libavutil/softfloat.h

   1 /*
   2  * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #ifndef AVUTIL_SOFTFLOAT_H
  22 #define AVUTIL_SOFTFLOAT_H
  23
  24 #include <stdint.h>
  25 #include "common.h"
  26
  27 #define MIN_EXP -126
  28 #define MAX_EXP  126
  29 #define ONE_BITS 29
  30
  31 typedef struct SoftFloat{
  32     int32_t  exp;
  33     int32_t mant;
  34 }SoftFloat;
  35
  36 static av_const SoftFloat av_normalize_sf(SoftFloat a){
  37     if(a.mant){
  38 #if 1
  39         while((a.mant + 0x20000000U)<0x40000000U){
  40             a.mant += a.mant;
  41             a.exp  -= 1;
  42         }
  43 #else
  44         int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
  45         a.exp   -= s;
  46         a.mant <<= s;
  47 #endif
  48         if(a.exp < MIN_EXP){
  49             a.exp = MIN_EXP;
  50             a.mant= 0;
  51         }
  52     }else{
  53         a.exp= MIN_EXP;
  54     }
  55     return a;
  56 }
  57
  58 static inline av_const SoftFloat av_normalize1_sf(SoftFloat a){
  59 #if 1
  60     if(a.mant + 0x40000000 < 0){
  61         a.exp++;
  62         a.mant>>=1;
  63     }
  64     return a;
  65 #elif 1
  66     int t= a.mant + 0x40000000 < 0;
  67     return (SoftFloat){a.exp+t, a.mant>>t};
  68 #else
  69     int t= (a.mant + 0x40000000U)>>31;
  70     return (SoftFloat){a.exp+t, a.mant>>t};
  71 #endif
  72 }
  73
  74 /**
  75  * @return Will not be more denormalized than a+b. So if either input is
  76  *         normalized, then the output will not be worse then the other input.
  77  *         If both are normalized, then the output will be normalized.
  78  */
  79 static inline av_const SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
  80     a.exp += b.exp;
  81     a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
  82     return av_normalize1_sf(a);
  83 }
  84
  85 /**
  86  * b has to be normalized and not zero.
  87  * @return Will not be more denormalized than a.
  88  */
  89 static av_const SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
  90     a.exp -= b.exp+1;
  91     a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
  92     return av_normalize1_sf(a);
  93 }
  94
  95 static inline av_const int av_cmp_sf(SoftFloat a, SoftFloat b){
  96     int t= a.exp - b.exp;
  97     if(t<0) return (a.mant >> (-t)) -  b.mant      ;
  98     else    return  a.mant          - (b.mant >> t);
  99 }
 100
 101 static inline av_const SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
 102     int t= a.exp - b.exp;
 103     if(t<0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
 104     else    return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >>   t )});
 105 }
 106
 107 static inline av_const SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
 108     return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
 109 }
 110
 111 //FIXME sqrt, log, exp, pow, sin, cos
 112
 113 static inline av_const SoftFloat av_int2sf(int v, int frac_bits){
 114     return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
 115 }
 116
 117 /**
 118  * Rounding is to -inf.
 119  */
 120 static inline av_const int av_sf2int(SoftFloat v, int frac_bits){
 121     v.exp += frac_bits - ONE_BITS;
 122     if(v.exp >= 0) return v.mant <<  v.exp ;
 123     else           return v.mant >>(-v.exp);
 124 }
 125
 126 #endif /* AVUTIL_SOFTFLOAT_H */