lib/libc/string/memset.c

   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  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * 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 REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)memset.c 8.1 (Berkeley) 6/4/93
  33  * $FreeBSD: src/lib/libc/string/memset.c,v 1.9 2007/01/09 00:28:12 imp Exp $
  34  * $DragonFly: src/lib/libc/string/memset.c,v 1.4 2005/09/18 16:32:34 asmodai Exp $
  35  */
  36
  37 #include <sys/types.h>
  38
  39 #include <limits.h>
  40
  41 #define wsize   sizeof(u_int)
  42 #define wmask   (wsize - 1)
  43
  44 #ifdef BZERO
  45 #include <strings.h>
  46
  47 #define RETURN  return
  48 #define VAL     0
  49 #define WIDEVAL 0
  50
  51 void
  52 bzero(void *dst0, size_t length)
  53 #else
  54 #include <string.h>
  55
  56 #define RETURN  return (dst0)
  57 #define VAL     c0
  58 #define WIDEVAL c
  59
  60 void *
  61 memset(void *dst0, int c0, size_t length)
  62 #endif
  63 {
  64         size_t t;
  65 #ifndef BZERO
  66         u_int c;
  67 #endif
  68         u_char *dst;
  69
  70         dst = dst0;
  71         /*
  72          * If not enough words, just fill bytes.  A length >= 2 words
  73          * guarantees that at least one of them is `complete' after
  74          * any necessary alignment.  For instance:
  75          *
  76          *      |-----------|-----------|-----------|
  77          *      |00|01|02|03|04|05|06|07|08|09|0A|00|
  78          *                ^---------------------^
  79          *               dst             dst+length-1
  80          *
  81          * but we use a minimum of 3 here since the overhead of the code
  82          * to do word writes is substantial.
  83          */
  84         if (length < 3 * wsize) {
  85                 while (length != 0) {
  86                         *dst++ = VAL;
  87                         --length;
  88                 }
  89                 RETURN;
  90         }
  91
  92 #ifndef BZERO
  93         if ((c = (u_char)c0) != 0) {    /* Fill the word. */
  94                 c = (c << 8) | c;       /* u_int is 16 bits. */
  95 #if UINT_MAX > 0xffff
  96                 c = (c << 16) | c;      /* u_int is 32 bits. */
  97 #endif
  98 #if UINT_MAX > 0xffffffff
  99                 c = (c << 32) | c;      /* u_int is 64 bits. */
 100 #endif
 101         }
 102 #endif
 103         /* Align destination by filling in bytes. */
 104         if ((t = (long)dst & wmask) != 0) {
 105                 t = wsize - t;
 106                 length -= t;
 107                 do {
 108                         *dst++ = VAL;
 109                 } while (--t != 0);
 110         }
 111
 112         /* Fill words.  Length was >= 2*words so we know t >= 1 here. */
 113         t = length / wsize;
 114         do {
 115                 *(u_int *)dst = WIDEVAL;
 116                 dst += wsize;
 117         } while (--t != 0);
 118
 119         /* Mop up trailing bytes, if any. */
 120         t = length & wmask;
 121         if (t != 0)
 122                 do {
 123                         *dst++ = VAL;
 124                 } while (--t != 0);
 125         RETURN;
 126 }