clib/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  * 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 #include "config.h"
  38
  39 #if defined(LIBC_SCCS) && !defined(lint)
  40 static const char sccsid[] = "@(#)memset.c      8.1 (Berkeley) 6/4/93";
  41 #endif /* LIBC_SCCS and not lint */
  42
  43 #include <sys/types.h>
  44
  45 #include <limits.h>
  46 #include <string.h>
  47
  48 /*
  49  * PUBLIC: #ifndef HAVE_MEMSET
  50  * PUBLIC: void *memset __P((void *, int, size_t));
  51  * PUBLIC: #endif
  52  */
  53 #define wsize   sizeof(u_int)
  54 #define wmask   (wsize - 1)
  55
  56 #ifdef BZERO
  57 #define RETURN  return
  58 #define VAL     0
  59 #define WIDEVAL 0
  60
  61 void
  62 bzero(dst0, length)
  63         void *dst0;
  64         register size_t length;
  65 #else
  66 #define RETURN  return (dst0)
  67 #define VAL     c0
  68 #define WIDEVAL c
  69
  70 void *
  71 memset(void *dst0, register int c0, register size_t length)
  72
  73
  74
  75 #endif
  76 {
  77         register size_t t;
  78         register u_int c;
  79         register u_char *dst;
  80
  81         dst = dst0;
  82         /*
  83          * If not enough words, just fill bytes.  A length >= 2 words
  84          * guarantees that at least one of them is `complete' after
  85          * any necessary alignment.  For instance:
  86          *
  87          *      |-----------|-----------|-----------|
  88          *      |00|01|02|03|04|05|06|07|08|09|0A|00|
  89          *                ^---------------------^
  90          *               dst             dst+length-1
  91          *
  92          * but we use a minimum of 3 here since the overhead of the code
  93          * to do word writes is substantial.
  94          */
  95         if (length < 3 * wsize) {
  96                 while (length != 0) {
  97                         *dst++ = VAL;
  98                         --length;
  99                 }
 100                 RETURN;
 101         }
 102
 103 #ifndef BZERO
 104         if ((c = (u_char)c0) != 0) {    /* Fill the word. */
 105                 c = (c << 8) | c;       /* u_int is 16 bits. */
 106 #if UINT_MAX > 0xffff
 107                 c = (c << 16) | c;      /* u_int is 32 bits. */
 108 #endif
 109 #if UINT_MAX > 0xffffffff
 110                 c = (c << 32) | c;      /* u_int is 64 bits. */
 111 #endif
 112         }
 113 #endif
 114         /* Align destination by filling in bytes. */
 115         if ((t = (int)dst & wmask) != 0) {
 116                 t = wsize - t;
 117                 length -= t;
 118                 do {
 119                         *dst++ = VAL;
 120                 } while (--t != 0);
 121         }
 122
 123         /* Fill words.  Length was >= 2*words so we know t >= 1 here. */
 124         t = length / wsize;
 125         do {
 126                 *(u_int *)dst = WIDEVAL;
 127                 dst += wsize;
 128         } while (--t != 0);
 129
 130         /* Mop up trailing bytes, if any. */
 131         t = length & wmask;
 132         if (t != 0)
 133                 do {
 134                         *dst++ = VAL;
 135                 } while (--t != 0);
 136         RETURN;
 137 }