lib/libc/pc532/string/bzero.c

   1 /*
   2  * Mach Operating System
   3  * Copyright (c) 1991,1990,1989 Carnegie Mellon University
   4  * All Rights Reserved.
   5  *
   6  * Permission to use, copy, modify and distribute this software and its
   7  * documentation is hereby granted, provided that both the copyright
   8  * notice and this permission notice appear in all copies of the
   9  * software, derivative works or modified versions, and any portions
  10  * thereof, and that both notices appear in supporting documentation.
  11  *
  12  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  13  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  14  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  15  *
  16  * Carnegie Mellon requests users of this software to return to
  17  *
  18  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  19  *  School of Computer Science
  20  *  Carnegie Mellon University
  21  *  Pittsburgh PA 15213-3890
  22  *
  23  * any improvements or extensions that they make and grant Carnegie Mellon
  24  * the rights to redistribute these changes.
  25  */
  26 /*
  27  *      $Id: bzero.c,v 1.1 1993/09/17 18:43:47 phil Exp $
  28  */
  29 /*
  30  *      Object:
  31  *              bzero                           EXPORTED function
  32  *
  33  *              Clear memory locations
  34  *
  35  *      Optimize for aligned memory ops, if possible and simple.
  36  *      Might need later recoding in assembly for better efficiency.
  37  */
  38 void
  39 bzero(addr, bcount)
  40         register unsigned addr;
  41         register unsigned bcount;
  42 {
  43         register int    i;
  44
  45         if (bcount == 0)        /* sanity */
  46                 return;
  47         switch (addr & 3) {
  48             case 1:
  49                 *((char *) addr++) = 0;
  50                 if (--bcount == 0)
  51                         return;
  52             case 2:
  53                 *((char *) addr++) = 0;
  54                 if (--bcount == 0)
  55                         return;
  56             case 3:
  57                 *((char *) addr++) = 0;
  58                 if (--bcount == 0)
  59                         return;
  60             default:
  61                 break;
  62         }
  63
  64         for (i = bcount >> 2; i; i--, addr += 4)
  65                 *((int *) addr) = 0;
  66
  67         switch (bcount & 3) {
  68             case 3: *((char*)addr++) = 0;
  69             case 2: *((char*)addr++) = 0;
  70             case 1: *((char*)addr++) = 0;
  71             default:break;
  72         }
  73 }