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1 /*
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2 * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
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3 *
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4 * This file is part of FFmpeg.
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5 *
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6 * FFmpeg is free software; you can redistribute it and/or
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7 * modify it under the terms of the GNU Lesser General Public
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8 * License as published by the Free Software Foundation; either
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9 * version 2.1 of the License, or (at your option) any later version.
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10 *
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11 * FFmpeg is distributed in the hope that it will be useful,
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12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 * Lesser General Public License for more details.
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15 *
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16 * You should have received a copy of the GNU Lesser General Public
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17 * License along with FFmpeg; if not, write to the Free Software
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18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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19 */
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20
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21 #ifndef AVUTIL_SOFTFLOAT_H
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22 #define AVUTIL_SOFTFLOAT_H
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23
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24 #include <stdint.h>
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25 #include "common.h"
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26
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27 #include "avassert.h"
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28
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29 #define MIN_EXP -126
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30 #define MAX_EXP 126
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31 #define ONE_BITS 29
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32
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33 typedef struct SoftFloat{
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34 int32_t exp;
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35 int32_t mant;
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36 }SoftFloat;
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37
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38 static av_const SoftFloat av_normalize_sf(SoftFloat a){
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39 if(a.mant){
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40 #if 1
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41 while((a.mant + 0x20000000U)<0x40000000U){
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42 a.mant += a.mant;
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43 a.exp -= 1;
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44 }
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45 #else
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46 int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
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47 a.exp -= s;
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48 a.mant <<= s;
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49 #endif
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50 if(a.exp < MIN_EXP){
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51 a.exp = MIN_EXP;
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52 a.mant= 0;
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53 }
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54 }else{
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55 a.exp= MIN_EXP;
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56 }
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57 return a;
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58 }
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59
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60 static inline av_const SoftFloat av_normalize1_sf(SoftFloat a){
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61 #if 1
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62 if((int32_t)(a.mant + 0x40000000U) < 0){
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63 a.exp++;
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64 a.mant>>=1;
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65 }
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66 av_assert2(a.mant < 0x40000000 && a.mant > -0x40000000);
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67 return a;
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68 #elif 1
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69 int t= a.mant + 0x40000000 < 0;
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70 return (SoftFloat){a.exp+t, a.mant>>t};
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71 #else
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72 int t= (a.mant + 0x40000000U)>>31;
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73 return (SoftFloat){a.exp+t, a.mant>>t};
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74 #endif
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75 }
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76
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77 /**
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78 * @return Will not be more denormalized than a+b. So if either input is
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79 * normalized, then the output will not be worse then the other input.
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80 * If both are normalized, then the output will be normalized.
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81 */
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82 static inline av_const SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
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83 a.exp += b.exp;
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84 av_assert2((int32_t)((a.mant * (int64_t)b.mant) >> ONE_BITS) == (a.mant * (int64_t)b.mant) >> ONE_BITS);
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85 a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
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86 return av_normalize1_sf(a);
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87 }
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88
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89 /**
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90 * b has to be normalized and not zero.
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91 * @return Will not be more denormalized than a.
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92 */
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93 static av_const SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
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94 a.exp -= b.exp+1;
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95 a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
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96 return av_normalize1_sf(a);
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97 }
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98
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99 static inline av_const int av_cmp_sf(SoftFloat a, SoftFloat b){
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100 int t= a.exp - b.exp;
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101 if(t<0) return (a.mant >> (-t)) - b.mant ;
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102 else return a.mant - (b.mant >> t);
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103 }
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104
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105 static inline av_const SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
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106 int t= a.exp - b.exp;
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107 if (t <-31) return b;
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108 else if (t < 0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
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109 else if (t < 32) return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >> t )});
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110 else return a;
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111 }
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112
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113 static inline av_const SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
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114 return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
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115 }
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116
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117 //FIXME sqrt, log, exp, pow, sin, cos
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118
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119 static inline av_const SoftFloat av_int2sf(int v, int frac_bits){
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120 return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
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121 }
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122
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123 /**
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124 * Rounding is to -inf.
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125 */
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126 static inline av_const int av_sf2int(SoftFloat v, int frac_bits){
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127 v.exp += frac_bits - ONE_BITS;
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128 if(v.exp >= 0) return v.mant << v.exp ;
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129 else return v.mant >>(-v.exp);
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130 }
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131
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132 #endif /* AVUTIL_SOFTFLOAT_H */
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