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Diffstat (limited to 'libavutil/integer.c')
| -rw-r--r-- | libavutil/integer.c | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/libavutil/integer.c b/libavutil/integer.c new file mode 100644 index 0000000000..38a826f861 --- /dev/null +++ b/libavutil/integer.c @@ -0,0 +1,221 @@ +/* + * arbitrary precision integers + * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at> + * + * This library 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 of the License, or (at your option) any later version. + * + * This library 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 this library; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 |