1 // SPDX-License-Identifier: BSD-3-Clause 2 /* 3 * Copyright (c) 1994-2009 Red Hat, Inc. 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions are met: 8 * 9 * 1. Redistributions of source code must retain the above copyright notice, 10 * this list of conditions and the following disclaimer. 11 * 12 * 2. Redistributions in binary form must reproduce the above copyright notice, 13 * this list of conditions and the following disclaimer in the documentation 14 * and/or other materials provided with the distribution. 15 * 16 * 3. Neither the name of the copyright holder nor the names of its 17 * contributors may be used to endorse or promote products derived from this 18 * software without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 21 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 24 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 30 * POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 /* 34 FUNCTION 35 <<memset>>---set an area of memory 36 37 INDEX 38 memset 39 40 ANSI_SYNOPSIS 41 #include <string.h> 42 void *memset(void *<[dst]>, int <[c]>, size_t <[length]>); 43 44 TRAD_SYNOPSIS 45 #include <string.h> 46 void *memset(<[dst]>, <[c]>, <[length]>) 47 void *<[dst]>; 48 int <[c]>; 49 size_t <[length]>; 50 51 DESCRIPTION 52 This function converts the argument <[c]> into an unsigned 53 char and fills the first <[length]> characters of the array 54 pointed to by <[dst]> to the value. 55 56 RETURNS 57 <<memset>> returns the value of <[dst]>. 58 59 PORTABILITY 60 <<memset>> is ANSI C. 61 62 <<memset>> requires no supporting OS subroutines. 63 64 QUICKREF 65 memset ansi pure 66 */ 67 68 #include "_ansi.h" 69 #include <string.h> 70 71 #define LBLOCKSIZE (sizeof(long)) 72 #define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1)) 73 #define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE) 74 75 _PTR _DEFUN(memset, (m, c, n), _PTR m _AND int c _AND size_t n) 76 { 77 char *s = (char *)m; 78 79 #if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__) 80 int i; 81 unsigned long buffer; 82 unsigned long *aligned_addr; 83 unsigned int d = c & 0xff; /* To avoid sign extension, copy C to an 84 unsigned variable. */ 85 86 while (UNALIGNED(s)) { 87 if (n--) 88 *s++ = (char)c; 89 else 90 return m; 91 } 92 93 if (!TOO_SMALL(n)) { 94 /* 95 * If we get this far, we know that n is large and s is 96 * word-aligned. 97 */ 98 aligned_addr = (unsigned long *)s; 99 100 /* Store D into each char sized location in BUFFER so that 101 we can set large blocks quickly. */ 102 buffer = (d << 8) | d; 103 buffer |= (buffer << 16); 104 for (i = 32; i < LBLOCKSIZE * 8; i <<= 1) 105 buffer = (buffer << i) | buffer; 106 107 /* Unroll the loop. */ 108 while (n >= LBLOCKSIZE * 4) { 109 *aligned_addr++ = buffer; 110 *aligned_addr++ = buffer; 111 *aligned_addr++ = buffer; 112 *aligned_addr++ = buffer; 113 n -= 4 * LBLOCKSIZE; 114 } 115 116 while (n >= LBLOCKSIZE) { 117 *aligned_addr++ = buffer; 118 n -= LBLOCKSIZE; 119 } 120 /* Pick up the remainder with a bytewise loop. */ 121 s = (char *)aligned_addr; 122 } 123 #endif /* not PREFER_SIZE_OVER_SPEED */ 124 125 while (n--) 126 *s++ = (char)c; 127 128 return m; 129 } 130