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 libavutil/integer.c
24 * arbitrary precision integers
25 * @author Michael Niedermayer <michaelni@gmx.at>
26 */
27
28#include "common.h"
29#include "integer.h"
30
31AVInteger av_add_i(AVInteger a, AVInteger b){
32    int i, carry=0;
33
34    for(i=0; i<AV_INTEGER_SIZE; i++){
35        carry= (carry>>16) + a.v[i] + b.v[i];
36        a.v[i]= carry;
37    }
38    return a;
39}
40
41AVInteger av_sub_i(AVInteger a, AVInteger b){
42    int i, carry=0;
43
44    for(i=0; i<AV_INTEGER_SIZE; i++){
45        carry= (carry>>16) + a.v[i] - b.v[i];
46        a.v[i]= carry;
47    }
48    return a;
49}
50
51int av_log2_i(AVInteger a){
52    int i;
53
54    for(i=AV_INTEGER_SIZE-1; i>=0; i--){
55        if(a.v[i])
56            return av_log2_16bit(a.v[i]) + 16*i;
57    }
58    return -1;
59}
60
61AVInteger av_mul_i(AVInteger a, AVInteger b){
62    AVInteger out;
63    int i, j;
64    int na= (av_log2_i(a)+16) >> 4;
65    int nb= (av_log2_i(b)+16) >> 4;
66
67    memset(&out, 0, sizeof(out));
68
69    for(i=0; i<na; i++){
70        unsigned int carry=0;
71
72        if(a.v[i])
73            for(j=i; j<AV_INTEGER_SIZE && j-i<=nb; j++){
74                carry= (carry>>16) + out.v[j] + a.v[i]*b.v[j-i];
75                out.v[j]= carry;
76            }
77    }
78
79    return out;
80}
81
82int av_cmp_i(AVInteger a, AVInteger b){
83    int i;
84    int v= (int16_t)a.v[AV_INTEGER_SIZE-1] - (int16_t)b.v[AV_INTEGER_SIZE-1];
85    if(v) return (v>>16)|1;
86
87    for(i=AV_INTEGER_SIZE-2; i>=0; i--){
88        int v= a.v[i] - b.v[i];
89        if(v) return (v>>16)|1;
90    }
91    return 0;
92}
93
94AVInteger av_shr_i(AVInteger a, int s){
95    AVInteger out;
96    int i;
97
98    for(i=0; i<AV_INTEGER_SIZE; i++){
99        unsigned int index= i + (s>>4);
100        unsigned int v=0;
101        if(index+1<AV_INTEGER_SIZE) v = a.v[index+1]<<16;
102        if(index  <AV_INTEGER_SIZE) v+= a.v[index  ];
103        out.v[i]= v >> (s&15);
104    }
105    return out;
106}
107
108AVInteger av_mod_i(AVInteger *quot, AVInteger a, AVInteger b){
109    int i= av_log2_i(a) - av_log2_i(b);
110    AVInteger quot_temp;
111    if(!quot) quot = &quot_temp;
112
113    assert((int16_t)a[AV_INTEGER_SIZE-1] >= 0 && (int16_t)b[AV_INTEGER_SIZE-1] >= 0);
114    assert(av_log2(b)>=0);
115
116    if(i > 0)
117        b= av_shr_i(b, -i);
118
119    memset(quot, 0, sizeof(AVInteger));
120
121    while(i-- >= 0){
122        *quot= av_shr_i(*quot, -1);
123        if(av_cmp_i(a, b) >= 0){
124            a= av_sub_i(a, b);
125            quot->v[0] += 1;
126        }
127        b= av_shr_i(b, 1);
128    }
129    return a;
130}
131
132AVInteger av_div_i(AVInteger a, AVInteger b){
133    AVInteger quot;
134    av_mod_i(&quot, a, b);
135    return quot;
136}
137
138AVInteger av_int2i(int64_t a){
139    AVInteger out;
140    int i;
141
142    for(i=0; i<AV_INTEGER_SIZE; i++){
143        out.v[i]= a;
144        a>>=16;
145    }
146    return out;
147}
148
149int64_t av_i2int(AVInteger a){
150    int i;
151    int64_t out=(int8_t)a.v[AV_INTEGER_SIZE-1];
152
153    for(i= AV_INTEGER_SIZE-2; i>=0; i--){
154        out = (out<<16) + a.v[i];
155    }
156    return out;
157}
158
159#ifdef TEST
160#undef NDEBUG
161#include <assert.h>
162
163const uint8_t ff_log2_tab[256]={
164        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,
165        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,
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        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,
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        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
172};
173
174int main(void){
175    int64_t a,b;
176
177    for(a=7; a<256*256*256; a+=13215){
178        for(b=3; b<256*256*256; b+=27118){
179            AVInteger ai= av_int2i(a);
180            AVInteger bi= av_int2i(b);
181
182            assert(av_i2int(ai) == a);
183            assert(av_i2int(bi) == b);
184            assert(av_i2int(av_add_i(ai,bi)) == a+b);
185            assert(av_i2int(av_sub_i(ai,bi)) == a-b);
186            assert(av_i2int(av_mul_i(ai,bi)) == a*b);
187            assert(av_i2int(av_shr_i(ai, 9)) == a>>9);
188            assert(av_i2int(av_shr_i(ai,-9)) == a<<9);
189            assert(av_i2int(av_shr_i(ai, 17)) == a>>17);
190            assert(av_i2int(av_shr_i(ai,-17)) == a<<17);
191            assert(av_log2_i(ai) == av_log2(a));
192            assert(av_i2int(av_div_i(ai,bi)) == a/b);
193        }
194    }
195    return 0;
196}
197#endif
198