libavutil/integer.c

   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
  31 AVInteger 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
  41 AVInteger 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
  51 int 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
  61 AVInteger 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
  82 int 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
  94 AVInteger 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
 108 AVInteger 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
 132 AVInteger av_div_i(AVInteger a, AVInteger b){
 133     AVInteger quot;
 134     av_mod_i(&quot, a, b);
 135     return quot;
 136 }
 137
 138 AVInteger 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
 149 int64_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
 163 const 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
 174 int 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