workbench/devs/diskimage/support/swab2.c

   1 /* Copyright 2007-2012 Fredrik Wikstrom. All rights reserved.
   2 **
   3 ** Redistribution and use in source and binary forms, with or without
   4 ** modification, are permitted provided that the following conditions
   5 ** are met:
   6 **
   7 ** 1. Redistributions of source code must retain the above copyright
   8 **    notice, this list of conditions and the following disclaimer.
   9 **
  10 ** 2. Redistributions in binary form must reproduce the above copyright
  11 **    notice, this list of conditions and the following disclaimer in the
  12 **    documentation and/or other materials provided with the distribution.
  13 **
  14 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS `AS IS'
  15 ** AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16 ** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17 ** ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  18 ** LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  19 ** CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  20 ** SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  21 ** INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  22 ** CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  23 ** ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  24 ** POSSIBILITY OF SUCH DAMAGE.
  25 */
  26
  27 #include "support.h"
  28 #include "endian.h"
  29
  30 void swab2 (CONST_APTR source, APTR dest, ULONG bytes) {
  31         ULONG longs = (bytes >> 1) >> 2;
  32         ULONG words = (bytes >> 1) & 3;
  33         const ULONG *l_src;
  34         ULONG *l_dst;
  35         const UWORD *w_src;
  36         UWORD *w_dst;
  37         const ULONG m1 = 0xff00ff00;
  38         const ULONG m2 = 0x00ff00ff;
  39         l_src = (const ULONG *)source;
  40         l_dst = (ULONG *)dest;
  41         while (longs) {
  42                 *l_dst++ = ((*l_src << 8) & m1)|((*l_src >> 8) & m2);
  43                 l_src++;
  44                 *l_dst++ = ((*l_src << 8) & m1)|((*l_src >> 8) & m2);
  45                 l_src++;
  46                 longs--;
  47         }
  48         w_src = (const UWORD *)l_src;
  49         w_dst = (UWORD *)l_dst;
  50         switch (words) {
  51                 case 3:
  52                         wswap16(w_dst++, *w_src); w_src++;
  53                 case 2:
  54                         wswap16(w_dst++, *w_src); w_src++;
  55                 case 1:
  56                         wswap16(w_dst++, *w_src); w_src++;
  57                 default:
  58                         break;
  59         }
  60 }