask; 128 if (t != 0) 129 do { 130 *dst++ = VAL; 131 } while (--t != 0); 132 RETURN; 133 } 134