reactos/sdk/tools/mkisofs/schilytools/libschily/zerobytes.c

   1 /* @(#)zerobytes.c      1.2 11/07/30 Copyright Copyright 1987, 1995-2011 J. Schilling */
   2 /*
   3  *      fill memory with null bytes
   4  *
   5  *      Copyright (c) 1987, 1995-2011 J. Schilling
   6  */
   7 /*
   8  * The contents of this file are subject to the terms of the
   9  * Common Development and Distribution License, Version 1.0 only
  10  * (the "License").  You may not use this file except in compliance
  11  * with the License.
  12  *
  13  * See the file CDDL.Schily.txt in this distribution for details.
  14  *
  15  * When distributing Covered Code, include this CDDL HEADER in each
  16  * file and include the License file CDDL.Schily.txt from this distribution.
  17  */
  18
  19 #include <schily/standard.h>
  20 #include <schily/align.h>
  21 #include <schily/types.h>
  22 #include <schily/schily.h>
  23
  24 #define DO8(a)  a; a; a; a; a; a; a; a;
  25
  26 /*
  27  * zero(to, cnt)
  28  */
  29 EXPORT char *
  30 zerobytes(tov, cnt)
  31         void    *tov;
  32         ssize_t cnt;
  33 {
  34         register char   *to = (char *)tov;
  35         register ssize_t n;
  36         register long   lval = 0L;
  37
  38         /*
  39          * If we change cnt to be unsigned, check for == instead of <=
  40          */
  41         if ((n = cnt) <= 0)
  42                 return (to);
  43
  44         if (n < 8 * sizeof (long)) {    /* Simple may be faster... */
  45                 do {                    /* n is always > 0 */
  46                         *to++ = '\0';
  47                 } while (--n > 0);
  48                 return (to);
  49         }
  50
  51         /*
  52          * Assign byte-wise until properly aligned for a long pointer.
  53          */
  54         while (--n >= 0 && !laligned(to)) {
  55                 *to++ = '\0';
  56         }
  57         n++;
  58
  59         if (n >= (ssize_t)(8 * sizeof (long))) {
  60                 register ssize_t rem = n % (8 * sizeof (long));
  61
  62                 n /= (8 * sizeof (long));
  63                 {
  64                         register long *tol = (long *)to;
  65
  66                         do {
  67                                 DO8 (*tol++ = lval);
  68                         } while (--n > 0);
  69
  70                         to = (char *)tol;
  71                 }
  72                 n = rem;
  73
  74                 if (n >= 8) {
  75                         n -= 8;
  76                         do {
  77                                 DO8 (*to++ = '\0');
  78                         } while ((n -= 8) >= 0);
  79                         n += 8;
  80                 }
  81                 if (n > 0) do {
  82                         *to++ = '\0';
  83                 } while (--n > 0);
  84                 return (to);
  85         }
  86         if (n > 0) do {
  87                 *to++ = '\0';
  88         } while (--n > 0);
  89         return (to);
  90 }