1/*
2 * Fixed point type.
3 * Based on Allegro library by Shawn Hargreaves.
4 */
5
6#ifndef FIXMATH_FIXMATH_H
7#define FIXMATH_FIXMATH_H
8
9#include "base/ints.h"
10#include <cerrno>
11
12namespace fixmath {
13
14 typedef int32_t fixed;
15
16 extern const fixed fixtorad_r;
17 extern const fixed radtofix_r;
18
19 extern fixed _cos_tbl[];
20 extern fixed _tan_tbl[];
21 extern fixed _acos_tbl[];
22
23 fixed fixsqrt(fixed x);
24 fixed fixhypot(fixed x, fixed y);
25 fixed fixatan(fixed x);
26 fixed fixatan2(fixed y, fixed x);
27
28 // ftofix and fixtof are used in generic C versions of fixmul and fixdiv
29 inline fixed ftofix(double x) {
30 if (x > 32767.0) {
31 errno = ERANGE;
32 return 0x7FFFFFFF;
33 }
34
35 if (x < -32767.0) {
36 errno = ERANGE;
37 return -0x7FFFFFFF;
38 }
39
40 return (fixed)(x * 65536.0 + (x < 0 ? -0.5 : 0.5));
41 }
42
43 inline double fixtof(fixed x) {
44 return (double)x / 65536.0;
45 };
46
47 inline fixed fixadd(fixed x, fixed y) {
48 fixed result = x + y;
49
50 if (result >= 0) {
51 if ((x < 0) && (y < 0)) {
52 errno = ERANGE;
53 return -0x7FFFFFFF;
54 }
55 else
56 return result;
57 }
58 else {
59 if ((x > 0) && (y > 0)) {
60 errno = ERANGE;
61 return 0x7FFFFFFF;
62 }
63 else
64 return result;
65 }
66 }
67
68 inline fixed fixsub(fixed x, fixed y) {
69 fixed result = x - y;
70
71 if (result >= 0) {
72 if ((x < 0) && (y > 0)) {
73 errno = ERANGE;
74 return -0x7FFFFFFF;
75 }
76 else
77 return result;
78 }
79 else {
80 if ((x > 0) && (y < 0)) {
81 errno = ERANGE;
82 return 0x7FFFFFFF;
83 }
84 else
85 return result;
86 }
87 }
88
89 inline fixed fixmul(fixed x, fixed y) {
90 return ftofix(fixtof(x) * fixtof(y));
91 }
92
93 inline fixed fixdiv(fixed x, fixed y) {
94 if (y == 0) {
95 errno = ERANGE;
96 return (x < 0) ? -0x7FFFFFFF : 0x7FFFFFFF;
97 }
98 else
99 return ftofix(fixtof(x) / fixtof(y));
100 }
101
102 inline int fixfloor(fixed x) {
103 /* (x >> 16) is not portable */
104 if (x >= 0)
105 return (x >> 16);
106 else
107 return ~((~x) >> 16);
108 }
109
110 inline int fixceil(fixed x) {
111 if (x > 0x7FFF0000) {
112 errno = ERANGE;
113 return 0x7FFF;
114 }
115
116 return fixfloor(x + 0xFFFF);
117 }
118
119 inline fixed itofix(int x) {
120 return x << 16;
121 }
122
123 inline int fixtoi(fixed x) {
124 return fixfloor(x) + ((x & 0x8000) >> 15);
125 }
126
127 inline fixed fixcos(fixed x) {
128 return _cos_tbl[((x + 0x4000) >> 15) & 0x1FF];
129 }
130
131 inline fixed fixsin(fixed x) {
132 return _cos_tbl[((x - 0x400000 + 0x4000) >> 15) & 0x1FF];
133 }
134
135 inline fixed fixtan(fixed x) {
136 return _tan_tbl[((x + 0x4000) >> 15) & 0xFF];
137 }
138
139 inline fixed fixacos(fixed x) {
140 if ((x < -65536) || (x > 65536)) {
141 errno = EDOM;
142 return 0;
143 }
144
145 return _acos_tbl[(x+65536+127)>>8];
146 }
147
148 inline fixed fixasin(fixed x) {
149 if ((x < -65536) || (x > 65536)) {
150 errno = EDOM;
151 return 0;
152 }
153
154 return 0x00400000 - _acos_tbl[(x+65536+127)>>8];
155 }
156
157} // namespace fixmath
158
159#endif
160