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avutil: Softfloat implementation for IEEE 754 floating point

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Signed-off-by: Umair Khan <omerjerk@gmail.com>
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Umair Khan 2016-08-12 17:47:06 +05:30 committed by Thilo Borgmann
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commit fb1f67a70b
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libavutil/softfloat_ieee754.h Normal file
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/*
* Copyright (c) 2016 Umair Khan <omerjerk@gmail.com>
*
* 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_IEEE754_H
#define AVUTIL_SOFTFLOAT_IEEE754_H
#include <stdint.h>
#define EXP_BIAS 127
#define MANT_BITS 23
typedef struct SoftFloat_IEEE754 {
int32_t sign;
uint64_t mant;
int32_t exp;
} SoftFloat_IEEE754;
static const SoftFloat_IEEE754 FLOAT_0 = {0, 0, -126};
static const SoftFloat_IEEE754 FLOAT_1 = {0, 0, 0};
/** Normalize the softfloat as defined by IEEE 754 single-recision floating
* point specification
*/
static SoftFloat_IEEE754 av_normalize_sf_ieee754(SoftFloat_IEEE754 sf) {
while( sf.mant >= 0x1000000UL ) {
sf.exp++;
sf.mant >>= 1;
}
sf.mant &= 0x007fffffUL;
return sf;
}
/** Convert integer to softfloat.
* @return softfloat with value n * 2^e
*/
static SoftFloat_IEEE754 av_int2sf_ieee754(int64_t n, int e) {
int sign = 0;
if (n < 0) {
sign = 1;
n *= -1;
}
return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, n << MANT_BITS, 0 + e});
}
/** Make a softfloat out of the bitstream. Assumes the bits are in the form as defined
* by the IEEE 754 spec.
*/
static SoftFloat_IEEE754 av_bits2sf_ieee754(uint32_t n) {
return ((SoftFloat_IEEE754) { (n & 0x80000000UL), (n & 0x7FFFFFUL), (n & 0x7F800000UL) });
}
/** Convert the softfloat to integer
*/
static int av_sf2int_ieee754(SoftFloat_IEEE754 a) {
if(a.exp >= 0) return a.mant << a.exp ;
else return a.mant >>(-a.exp);
}
/** Divide a by b. b should not be zero.
* @return normalized result
*/
static SoftFloat_IEEE754 av_div_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
int32_t mant, exp, sign;
a = av_normalize_sf_ieee754(a);
b = av_normalize_sf_ieee754(b);
sign = a.sign ^ b.sign;
mant = ((((uint64_t) (a.mant | 0x00800000UL)) << MANT_BITS) / (b.mant| 0x00800000UL));
exp = a.exp - b.exp;
return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, mant, exp});
}
/** Multiply a with b
* #return normalized result
*/
static SoftFloat_IEEE754 av_mul_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
int32_t sign, mant, exp;
a = av_normalize_sf_ieee754(a);
b = av_normalize_sf_ieee754(b);
sign = a.sign ^ b.sign;
mant = (((uint64_t)(a.mant|0x00800000UL) * (uint64_t)(b.mant|0x00800000UL))>>MANT_BITS);
exp = a.exp + b.exp;
return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, mant, exp});
}
/** Compare a with b strictly
* @returns 1 if the a and b are equal, 0 otherwise.
*/
static int av_cmp_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
a = av_normalize_sf_ieee754(a);
b = av_normalize_sf_ieee754(b);
if (a.sign != b.sign) return 0;
if (a.mant != b.mant) return 0;
if (a.exp != b.exp ) return 0;
return 1;
}
#endif /*AVUTIL_SOFTFLOAT_IEEE754_H*/