ffmpeg / libavutil / softfloat.h @ 80a289b9
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/*


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* Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>

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*

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* This file is part of FFmpeg.

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*

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* FFmpeg is free software; you can redistribute it and/or

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* modify it under the terms of the GNU Lesser General Public

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* License as published by the Free Software Foundation; either

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* version 2.1 of the License, or (at your option) any later version.

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*

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* FFmpeg is distributed in the hope that it will be useful,

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* but WITHOUT ANY WARRANTY; without even the implied warranty of

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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

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* Lesser General Public License for more details.

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*

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* You should have received a copy of the GNU Lesser General Public

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* License along with FFmpeg; if not, write to the Free Software

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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 021101301 USA

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*

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*/

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#define MIN_EXP 126 
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#define MAX_EXP 126 
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#define ONE_BITS 29 
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typedef struct SoftFloat{ 
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int32_t exp; 
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int32_t mant; 
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}SoftFloat; 
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static SoftFloat av_normalize_sf(SoftFloat a){

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if(a.mant){

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#if 1 
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while((a.mant + 0x20000000U)<0x40000000U){ 
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a.mant += a.mant; 
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a.exp = 1;

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} 
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#else

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int s=ONE_BITS + 1  av_log2(a.mant ^ (a.mant<<1)); 
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a.exp = s; 
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a.mant <<= s; 
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#endif

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if(a.exp < MIN_EXP){

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a.exp = MIN_EXP; 
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a.mant= 0;

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} 
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}else{

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a.exp= MIN_EXP; 
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} 
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return a;

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} 
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static inline SoftFloat av_normalize1_sf(SoftFloat a){ 
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#if 1 
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if(a.mant + 0x40000000 < 0){ 
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a.exp++; 
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a.mant>>=1;

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} 
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return a;

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#elif 1 
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int t= a.mant + 0x40000000 < 0; 
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return (SoftFloat){a.exp+t, a.mant>>t};

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#else

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int t= (a.mant + 0x40000000U)>>31; 
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return (SoftFloat){a.exp+t, a.mant>>t};

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#endif

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} 
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/**

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*

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* @return will not be more denormalized then a+b, so if either input is

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* normalized then the output wont be worse then the other input

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* if both are normalized then the output will be normalized

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*/

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static inline SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){ 
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a.exp += b.exp; 
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a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS; 
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return av_normalize1_sf(a);

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} 
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/**

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*

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* b has to be normalized and not zero

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* @return will not be more denormalized then a

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*/

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static SoftFloat av_div_sf(SoftFloat a, SoftFloat b){

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a.exp = b.exp+1;

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a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;

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return av_normalize1_sf(a);

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} 
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static inline int av_cmp_sf(SoftFloat a, SoftFloat b){ 
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int t= a.exp  b.exp;

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if(t<0) return (a.mant >> (t))  b.mant ; 
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else return a.mant  (b.mant >> t); 
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} 
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static inline SoftFloat av_add_sf(SoftFloat a, SoftFloat b){ 
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int t= a.exp  b.exp;

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if(t<0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (t))}); 
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else return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >> t )}); 
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} 
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static inline SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){ 
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return av_add_sf(a, (SoftFloat){b.exp, b.mant});

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} 
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//FIXME sqrt, log, exp, pow, sin, cos

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static inline SoftFloat av_int2sf(int v, int frac_bits){ 
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return av_normalize_sf((SoftFloat){ONE_BITSfrac_bits, v});

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} 
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/**

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*

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* rounding is to inf

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*/

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static inline int av_sf2int(SoftFloat v, int frac_bits){ 
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v.exp += frac_bits  ONE_BITS; 
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if(v.exp >= 0) return v.mant << v.exp ; 
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else return v.mant >>(v.exp); 
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} 