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softfloat.h
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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{
34 }SoftFloat;
35 
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 
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  */
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  */
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 
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 
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 */