angel_bytesex.c revision 1.3 
1/*
2 * Copyright (C) 1995 Advanced RISC Machines Limited. All rights reserved.
3 *
4 * This software may be freely used, copied, modified, and distributed
5 * provided that the above copyright notice is preserved in all copies of the
6 * software.
7 */
8
9/*
10 * angel_bytesex.c - Code to support byte-sex independence
11 * Copyright: (C) 1991, Advanced RISC Machines Ltd., Cambridge, England.
12 */
13
14/*
15 * RCS $Revision: 1.3 $
16 * Checkin $Date: 2004/12/27 14:00:53 $
17 */
18
19#include "angel_bytesex.h"
20
21static int reversing_bytes = 0;
22
23void bytesex_reverse(yes_or_no)
24int yes_or_no;
25{ reversing_bytes = yes_or_no;
26}
27
28int bytesex_reversing()
29{
30  return reversing_bytes;
31}
32
33int32 bytesex_hostval(v)
34int32 v;
35{ /* Return v with the same endian-ness as the host */
36  /* This mess generates better ARM code than the more obvious mess */
37  /* and may eventually peephole to optimal code...                 */
38  if (reversing_bytes)
39  { unsigned32 t;
40    /* t = v ^ (v ror 16) */
41    t = v ^ ((v << 16) | (((unsigned32)v) >> 16));
42    t &= ~0xff0000;
43    /* v = v ror 8 */
44    v = (v << 24) | (((unsigned32)v) >> 8);
45    v = v ^ (t >> 8);
46  }
47  return v;
48}
49
50int32 bytesex_hostval_16(v)
51int32 v;
52{
53  if (reversing_bytes) {
54    v = ((v >> 8) & 0xff) | ((v << 8) & 0xff00);
55  }
56  return v;
57}
58