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[libav.git] / libavutil / softfloat.h
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1/*
2 * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 *
18 */
a2fd6043
MN
19
20#define MIN_EXP -126
21#define MAX_EXP 126
22#define ONE_BITS 29
23
24typedef struct SoftFloat{
25 int32_t exp;
26 int32_t mant;
27}SoftFloat;
28
29static SoftFloat av_normalize_sf(SoftFloat a){
30 if(a.mant){
31#if 1
32 while((a.mant + 0x20000000U)<0x40000000U){
33 a.mant += a.mant;
34 a.exp -= 1;
35 }
36#else
37 int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
38 a.exp -= s;
39 a.mant <<= s;
40#endif
41 if(a.exp < MIN_EXP){
42 a.exp = MIN_EXP;
43 a.mant= 0;
44 }
45 }else{
46 a.exp= MIN_EXP;
47 }
48 return a;
49}
50
51static inline SoftFloat av_normalize1_sf(SoftFloat a){
52#if 1
53 if(a.mant + 0x40000000 < 0){
54 a.exp++;
55 a.mant>>=1;
56 }
57 return a;
58#elif 1
59 int t= a.mant + 0x40000000 < 0;
60 return (SoftFloat){a.exp+t, a.mant>>t};
61#else
62 int t= (a.mant + 0x40000000U)>>31;
63 return (SoftFloat){a.exp+t, a.mant>>t};
64#endif
65}
66
67/**
68 *
69 * @return will not be more denormalized then a+b, so if either input is
70 * normalized then the output wont be worse then the other input
71 * if both are normalized then the output will be normalized
72 */
73static inline SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
74 a.exp += b.exp;
75 a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
76 return av_normalize1_sf(a);
77}
78
79/**
80 *
81 * b has to be normalized and not zero
82 * @return will not be more denormalized then a
83 */
84static SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
85 a.exp -= b.exp+1;
86 a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
87 return av_normalize1_sf(a);
88}
89
90static inline int av_cmp_sf(SoftFloat a, SoftFloat b){
91 int t= a.exp - b.exp;
92 if(t<0) return (a.mant >> (-t)) - b.mant ;
93 else return a.mant - (b.mant >> t);
94}
95
96static inline SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
97 int t= a.exp - b.exp;
98 if(t<0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
99 else return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >> t )});
100}
101
102static inline SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
103 return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
104}
105
106//FIXME sqrt, log, exp, pow, sin, cos
107
108static inline SoftFloat av_int2sf(int v, int frac_bits){
109 return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
110}
111
112/**
113 *
114 * rounding is to -inf
115 */
116static inline int av_sf2int(SoftFloat v, int frac_bits){
117 v.exp += frac_bits - ONE_BITS;
118 if(v.exp >= 0) return v.mant << v.exp ;
119 else return v.mant >>(-v.exp);
120}