Code clean-up for crc.c, lfg.c, log.c, random_see.d, rational.c and tree.c.
[libav.git] / libavutil / rational.c
1 /*
2 * rational numbers
3 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of Libav.
6 *
7 * Libav is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * Libav is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file
24 * rational numbers
25 * @author Michael Niedermayer <michaelni@gmx.at>
26 */
27
28 #include "avassert.h"
29 //#include <math.h>
30 #include <limits.h>
31
32 #include "common.h"
33 #include "mathematics.h"
34 #include "rational.h"
35
36 int av_reduce(int *dst_num, int *dst_den,
37 int64_t num, int64_t den, int64_t max)
38 {
39 AVRational a0 = { 0, 1 }, a1 = { 1, 0 };
40 int sign = (num < 0) ^ (den < 0);
41 int64_t gcd = av_gcd(FFABS(num), FFABS(den));
42
43 if (gcd) {
44 num = FFABS(num) / gcd;
45 den = FFABS(den) / gcd;
46 }
47 if (num <= max && den <= max) {
48 a1 = (AVRational) { num, den };
49 den = 0;
50 }
51
52 while (den) {
53 uint64_t x = num / den;
54 int64_t next_den = num - den * x;
55 int64_t a2n = x * a1.num + a0.num;
56 int64_t a2d = x * a1.den + a0.den;
57
58 if (a2n > max || a2d > max) {
59 if (a1.num) x = (max - a0.num) / a1.num;
60 if (a1.den) x = FFMIN(x, (max - a0.den) / a1.den);
61
62 if (den * (2 * x * a1.den + a0.den) > num * a1.den)
63 a1 = (AVRational) { x * a1.num + a0.num, x * a1.den + a0.den };
64 break;
65 }
66
67 a0 = a1;
68 a1 = (AVRational) { a2n, a2d };
69 num = den;
70 den = next_den;
71 }
72 av_assert2(av_gcd(a1.num, a1.den) <= 1U);
73
74 *dst_num = sign ? -a1.num : a1.num;
75 *dst_den = a1.den;
76
77 return den == 0;
78 }
79
80 AVRational av_mul_q(AVRational b, AVRational c)
81 {
82 av_reduce(&b.num, &b.den,
83 b.num * (int64_t) c.num,
84 b.den * (int64_t) c.den, INT_MAX);
85 return b;
86 }
87
88 AVRational av_div_q(AVRational b, AVRational c)
89 {
90 return av_mul_q(b, (AVRational) { c.den, c.num });
91 }
92
93 AVRational av_add_q(AVRational b, AVRational c) {
94 av_reduce(&b.num, &b.den,
95 b.num * (int64_t) c.den +
96 c.num * (int64_t) b.den,
97 b.den * (int64_t) c.den, INT_MAX);
98 return b;
99 }
100
101 AVRational av_sub_q(AVRational b, AVRational c)
102 {
103 return av_add_q(b, (AVRational) { -c.num, c.den });
104 }
105
106 AVRational av_d2q(double d, int max)
107 {
108 AVRational a;
109 #define LOG2 0.69314718055994530941723212145817656807550013436025
110 int exponent;
111 int64_t den;
112 if (isnan(d))
113 return (AVRational) { 0,0 };
114 if (isinf(d))
115 return (AVRational) { d < 0 ? -1 : 1, 0 };
116 exponent = FFMAX( (int)(log(fabs(d) + 1e-20)/LOG2), 0);
117 den = 1LL << (61 - exponent);
118 av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max);
119
120 return a;
121 }
122
123 int av_nearer_q(AVRational q, AVRational q1, AVRational q2)
124 {
125 /* n/d is q, a/b is the median between q1 and q2 */
126 int64_t a = q1.num * (int64_t)q2.den + q2.num * (int64_t)q1.den;
127 int64_t b = 2 * (int64_t)q1.den * q2.den;
128
129 /* rnd_up(a*d/b) > n => a*d/b > n */
130 int64_t x_up = av_rescale_rnd(a, q.den, b, AV_ROUND_UP);
131
132 /* rnd_down(a*d/b) < n => a*d/b < n */
133 int64_t x_down = av_rescale_rnd(a, q.den, b, AV_ROUND_DOWN);
134
135 return ((x_up > q.num) - (x_down < q.num)) * av_cmp_q(q2, q1);
136 }
137
138 int av_find_nearest_q_idx(AVRational q, const AVRational* q_list)
139 {
140 int i, nearest_q_idx = 0;
141 for (i = 0; q_list[i].den; i++)
142 if (av_nearer_q(q, q_list[i], q_list[nearest_q_idx]) > 0)
143 nearest_q_idx = i;
144
145 return nearest_q_idx;
146 }
147
148 #ifdef TEST
149 int main(void)
150 {
151 AVRational a,b;
152 for (a.num = -2; a.num <= 2; a.num++) {
153 for (a.den = -2; a.den <= 2; a.den++) {
154 for (b.num = -2; b.num <= 2; b.num++) {
155 for (b.den = -2; b.den <= 2; b.den++) {
156 int c = av_cmp_q(a,b);
157 double d = av_q2d(a) == av_q2d(b) ?
158 0 : (av_q2d(a) - av_q2d(b));
159 if (d > 0) d = 1;
160 else if (d < 0) d = -1;
161 else if (d != d) d = INT_MIN;
162 if (c != d)
163 av_log(0, AV_LOG_ERROR, "%d/%d %d/%d, %d %f\n", a.num,
164 a.den, b.num, b.den, c,d);
165 }
166 }
167 }
168 }
169 return 0;
170 }
171 #endif