/* * 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; } /** * returns a % b. * @param quot a/b will be stored here */ 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; } /** * returns a/b. */ 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