string/FreeBSD/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 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)memset.c    8.1 (Berkeley) 6/4/93";
  39 #endif /* LIBC_SCCS and not lint */
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: src/lib/libc/string/memset.c,v 1.8 2002/09/01 21:53:46 robert Exp $");
  42
  43 #include <sys/types.h>
  44
  45 #include <limits.h>
  46
  47 #define wsize   sizeof(u_int)
  48 #define wmask   (wsize - 1)
  49
  50 #ifdef BZERO
  51 #include <strings.h>
  52
  53 #define RETURN  return
  54 #define VAL     0
  55 #define WIDEVAL 0
  56
  57 void
  58 bzero(void *dst0, size_t length)
  59 #else
  60 #include <string.h>
  61
  62 #define RETURN  return (dst0)
  63 #define VAL     c0
  64 #define WIDEVAL c
  65
  66 void *
  67 memset(void *dst0, int c0, size_t length)
  68 #endif
  69 {
  70         size_t t;
  71 #ifndef BZERO
  72         u_int c;
  73 #endif
  74         u_char *dst;
  75
  76         dst = dst0;
  77         /*
  78          * If not enough words, just fill bytes.  A length >= 2 words
  79          * guarantees that at least one of them is `complete' after
  80          * any necessary alignment.  For instance:
  81          *
  82          *      |-----------|-----------|-----------|
  83          *      |00|01|02|03|04|05|06|07|08|09|0A|00|
  84          *                ^---------------------^
  85          *               dst             dst+length-1
  86          *
  87          * but we use a minimum of 3 here since the overhead of the code
  88          * to do word writes is substantial.
  89          */
  90         if (length < 3 * wsize) {
  91                 while (length != 0) {
  92                         *dst++ = VAL;
  93                         --length;
  94                 }
  95                 RETURN;
  96         }
  97
  98 #ifndef BZERO
  99         if ((c = (u_char)c0) != 0) {    /* Fill the word. */
 100                 c = (c << 8) | c;       /* u_int is 16 bits. */
 101 #if UINT_MAX > 0xffff
 102                 c = (c << 16) | c;      /* u_int is 32 bits. */
 103 #endif
 104 #if UINT_MAX > 0xffffffff
 105                 c = (c << 32) | c;      /* u_int is 64 bits. */
 106 #endif
 107         }
 108 #endif
 109         /* Align destination by filling in bytes. */
 110         if ((t = (long)dst & wmask) != 0) {
 111                 t = wsize - t;
 112                 length -= t;
 113                 do {
 114                         *dst++ = VAL;
 115                 } while (--t != 0);
 116         }
 117
 118         /* Fill words.  Length was >= 2*words so we know t >= 1 here. */
 119         t = length / wsize;
 120         do {
 121                 *(u_int *)dst = WIDEVAL;
 122                 dst += wsize;
 123         } while (--t != 0);
 124
 125         /* Mop up trailing bytes, if any. */
 126         t = length & wmask;
 127         if (t != 0)
 128                 do {
 129                         *dst++ = VAL;
 130                 } while (--t != 0);
 131         RETURN;
 132 }