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ffmpeg / libavutil / softfloat.h @ 0b006599

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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 02110-1301 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_BITS-frac_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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}