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