1 /*
2 * arbitrary precision integers
3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg 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 * FFmpeg 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 FFmpeg; 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 * arbitrary precision integers
25 * @author Michael Niedermayer <michaelni@gmx.at>
26 */
27
28 #include <string.h>
29
30 #include "integer.h"
31 #include "avassert.h"
32 #include "intmath.h"
33
34 static const AVInteger zero_i;
35
av_add_i(AVInteger a,AVInteger b)36 AVInteger av_add_i(AVInteger a, AVInteger b){
37 int i, carry=0;
38
39 for(i=0; i<AV_INTEGER_SIZE; i++){
40 carry= (carry>>16) + a.v[i] + b.v[i];
41 a.v[i]= carry;
42 }
43 return a;
44 }
45
av_sub_i(AVInteger a,AVInteger b)46 AVInteger av_sub_i(AVInteger a, AVInteger b){
47 int i, carry=0;
48
49 for(i=0; i<AV_INTEGER_SIZE; i++){
50 carry= (carry>>16) + a.v[i] - b.v[i];
51 a.v[i]= carry;
52 }
53 return a;
54 }
55
av_log2_i(AVInteger a)56 int av_log2_i(AVInteger a){
57 int i;
58
59 for(i=AV_INTEGER_SIZE-1; i>=0; i--){
60 if(a.v[i])
61 return av_log2_16bit(a.v[i]) + 16*i;
62 }
63 return -1;
64 }
65
av_mul_i(AVInteger a,AVInteger b)66 AVInteger av_mul_i(AVInteger a, AVInteger b){
67 AVInteger out;
68 int i, j;
69 int na= (av_log2_i(a)+16) >> 4;
70 int nb= (av_log2_i(b)+16) >> 4;
71
72 memset(&out, 0, sizeof(out));
73
74 for(i=0; i<na; i++){
75 unsigned int carry=0;
76
77 if(a.v[i])
78 for(j=i; j<AV_INTEGER_SIZE && j-i<=nb; j++){
79 carry= (carry>>16) + out.v[j] + a.v[i]*(unsigned)b.v[j-i];
80 out.v[j]= carry;
81 }
82 }
83
84 return out;
85 }
86
av_cmp_i(AVInteger a,AVInteger b)87 int av_cmp_i(AVInteger a, AVInteger b){
88 int i;
89 int v= (int16_t)a.v[AV_INTEGER_SIZE-1] - (int16_t)b.v[AV_INTEGER_SIZE-1];
90 if(v) return (v>>16)|1;
91
92 for(i=AV_INTEGER_SIZE-2; i>=0; i--){
93 int v= a.v[i] - b.v[i];
94 if(v) return (v>>16)|1;
95 }
96 return 0;
97 }
98
av_shr_i(AVInteger a,int s)99 AVInteger av_shr_i(AVInteger a, int s){
100 AVInteger out;
101 int i;
102
103 for(i=0; i<AV_INTEGER_SIZE; i++){
104 unsigned int index= i + (s>>4);
105 unsigned int v=0;
106 if(index+1<AV_INTEGER_SIZE) v = a.v[index+1]<<16;
107 if(index <AV_INTEGER_SIZE) v+= a.v[index ];
108 out.v[i]= v >> (s&15);
109 }
110 return out;
111 }
112
av_mod_i(AVInteger * quot,AVInteger a,AVInteger b)113 AVInteger av_mod_i(AVInteger *quot, AVInteger a, AVInteger b){
114 int i= av_log2_i(a) - av_log2_i(b);
115 AVInteger quot_temp;
116 if(!quot) quot = "_temp;
117
118 if ((int16_t)a.v[AV_INTEGER_SIZE-1] < 0) {
119 a = av_mod_i(quot, av_sub_i(zero_i, a), b);
120 *quot = av_sub_i(zero_i, *quot);
121 return av_sub_i(zero_i, a);
122 }
123
124 av_assert2((int16_t)a.v[AV_INTEGER_SIZE-1] >= 0 && (int16_t)b.v[AV_INTEGER_SIZE-1] >= 0);
125 av_assert2(av_log2_i(b)>=0);
126
127 if(i > 0)
128 b= av_shr_i(b, -i);
129
130 memset(quot, 0, sizeof(AVInteger));
131
132 while(i-- >= 0){
133 *quot= av_shr_i(*quot, -1);
134 if(av_cmp_i(a, b) >= 0){
135 a= av_sub_i(a, b);
136 quot->v[0] += 1;
137 }
138 b= av_shr_i(b, 1);
139 }
140 return a;
141 }
142
av_div_i(AVInteger a,AVInteger b)143 AVInteger av_div_i(AVInteger a, AVInteger b){
144 AVInteger quot;
145 av_mod_i(", a, b);
146 return quot;
147 }
148
av_int2i(int64_t a)149 AVInteger av_int2i(int64_t a){
150 AVInteger out;
151 int i;
152
153 for(i=0; i<AV_INTEGER_SIZE; i++){
154 out.v[i]= a;
155 a>>=16;
156 }
157 return out;
158 }
159
av_i2int(AVInteger a)160 int64_t av_i2int(AVInteger a){
161 int i;
162 int64_t out=(int8_t)a.v[AV_INTEGER_SIZE-1];
163
164 for(i= AV_INTEGER_SIZE-2; i>=0; i--){
165 out = (out<<16) + a.v[i];
166 }
167 return out;
168 }
169