1/***********************************************************************
2*                                                                      *
3*               This software is part of the ast package               *
4*          Copyright (c) 1985-2011 AT&T Intellectual Property          *
5*                      and is licensed under the                       *
6*                 Eclipse Public License, Version 1.0                  *
7*                    by AT&T Intellectual Property                     *
8*                                                                      *
9*                A copy of the License is available at                 *
10*          http://www.eclipse.org/org/documents/epl-v10.html           *
11*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *
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
38void*
39swapmem(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}
110