a0d614bbd6f1e6847bb61ff21d78ae5761b09efa
[libav.git] / 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
26 #define MIN_EXP -126
27 #define MAX_EXP 126
28 #define ONE_BITS 29
29
30 typedef struct SoftFloat{
31 int32_t exp;
32 int32_t mant;
33 }SoftFloat;
34
35 static SoftFloat av_normalize_sf(SoftFloat a){
36 if(a.mant){
37 #if 1
38 while((a.mant + 0x20000000U)<0x40000000U){
39 a.mant += a.mant;
40 a.exp -= 1;
41 }
42 #else
43 int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
44 a.exp -= s;
45 a.mant <<= s;
46 #endif
47 if(a.exp < MIN_EXP){
48 a.exp = MIN_EXP;
49 a.mant= 0;
50 }
51 }else{
52 a.exp= MIN_EXP;
53 }
54 return a;
55 }
56
57 static inline SoftFloat av_normalize1_sf(SoftFloat a){
58 #if 1
59 if(a.mant + 0x40000000 < 0){
60 a.exp++;
61 a.mant>>=1;
62 }
63 return a;
64 #elif 1
65 int t= a.mant + 0x40000000 < 0;
66 return (SoftFloat){a.exp+t, a.mant>>t};
67 #else
68 int t= (a.mant + 0x40000000U)>>31;
69 return (SoftFloat){a.exp+t, a.mant>>t};
70 #endif
71 }
72
73 /**
74 *
75 * @return will not be more denormalized then a+b, so if either input is
76 * normalized then the output wont be worse then the other input
77 * if both are normalized then the output will be normalized
78 */
79 static inline 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 *
87 * b has to be normalized and not zero
88 * @return will not be more denormalized then a
89 */
90 static SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
91 a.exp -= b.exp+1;
92 a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
93 return av_normalize1_sf(a);
94 }
95
96 static inline int av_cmp_sf(SoftFloat a, SoftFloat b){
97 int t= a.exp - b.exp;
98 if(t<0) return (a.mant >> (-t)) - b.mant ;
99 else return a.mant - (b.mant >> t);
100 }
101
102 static inline SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
103 int t= a.exp - b.exp;
104 if(t<0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
105 else return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >> t )});
106 }
107
108 static inline SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
109 return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
110 }
111
112 //FIXME sqrt, log, exp, pow, sin, cos
113
114 static inline SoftFloat av_int2sf(int v, int frac_bits){
115 return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
116 }
117
118 /**
119 *
120 * rounding is to -inf
121 */
122 static inline int av_sf2int(SoftFloat v, int frac_bits){
123 v.exp += frac_bits - ONE_BITS;
124 if(v.exp >= 0) return v.mant << v.exp ;
125 else return v.mant >>(-v.exp);
126 }
127
128 #endif // AVUTIL_SOFTFLOAT_H