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/*
* arbitrary precision integers
* Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
/**
* @file integer.c
* arbitrary precision integers.
* @author Michael Niedermayer <michaelni@gmx.at>
*/
#include "common.h"
#include "integer.h"
AVInteger av_add_i(AVInteger a, AVInteger b){
int i, carry=0;
for(i=0; i<AV_INTEGER_SIZE; i++){
carry= (carry>>16) + a.v[i] + b.v[i];
a.v[i]= carry;
}
return a;
}
AVInteger av_sub_i(AVInteger a, AVInteger b){
int i, carry=0;
for(i=0; i<AV_INTEGER_SIZE; i++){
carry= (carry>>16) + a.v[i] - b.v[i];
a.v[i]= carry;
}
return a;
}
/**
* returns the rounded down value of the logarithm of base 2 of the given AVInteger.
* this is simply the index of the most significant bit which is 1. Or 0 of all bits are 0
*/
int av_log2_i(AVInteger a){
int i;
for(i=AV_INTEGER_SIZE-1; i>=0; i--){
if(a.v[i])
return av_log2_16bit(a.v[i]) + 16*i;
}
return -1;
}
AVInteger av_mul_i(AVInteger a, AVInteger b){
AVInteger out;
int i, j;
int na= (av_log2_i(a)+16) >> 4;
int nb= (av_log2_i(b)+16) >> 4;
memset(&out, 0, sizeof(out));
for(i=0; i<na; i++){
unsigned int carry=0;
if(a.v[i])
for(j=i; j<AV_INTEGER_SIZE && j-i<=nb; j++){
carry= (carry>>16) + out.v[j] + a.v[i]*b.v[j-i];
out.v[j]= carry;
}
}
return out;
}
/**
* returns 0 if a==b, 1 if a>b and -1 if a<b.
*/
int av_cmp_i(AVInteger a, AVInteger b){
int i;
int v= (int16_t)a.v[AV_INTEGER_SIZE-1] - (int16_t)b.v[AV_INTEGER_SIZE-1];
if(v) return (v>>16)|1;
for(i=AV_INTEGER_SIZE-2; i>=0; i--){
int v= a.v[i] - b.v[i];
if(v) return (v>>16)|1;
}
return 0;
}
/**
* bitwise shift.
* @param s the number of bits by which the value should be shifted right, may be negative for shifting left
*/
AVInteger av_shr_i(AVInteger a, int s){
AVInteger out;
int i;
for(i=0; i<AV_INTEGER_SIZE; i++){
int index= i + (s>>4);
unsigned int v=0;
if(index+1<AV_INTEGER_SIZE && index+1>=0) v = a.v[index+1]<<16;
if(index <AV_INTEGER_SIZE && index >=0) v+= a.v[index ];
out.v[i]= v >> (s&15);
}
return out;
}
AVInteger av_mod_i(AVInteger *quot, AVInteger a, AVInteger b){
int i= av_log2_i(a) - av_log2_i(b);
AVInteger quot_temp;
if(!quot) quot = "_temp;
assert((int16_t)a[AV_INTEGER_SIZE-1] >= 0 && (int16_t)b[AV_INTEGER_SIZE-1] >= 0);
assert(av_log2(b)>=0);
if(i > 0)
b= av_shr_i(b, -i);
memset(quot, 0, sizeof(AVInteger));
while(i-- >= 0){
*quot= av_shr_i(*quot, -1);
if(av_cmp_i(a, b) >= 0){
a= av_sub_i(a, b);
quot->v[0] += 1;
}
b= av_shr_i(b, 1);
}
return a;
}
AVInteger av_div_i(AVInteger a, AVInteger b){
AVInteger quot;
av_mod_i(", a, b);
return quot;
}
/**
* converts the given int64_t to an AVInteger.
*/
AVInteger av_int2i(int64_t a){
AVInteger out;
int i;
for(i=0; i<AV_INTEGER_SIZE; i++){
out.v[i]= a;
a>>=16;
}
return out;
}
/**
* converts the given AVInteger to an int64_t.
* if the AVInteger is too large to fit into an int64_t,
* then only the least significant 64bit will be used
*/
int64_t av_i2int(AVInteger a){
int i;
int64_t out=(int8_t)a.v[AV_INTEGER_SIZE-1];
for(i= AV_INTEGER_SIZE-2; i>=0; i--){
out = (out<<16) + a.v[i];
}
return out;
}
#if 0
#undef NDEBUG
#include <assert.h>
const uint8_t ff_log2_tab[256]={
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,
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,
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,
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,
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,
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,
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,
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
};
main(){
int64_t a,b;
for(a=7; a<256*256*256; a+=13215){
for(b=3; b<256*256*256; b+=27118){
AVInteger ai= av_int2i(a);
AVInteger bi= av_int2i(b);
assert(av_i2int(ai) == a);
assert(av_i2int(bi) == b);
assert(av_i2int(av_add_i(ai,bi)) == a+b);
assert(av_i2int(av_sub_i(ai,bi)) == a-b);
assert(av_i2int(av_mul_i(ai,bi)) == a*b);
assert(av_i2int(av_shr_i(ai, 9)) == a>>9);
assert(av_i2int(av_shr_i(ai,-9)) == a<<9);
assert(av_i2int(av_shr_i(ai, 17)) == a>>17);
assert(av_i2int(av_shr_i(ai,-17)) == a<<17);
assert(av_log2_i(ai) == av_log2(a));
assert(av_i2int(av_div_i(ai,bi)) == a/b);
}
}
}
#endif
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