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 <johann.deneux@gmail.com>
28 */
29
30 #include <linux/types.h>
31
32 /* The type representing fixed-point values */
33 typedef 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} */
39 static 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 */
fixp_new(s16 a)50 static 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 */
fixp_new16(s16 a)59 static inline fixp_t fixp_new16(s16 a)
60 {
61 return ((s32)a)>>(16-FRAC_N);
62 }
63
fixp_cos(unsigned int degrees)64 static 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
fixp_sin(unsigned int degrees)77 static inline fixp_t fixp_sin(unsigned int degrees)
78 {
79 return -fixp_cos(degrees + 90);
80 }
81
fixp_mult(fixp_t a,fixp_t b)82 static inline fixp_t fixp_mult(fixp_t a, fixp_t b)
83 {
84 return ((s32)(a*b))>>FRAC_N;
85 }
86
87 #endif
88