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FFmpeg/libavutil/softfloat.h

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/*
* Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVUTIL_SOFTFLOAT_H
#define AVUTIL_SOFTFLOAT_H
#include <stdint.h>
#include "common.h"
#include "avassert.h"
#include "softfloat_tables.h"
#define MIN_EXP -149
#define MAX_EXP 126
#define ONE_BITS 29
typedef struct SoftFloat{
int32_t mant;
int32_t exp;
}SoftFloat;
static const SoftFloat FLOAT_0 = { 0, MIN_EXP}; ///< 0.0
static const SoftFloat FLOAT_05 = { 0x20000000, 0}; ///< 0.5
static const SoftFloat FLOAT_1 = { 0x20000000, 1}; ///< 1.0
static const SoftFloat FLOAT_EPSILON = { 0x29F16B12, -16}; ///< A small value
static const SoftFloat FLOAT_1584893192 = { 0x32B771ED, 1}; ///< 1.584893192 (10^.2)
static const SoftFloat FLOAT_100000 = { 0x30D40000, 17}; ///< 100000
static const SoftFloat FLOAT_0999999 = { 0x3FFFFBCE, 0}; ///< 0.999999
static const SoftFloat FLOAT_MIN = { 0x20000000, MIN_EXP};
/**
* Convert a SoftFloat to a double precision float.
*/
static inline av_const double av_sf2double(SoftFloat v) {
v.exp -= ONE_BITS +1;
return ldexp(v.mant, v.exp);
}
static av_const SoftFloat av_normalize_sf(SoftFloat a){
if(a.mant){
#if 1
while((a.mant + 0x1FFFFFFFU)<0x3FFFFFFFU){
a.mant += a.mant;
a.exp -= 1;
}
#else
int s=ONE_BITS - av_log2(FFABS(a.mant));
a.exp -= s;
a.mant <<= s;
#endif
if(a.exp < MIN_EXP){
a.exp = MIN_EXP;
a.mant= 0;
}
}else{
a.exp= MIN_EXP;
}
return a;
}
static inline av_const SoftFloat av_normalize1_sf(SoftFloat a){
#if 1
if((int32_t)(a.mant + 0x40000000U) <= 0){
a.exp++;
a.mant>>=1;
}
av_assert2(a.mant < 0x40000000 && a.mant > -0x40000000);
av_assert2(a.exp <= MAX_EXP);
return a;
#elif 1
int t= a.mant + 0x40000000 < 0;
return (SoftFloat){ a.mant>>t, a.exp+t};
#else
int t= (a.mant + 0x3FFFFFFFU)>>31;
return (SoftFloat){a.mant>>t, a.exp+t};
#endif
}
/**
* @return Will not be more denormalized than a*b. So if either input is
* normalized, then the output will not be worse then the other input.
* If both are normalized, then the output will be normalized.
*/
static inline av_const SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
a.exp += b.exp;
av_assert2((int32_t)((a.mant * (int64_t)b.mant) >> ONE_BITS) == (a.mant * (int64_t)b.mant) >> ONE_BITS);
a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
a = av_normalize1_sf((SoftFloat){a.mant, a.exp - 1});
if (!a.mant || a.exp < MIN_EXP)
return FLOAT_0;
return a;
}
/**
* b has to be normalized and not zero.
* @return Will not be more denormalized than a.
*/
static inline av_const SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
int64_t temp = (int64_t)a.mant * (1<<(ONE_BITS+1));
temp /= b.mant;
a.exp -= b.exp;
a.mant = temp;
while (a.mant != temp) {
temp /= 2;
a.exp--;
a.mant = temp;
}
a = av_normalize1_sf(a);
if (!a.mant || a.exp < MIN_EXP)
return FLOAT_0;
return a;
}
/**
* Compares two SoftFloats.
* @returns < 0 if the first is less
* > 0 if the first is greater
* 0 if they are equal
*/
static inline av_const int av_cmp_sf(SoftFloat a, SoftFloat b){
int t= a.exp - b.exp;
if (t <-31) return - b.mant ;
else if (t < 0) return (a.mant >> (-t)) - b.mant ;
else if (t < 32) return a.mant - (b.mant >> t);
else return a.mant ;
}
/**
* Compares two SoftFloats.
* @returns 1 if a is greater than b, 0 otherwise
*/
static inline av_const int av_gt_sf(SoftFloat a, SoftFloat b)
{
int t= a.exp - b.exp;
if (t <-31) return 0 > b.mant ;
else if (t < 0) return (a.mant >> (-t)) > b.mant ;
else if (t < 32) return a.mant > (b.mant >> t);
else return a.mant > 0 ;
}
/**
* @returns the sum of 2 SoftFloats.
