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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 #include "avassert.h"
28 
29 #define MIN_EXP -126
30 #define MAX_EXP 126
31 #define ONE_BITS 29
32 
33 typedef struct SoftFloat{
36 }SoftFloat;
37 
39  if(a.mant){
40 #if 1
41  while((a.mant + 0x20000000U)<0x40000000U){
42  a.mant += a.mant;
43  a.exp -= 1;
44  }
45 #else
46  int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
47  a.exp -= s;
48  a.mant <<= s;
49 #endif
50  if(a.exp < MIN_EXP){
51  a.exp = MIN_EXP;
52  a.mant= 0;
53  }
54  }else{
55  a.exp= MIN_EXP;
56  }
57  return a;
58 }
59 
61 #if 1
62  if((int32_t)(a.mant + 0x40000000U) < 0){
63  a.exp++;
64  a.mant>>=1;
65  }
66  av_assert2(a.mant < 0x40000000 && a.mant > -0x40000000);
67  return a;
68 #elif 1
69  int t= a.mant + 0x40000000 < 0;
70  return (SoftFloat){a.exp+t, a.mant>>t};
71 #else
72  int t= (a.mant + 0x40000000U)>>31;
73  return (SoftFloat){a.exp+t, a.mant>>t};
74 #endif
75 }
76 
77 /**
78  * @return Will not be more denormalized than a+b. So if either input is
79  * normalized, then the output will not be worse then the other input.
80  * If both are normalized, then the output will be normalized.
81  */
83  a.exp += b.exp;
84  av_assert2((int32_t)((a.mant * (int64_t)b.mant) >> ONE_BITS) == (a.mant * (int64_t)b.mant) >> ONE_BITS);
85  a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
86  return av_normalize1_sf(a);
87 }
88 
89 /**
90  * b has to be normalized and not zero.
91  * @return Will not be more denormalized than a.
92  */
94  a.exp -= b.exp+1;
95  a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
96  return av_normalize1_sf(a);
97 }
98 
99 static inline av_const int av_cmp_sf(SoftFloat a, SoftFloat b){
100  int t= a.exp - b.exp;
101  if(t<0) return (a.mant >> (-t)) - b.mant ;
102  else return a.mant - (b.mant >> t);
103 }
104 
106  int t= a.exp - b.exp;
107  if (t <-31) return b;
108  else if (t < 0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
109  else if (t < 32) return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >> t )});
110  else return a;
111 }
112 
114  return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
115 }
116 
117 //FIXME sqrt, log, exp, pow, sin, cos
118 
119 static inline av_const SoftFloat av_int2sf(int v, int frac_bits){
120  return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
121 }
122 
123 /**
124  * Rounding is to -inf.
125  */
126 static inline av_const int av_sf2int(SoftFloat v, int frac_bits){
127  v.exp += frac_bits - ONE_BITS;
128  if(v.exp >= 0) return v.mant << v.exp ;
129  else return v.mant >>(-v.exp);
130 }
131 
132 #endif /* AVUTIL_SOFTFLOAT_H */