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Linux kernel mirror (for testing)
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1#ifndef _FIXP_ARITH_H
2#define _FIXP_ARITH_H
3
4/*
5 * $$
6 *
7 * Simplistic fixed-point arithmetics.
8 * Hmm, I'm probably duplicating some code :(
9 *
10 * Copyright (c) 2002 Johann Deneux
11 */
12
13/*
14 * This program is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License as published by
16 * the Free Software Foundation; either version 2 of the License, or
17 * (at your option) any later version.
18 *
19 * This program is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU General Public License for more details.
23 *
24 * You should have received a copy of the GNU General Public License
25 * along with this program; if not, write to the Free Software
26 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
27 *
28 * Should you need to contact me, the author, you can do so by
29 * e-mail - mail your message to <deneux@ifrance.com>
30 */
31
32#include <linux/types.h>
33
34// The type representing fixed-point values
35typedef s16 fixp_t;
36
37#define FRAC_N 8
38#define FRAC_MASK ((1<<FRAC_N)-1)
39
40// Not to be used directly. Use fixp_{cos,sin}
41static const fixp_t cos_table[45] = {
42 0x0100, 0x00FF, 0x00FF, 0x00FE, 0x00FD, 0x00FC, 0x00FA, 0x00F8,
43 0x00F6, 0x00F3, 0x00F0, 0x00ED, 0x00E9, 0x00E6, 0x00E2, 0x00DD,
44 0x00D9, 0x00D4, 0x00CF, 0x00C9, 0x00C4, 0x00BE, 0x00B8, 0x00B1,
45 0x00AB, 0x00A4, 0x009D, 0x0096, 0x008F, 0x0087, 0x0080, 0x0078,
46 0x0070, 0x0068, 0x005F, 0x0057, 0x004F, 0x0046, 0x003D, 0x0035,
47 0x002C, 0x0023, 0x001A, 0x0011, 0x0008
48};
49
50
51/* a: 123 -> 123.0 */
52static inline fixp_t fixp_new(s16 a)
53{
54 return a<<FRAC_N;
55}
56
57/* a: 0xFFFF -> -1.0
58 0x8000 -> 1.0
59 0x0000 -> 0.0
60*/
61static inline fixp_t fixp_new16(s16 a)
62{
63 return ((s32)a)>>(16-FRAC_N);
64}
65
66static inline fixp_t fixp_cos(unsigned int degrees)
67{
68 int quadrant = (degrees / 90) & 3;
69 unsigned int i = degrees % 90;
70
71 if (quadrant == 1 || quadrant == 3) {
72 i = 89 - i;
73 }
74
75 i >>= 1;
76
77 return (quadrant == 1 || quadrant == 2)? -cos_table[i] : cos_table[i];
78}
79
80static inline fixp_t fixp_sin(unsigned int degrees)
81{
82 return -fixp_cos(degrees + 90);
83}
84
85static inline fixp_t fixp_mult(fixp_t a, fixp_t b)
86{
87 return ((s32)(a*b))>>FRAC_N;
88}
89
90#endif