quicktime/ffmpeg/libavcodec/integer.c

   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
  30 AVInteger 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
  40 AVInteger 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
  50 /**
  51  * returns the rounded down value of the logarithm of base 2 of the given AVInteger.
  52  * this is simply the index of the most significant bit which is 1. Or 0 of all bits are 0
  53  */
  54 int av_log2_i(AVInteger a){
  55     int i;
  56
  57     for(i=AV_INTEGER_SIZE-1; i>=0; i--){
  58         if(a.v[i])
  59             return av_log2_16bit(a.v[i]) + 16*i;
  60     }
  61     return -1;
  62 }
  63
  64 AVInteger av_mul_i(AVInteger a, AVInteger b){
  65     AVInteger out;
  66     int i, j;
  67     int na= (av_log2_i(a)+16) >> 4;
  68     int nb= (av_log2_i(b)+16) >> 4;
  69
  70     memset(&out, 0, sizeof(out));
  71
  72     for(i=0; i<na; i++){
  73         unsigned int carry=0;
  74
  75         if(a.v[i])
  76             for(j=i; j<AV_INTEGER_SIZE && j-i<=nb; j++){
  77                 carry= (carry>>16) + out.v[j] + a.v[i]*b.v[j-i];
  78                 out.v[j]= carry;
  79             }
  80     }
  81
  82     return out;
  83 }
  84
  85 /**
  86  * returns 0 if a==b, 1 if a>b and -1 if a<b.
  87  */
  88 int av_cmp_i(AVInteger a, AVInteger b){
  89     int i;
  90     int v= (int16_t)a.v[AV_INTEGER_SIZE-1] - (int16_t)b.v[AV_INTEGER_SIZE-1];
  91     if(v) return (v>>16)|1;
  92
  93     for(i=AV_INTEGER_SIZE-2; i>=0; i--){
  94         int v= a.v[i] - b.v[i];
  95         if(v) return (v>>16)|1;
  96     }
  97     return 0;
  98 }
  99
 100 /**
 101  * bitwise shift.
 102  * @param s the number of bits by which the value should be shifted right, may be negative for shifting left
 103  */
 104 AVInteger av_shr_i(AVInteger a, int s){
 105     AVInteger out;
 106     int i;
 107
 108     for(i=0; i<AV_INTEGER_SIZE; i++){
 109         int index= i + (s>>4);
 110         unsigned int v=0;
 111         if(index+1<AV_INTEGER_SIZE && index+1>=0) v = a.v[index+1]<<16;
 112         if(index  <AV_INTEGER_SIZE && index  >=0) v+= a.v[index  ];
 113         out.v[i]= v >> (s&15);
 114     }
 115     return out;
 116 }
 117
 118 /**
 119  * returns a % b.
 120  * @param quot a/b will be stored here
 121  */
 122 AVInteger av_mod_i(AVInteger *quot, AVInteger a, AVInteger b){
 123     int i= av_log2_i(a) - av_log2_i(b);
 124     AVInteger quot_temp;
 125     if(!quot) quot = &quot_temp;
 126
 127     assert((int16_t)a[AV_INTEGER_SIZE-1] >= 0 && (int16_t)b[AV_INTEGER_SIZE-1] >= 0);
 128     assert(av_log2(b)>=0);
 129
 130     if(i > 0)
 131         b= av_shr_i(b, -i);
 132
 133     memset(quot, 0, sizeof(AVInteger));
 134
 135     while(i-- >= 0){
 136         *quot= av_shr_i(*quot, -1);
 137         if(av_cmp_i(a, b) >= 0){
 138             a= av_sub_i(a, b);
 139             quot->v[0] += 1;
 140         }
 141         b= av_shr_i(b, 1);
 142     }
 143     return a;
 144 }
 145
 146 /**
 147  * returns a/b.
 148  */
 149 AVInteger av_div_i(AVInteger a, AVInteger b){
 150     AVInteger quot;
 151     av_mod_i(&quot, a, b);
 152     return quot;
 153 }
 154
 155 /**
 156  * converts the given int64_t to an AVInteger.
 157  */
 158 AVInteger av_int2i(int64_t a){
 159     AVInteger out;
 160     int i;
 161
 162     for(i=0; i<AV_INTEGER_SIZE; i++){
 163         out.v[i]= a;
 164         a>>=16;
 165     }
 166     return out;
 167 }
 168
 169 /**
 170  * converts the given AVInteger to an int64_t.
 171  * if the AVInteger is too large to fit into an int64_t,
 172  * then only the least significant 64bit will be used
 173  */
 174 int64_t av_i2int(AVInteger a){
 175     int i;
 176     int64_t out=(int8_t)a.v[AV_INTEGER_SIZE-1];
 177
 178     for(i= AV_INTEGER_SIZE-2; i>=0; i--){
 179         out = (out<<16) + a.v[i];
 180     }
 181     return out;
 182 }
 183
 184 #if 0
 185 #undef NDEBUG
 186 #include <assert.h>
 187
 188 const uint8_t ff_log2_tab[256]={
 189         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,
 190         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,
 191         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,
 192         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,
 193         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,
 194         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,
 195         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,
 196         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
 197 };
 198
 199 main(){
 200     int64_t a,b;
 201
 202     for(a=7; a<256*256*256; a+=13215){
 203         for(b=3; b<256*256*256; b+=27118){
 204             AVInteger ai= av_int2i(a);
 205             AVInteger bi= av_int2i(b);
 206
 207             assert(av_i2int(ai) == a);
 208             assert(av_i2int(bi) == b);
 209             assert(av_i2int(av_add_i(ai,bi)) == a+b);
 210             assert(av_i2int(av_sub_i(ai,bi)) == a-b);
 211             assert(av_i2int(av_mul_i(ai,bi)) == a*b);
 212             assert(av_i2int(av_shr_i(ai, 9)) == a>>9);
 213             assert(av_i2int(av_shr_i(ai,-9)) == a<<9);
 214             assert(av_i2int(av_shr_i(ai, 17)) == a>>17);
 215             assert(av_i2int(av_shr_i(ai,-17)) == a<<17);
 216             assert(av_log2_i(ai) == av_log2(a));
 217             assert(av_i2int(av_div_i(ai,bi)) == a/b);
 218         }
 219     }
 220 }
 221 #endif