422c1b3d6d617e2ff4ae79b20e6ccb5cddc70a02
[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
22 #include <stdint.h>
23
24 #define MIN_EXP -126
25 #define MAX_EXP 126
26 #define ONE_BITS 29
27
28 typedef struct SoftFloat{
29 int32_t exp;
30 int32_t mant;
31 }SoftFloat;
32
33 static SoftFloat av_normalize_sf(SoftFloat a){
34 if(a.mant){
35 #if 1
36 while((a.mant + 0x20000000U)<0x40000000U){
37 a.mant += a.mant;
38 a.exp -= 1;
39 }
40 #else
41 int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
42 a.exp -= s;
43 a.mant <<= s;
44 #endif
45 if(a.exp < MIN_EXP){
46 a.exp = MIN_EXP;
47 a.mant= 0;
48 }
49 }else{
50 a.exp= MIN_EXP;
51 }
52 return a;
53 }
54
55 static inline SoftFloat av_normalize1_sf(SoftFloat a){
56 #if 1
57 if(a.mant + 0x40000000 < 0){
58 a.exp++;
59 a.mant>>=1;
60 }
61 return a;
62 #elif 1
63 int t= a.mant + 0x40000000 < 0;
64 return (SoftFloat){a.exp+t, a.mant>>t};
65 #else
66 int t= (a.mant + 0x40000000U)>>31;
67 return (SoftFloat){a.exp+t, a.mant>>t};
68 #endif
69 }
70
71 /**
72 *
73 * @return will not be more denormalized then a+b, so if either input is
74 * normalized then the output wont be worse then the other input
75 * if both are normalized then the output will be normalized
76 */
77 static inline SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
78 a.exp += b.exp;
79 a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
80 return av_normalize1_sf(a);
81 }
82
83 /**
84 *
85 * b has to be normalized and not zero
86 * @return will not be more denormalized then a
87 */
88 static SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
89 a.exp -= b.exp+1;
90 a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
91 return av_normalize1_sf(a);
92 }
93
94 static inline int av_cmp_sf(SoftFloat a, SoftFloat b){
95 int t= a.exp - b.exp;
96 if(t<0) return (a.mant >> (-t)) - b.mant ;
97 else return a.mant - (b.mant >> t);
98 }
99
100 static inline SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
101 int t= a.exp - b.exp;
102 if(t<0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
103 else return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >> t )});
104 }
105
106 static inline SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
107 return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
108 }
109
110 //FIXME sqrt, log, exp, pow, sin, cos
111
112 static inline SoftFloat av_int2sf(int v, int frac_bits){
113 return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
114 }
115
116 /**
117 *
118 * rounding is to -inf
119 */
120 static inline 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 }