usr/src/lib/libast/common/string/swapmem.c

   1 /***********************************************************************
   2 *                                                                      *
   3 *               This software is part of the ast package               *
   4 *          Copyright (c) 1985-2010 AT&T Intellectual Property          *
   5 *                      and is licensed under the                       *
   6 *                  Common Public License, Version 1.0                  *
   7 *                    by AT&T Intellectual Property                     *
   8 *                                                                      *
   9 *                A copy of the License is available at                 *
  10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
  11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
  12 *                                                                      *
  13 *              Information and Software Systems Research               *
  14 *                            AT&T Research                             *
  15 *                           Florham Park NJ                            *
  16 *                                                                      *
  17 *                 Glenn Fowler <gsf@research.att.com>                  *
  18 *                  David Korn <dgk@research.att.com>                   *
  19 *                   Phong Vo <kpv@research.att.com>                    *
  20 *                                                                      *
  21 ***********************************************************************/
  22 #pragma prototyped
  23 /*
  24  * Glenn Fowler
  25  * AT&T Research
  26  *
  27  * internal representation conversion support
  28  */
  29
  30 #include <ast.h>
  31 #include <swap.h>
  32
  33 /*
  34  * swap n bytes according to op
  35  * from==to is ok
  36  */
  37
  38 void*
  39 swapmem(int op, const void* from, void* to, register size_t n)
  40 {
  41         register char*  f = (char*)from;
  42         register char*  t = (char*)to;
  43         register int    c;
  44
  45         switch (op & (n - 1))
  46         {
  47         case 0:
  48                 if (t != f)
  49                         memcpy(t, f, n);
  50                 break;
  51         case 1:
  52                 for (n >>= 1; n--; f += 2, t += 2)
  53                 {
  54                         c = f[0]; t[0] = f[1]; t[1] = c;
  55                 }
  56                 break;
  57         case 2:
  58                 for (n >>= 2; n--; f += 4, t += 4)
  59                 {
  60                         c = f[0]; t[0] = f[2]; t[2] = c;
  61                         c = f[1]; t[1] = f[3]; t[3] = c;
  62                 }
  63                 break;
  64         case 3:
  65                 for (n >>= 2; n--; f += 4, t += 4)
  66                 {
  67                         c = f[0]; t[0] = f[3]; t[3] = c;
  68                         c = f[1]; t[1] = f[2]; t[2] = c;
  69                 }
  70                 break;
  71         case 4:
  72                 for (n >>= 3; n--; f += 8, t += 8)
  73                 {
  74                         c = f[0]; t[0] = f[4]; t[4] = c;
  75                         c = f[1]; t[1] = f[5]; t[5] = c;
  76                         c = f[2]; t[2] = f[6]; t[6] = c;
  77                         c = f[3]; t[3] = f[7]; t[7] = c;
  78                 }
  79                 break;
  80         case 5:
  81                 for (n >>= 3; n--; f += 8, t += 8)
  82                 {
  83                         c = f[0]; t[0] = f[5]; t[5] = c;
  84                         c = f[1]; t[1] = f[4]; t[4] = c;
  85                         c = f[2]; t[2] = f[7]; t[7] = c;
  86                         c = f[3]; t[3] = f[6]; t[6] = c;
  87                 }
  88                 break;
  89         case 6:
  90                 for (n >>= 3; n--; f += 8, t += 8)
  91                 {
  92                         c = f[0]; t[0] = f[6]; t[6] = c;
  93                         c = f[1]; t[1] = f[7]; t[7] = c;
  94                         c = f[2]; t[2] = f[4]; t[4] = c;
  95                         c = f[3]; t[3] = f[5]; t[5] = c;
  96                 }
  97                 break;
  98         case 7:
  99                 for (n >>= 3; n--; f += 8, t += 8)
 100                 {
 101                         c = f[0]; t[0] = f[7]; t[7] = c;
 102                         c = f[1]; t[1] = f[6]; t[6] = c;
 103                         c = f[2]; t[2] = f[5]; t[5] = c;
 104                         c = f[3]; t[3] = f[4]; t[4] = c;
 105                 }
 106                 break;
 107         }
 108         return to;
 109 }