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
31typedef struct SoftFloat{
32    int32_t  exp;
33    int32_t mant;
34}SoftFloat;
35
36static av_const SoftFloat av_normalize_sf(SoftFloat a){
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
58static inline av_const SoftFloat av_normalize1_sf(SoftFloat a){
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 */
79static inline av_const 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 * b has to be normalized and not zero.
87 * @return Will not be more denormalized than a.
88 */
89static av_const SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
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
95static 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
101static inline av_const SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
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
107static inline av_const SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
108    return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
109}
110
111//FIXME sqrt, log, exp, pow, sin, cos
112
113static 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 */
120static 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 */
127