arbitrary precision integer support
[libav.git] / libavcodec / integer.c
CommitLineData
29adde83
MN
1/*
2 * arbitrary precision integers
3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 *
19 */
20
21/**
22 * @file integer.c
23 * arbitrary precision integers.
24 * @author Michael Niedermayer <michaelni@gmx.at>
25 */
26
27#include "common.h"
28#include "integer.h"
29
30AVInteger av_add_i(AVInteger a, AVInteger b){
31 int i, carry=0;
32
33 for(i=0; i<AV_INTEGER_SIZE; i++){
34 carry= (carry>>16) + a.v[i] + b.v[i];
35 a.v[i]= carry;
36 }
37 return a;
38}
39
40AVInteger av_sub_i(AVInteger a, AVInteger b){
41 int i, carry=0;
42
43 for(i=0; i<AV_INTEGER_SIZE; i++){
44 carry= (carry>>16) + a.v[i] - b.v[i];
45 a.v[i]= carry;
46 }
47 return a;
48}
49
50int av_log2_i(AVInteger a){
51 int i;
52
53 for(i=AV_INTEGER_SIZE-1; i>=0; i--){
54 if(a.v[i])
55 return av_log2_16bit(a.v[i]) + 16*i;
56 }
57 return -1;
58}
59
60AVInteger av_mul_i(AVInteger a, AVInteger b){
61 AVInteger out;
62 int i, j;
63 int na= (av_log2_i(a)+16) >> 4;
64 int nb= (av_log2_i(b)+16) >> 4;
65
66 memset(&out, 0, sizeof(out));
67
68 for(i=0; i<na; i++){
69 unsigned int carry=0;
70
71 if(a.v[i])
72 for(j=i; j<AV_INTEGER_SIZE && j-i<=nb; j++){
73 carry= (carry>>16) + out.v[j] + a.v[i]*b.v[j-i];
74 out.v[j]= carry;
75 }
76 }
77
78 return out;
79}
80
81int av_cmp_i(AVInteger a, AVInteger b){
82 int i;
83 int v= (int16_t)a.v[AV_INTEGER_SIZE-1] - (int16_t)b.v[AV_INTEGER_SIZE-1];
84 if(v) return (v>>16)|1;
85
86 for(i=AV_INTEGER_SIZE-2; i>=0; i--){
87 int v= a.v[i] - b.v[i];
88 if(v) return (v>>16)|1;
89 }
90 return 0;
91}
92
93AVInteger av_shr_i(AVInteger a, int s){
94 AVInteger out;
95 int i;
96
97 for(i=0; i<AV_INTEGER_SIZE; i++){
98 int index= i + (s>>4);
99 unsigned int v=0;
100 if(index+1<AV_INTEGER_SIZE && index+1>=0) v = a.v[index+1]<<16;
101 if(index <AV_INTEGER_SIZE && index >=0) v+= a.v[index ];
102 out.v[i]= v >> (s&15);
103 }
104 return out;
105}
106
107AVInteger av_mod_i(AVInteger *quot, AVInteger a, AVInteger b){
108 int i= av_log2_i(a) - av_log2_i(b);
109 AVInteger quot_temp;
110 if(!quot) quot = &quot_temp;
111
112 assert((int16_t)a[AV_INTEGER_SIZE-1] >= 0 && (int16_t)b[AV_INTEGER_SIZE-1] >= 0);
113 assert(av_log2(b)>=0);
114
115 if(i > 0)
116 b= av_shr_i(b, -i);
117
118 memset(quot, 0, sizeof(AVInteger));
119
120 while(i-- >= 0){
121 *quot= av_shr_i(*quot, -1);
122 if(av_cmp_i(a, b) >= 0){
123 a= av_sub_i(a, b);
124 quot->v[0] += 1;
125 }
126 b= av_shr_i(b, 1);
127 }
128 return a;
129}
130
131AVInteger av_div_i(AVInteger a, AVInteger b){
132 AVInteger quot;
133 av_mod_i(&quot, a, b);
134 return quot;
135}
136
137AVInteger av_int2i(int64_t a){
138 AVInteger out;
139 int i;
140
141 for(i=0; i<AV_INTEGER_SIZE; i++){
142 out.v[i]= a;
143 a>>=16;
144 }
145 return out;
146}
147
148int64_t av_i2int(AVInteger a){
149 int i;
150 int64_t out=(int8_t)a.v[AV_INTEGER_SIZE-1];
151
152 for(i= AV_INTEGER_SIZE-2; i>=0; i--){
153 out = (out<<16) + a.v[i];
154 }
155 return out;
156}
157
158#if 0
159#undef NDEBUG
160#include <assert.h>
161
162const uint8_t ff_log2_tab[256]={
163 0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
164 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
165 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
166 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
167 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
168 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
169 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
170 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
171};
172
173main(){
174 int64_t a,b;
175
176 for(a=7; a<256*256*256; a+=13215){
177 for(b=3; b<256*256*256; b+=27118){
178 AVInteger ai= av_int2i(a);
179 AVInteger bi= av_int2i(b);
180
181 assert(av_i2int(ai) == a);
182 assert(av_i2int(bi) == b);
183 assert(av_i2int(av_add_i(ai,bi)) == a+b);
184 assert(av_i2int(av_sub_i(ai,bi)) == a-b);
185 assert(av_i2int(av_mul_i(ai,bi)) == a*b);
186 assert(av_i2int(av_shr_i(ai, 9)) == a>>9);
187 assert(av_i2int(av_shr_i(ai,-9)) == a<<9);
188 assert(av_i2int(av_shr_i(ai, 17)) == a>>17);
189 assert(av_i2int(av_shr_i(ai,-17)) == a<<17);
190 assert(av_log2_i(ai) == av_log2(a));
191 assert(av_i2int(av_div_i(ai,bi)) == a/b);
192 }
193 }
194}
195#endif