libsyscall/wrappers/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
  33 #include "strings.h"
  34 #include <sys/types.h>
  35
  36 #define wsize   sizeof(u_int)
  37 #define wmask   (wsize - 1)
  38
  39 // n.b. this must be compiled with -fno-builtin or it might get optimized into
  40 // a recursive call to bzero.
  41 __attribute__((visibility("hidden")))
  42 void
  43 _libkernel_bzero(void *dst0, size_t length)
  44 {
  45         return (void)_libkernel_memset(dst0, 0, length);
  46 }
  47
  48 #define RETURN  return (dst0)
  49 #define VAL     c0
  50 #define WIDEVAL c
  51
  52 __attribute__((visibility("hidden")))
  53 void *
  54 _libkernel_memset(void *dst0, int c0, size_t length)
  55 {
  56         size_t t;
  57         u_int c;
  58         u_char *dst;
  59
  60         dst = dst0;
  61         /*
  62          * If not enough words, just fill bytes.  A length >= 2 words
  63          * guarantees that at least one of them is `complete' after
  64          * any necessary alignment.  For instance:
  65          *
  66          *      |-----------|-----------|-----------|
  67          *      |00|01|02|03|04|05|06|07|08|09|0A|00|
  68          *                ^---------------------^
  69          *               dst             dst+length-1
  70          *
  71          * but we use a minimum of 3 here since the overhead of the code
  72          * to do word writes is substantial.
  73          */
  74         if (length < 3 * wsize) {
  75                 while (length != 0) {
  76                         *dst++ = VAL;
  77                         --length;
  78                 }
  79                 RETURN;
  80         }
  81
  82         if ((c = (u_char)c0) != 0) {    /* Fill the word. */
  83                 c = (c << 8) | c;       /* u_int is 16 bits. */
  84 #if UINT_MAX > 0xffff
  85                 c = (c << 16) | c;      /* u_int is 32 bits. */
  86 #endif
  87 #if UINT_MAX > 0xffffffff
  88                 c = (c << 32) | c;      /* u_int is 64 bits. */
  89 #endif
  90         }
  91         /* Align destination by filling in bytes. */
  92         if ((t = (long)dst & wmask) != 0) {
  93                 t = wsize - t;
  94                 length -= t;
  95                 do {
  96                         *dst++ = VAL;
  97                 } while (--t != 0);
  98         }
  99
 100         /* Fill words.  Length was >= 2*words so we know t >= 1 here. */
 101         t = length / wsize;
 102         do {
 103                 *(u_int *)dst = WIDEVAL;
 104                 dst += wsize;
 105         } while (--t != 0);
 106
 107         /* Mop up trailing bytes, if any. */
 108         t = length & wmask;
 109         if (t != 0) {
 110                 do {
 111                         *dst++ = VAL;
 112                 } while (--t != 0);
 113         }
 114         RETURN;
 115 }