*/
static inline av_const SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
int t= a.exp - b.exp;
if (t <-31) return b;
else if (t < 0) return av_normalize_sf(av_normalize1_sf((SoftFloat){ b.mant + (a.mant >> (-t)), b.exp}));
else if (t < 32) return av_normalize_sf(av_normalize1_sf((SoftFloat){ a.mant + (b.mant >> t ), a.exp}));
else return a;
}
/**
* @returns the difference of 2 SoftFloats.
*/
static inline av_const SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
return av_add_sf(a, (SoftFloat){ -b.mant, b.exp});
}
//FIXME log, exp, pow
/**
* Converts a mantisse and exponent to a SoftFloat.
* This converts a fixed point value v with frac_bits fractional bits to a
* SoftFloat.
* @returns a SoftFloat with value v * 2^-frac_bits
*/
static inline av_const SoftFloat av_int2sf(int v, int frac_bits){
int exp_offset = 0;
if(v <= INT_MIN + 1){
exp_offset = 1;
v>>=1;
}
return av_normalize_sf(av_normalize1_sf((SoftFloat){v, ONE_BITS + 1 - frac_bits + exp_offset}));
}
/**
* Converts a SoftFloat to an integer.
* Rounding is to -inf.
*/
static inline av_const int av_sf2int(SoftFloat v, int frac_bits){
v.exp += frac_bits - (ONE_BITS + 1);
if(v.exp >= 0) return v.mant << v.exp ;
else return v.mant >>(-v.exp);
}
/**
* Rounding-to-nearest used.
*/
static av_always_inline SoftFloat av_sqrt_sf(SoftFloat val)
{
int tabIndex, rem;
if (val.mant == 0)
val.exp = MIN_EXP;
else if (val.mant < 0)
abort();
else
{
tabIndex = (val.mant - 0x20000000) >> 20;
rem = val.mant & 0xFFFFF;
val.mant = (int)(((int64_t)av_sqrttbl_sf[tabIndex] * (0x100000 - rem) +
(int64_t)av_sqrttbl_sf[tabIndex + 1] * rem +
0x80000) >> 20);
val.mant = (int)(((int64_t)av_sqr_exp_multbl_sf[val.exp & 1] * val.mant +
0x10000000) >> 29);
if (val.mant < 0x40000000)
val.exp -= 2;
else
val.mant >>= 1;
val.exp = (val.exp >> 1) + 1;
}
return val;
}
/**
* Rounding-to-nearest used.
*/
static av_unused void av_sincos_sf(int a, int *s, int *c)
{
int idx, sign;
int sv, cv;
int st, ct;
idx = a >> 26;
sign = (int32_t)((unsigned)idx << 27) >> 31;
cv = av_costbl_1_sf[idx & 0xf];
cv = (cv ^ sign) - sign;
idx -= 8;
sign = (int32_t)((unsigned)idx << 27) >> 31;
sv = av_costbl_1_sf[idx & 0xf];
sv = (sv ^ sign) - sign;
idx = a >> 21;
ct = av_costbl_2_sf[idx & 0x1f];
st = av_sintbl_2_sf[idx & 0x1f];
idx = (int)(((int64_t)cv * ct - (int64_t)sv * st + 0x20000000) >> 30);
sv = (int)(((int64_t)cv * st + (int64_t)sv * ct + 0x20000000) >> 30);
cv = idx;
idx = a >> 16;
ct = av_costbl_3_sf[idx & 0x1f];
st = av_sintbl_3_sf[idx & 0x1f];
idx = (int)(((int64_t)cv * ct - (int64_t)sv * st + 0x20000000) >> 30);
sv = (int)(((int64_t)cv * st + (int64_t)sv * ct + 0x20000000) >> 30);
cv = idx;
idx = a >> 11;
ct = (int)(((int64_t)av_costbl_4_sf[idx & 0x1f] * (0x800 - (a & 0x7ff)) +
(int64_t)av_costbl_4_sf[(idx & 0x1f)+1]*(a & 0x7ff) +
0x400) >> 11);
st = (int)(((int64_t)av_sintbl_4_sf[idx & 0x1f] * (0x800 - (a & 0x7ff)) +
(int64_t)av_sintbl_4_sf[(idx & 0x1f) + 1] * (a & 0x7ff) +
0x400) >> 11);
*c = (int)(((int64_t)cv * ct + (int64_t)sv * st + 0x20000000) >> 30);
*s = (int)(((int64_t)cv * st + (int64_t)sv * ct + 0x20000000) >> 30);
}
#endif /* AVUTIL_SOFTFLOAT_H */