mirror of https://github.com/axmolengine/axmol.git
71 lines
2.0 KiB
C++
71 lines
2.0 KiB
C++
|
/*
|
||
|
|
* Copyright (C) 2014 The Android Open Source Project
|
||
|
|
*
|
||
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
||
|
|
* you may not use this file except in compliance with the License.
|
||
|
|
* You may obtain a copy of the License at
|
||
|
|
*
|
||
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
||
|
|
*
|
||
|
|
* Unless required by applicable law or agreed to in writing, software
|
||
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
||
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
* See the License for the specific language governing permissions and
|
||
|
|
* limitations under the License.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <cmath>
|
||
|
|
#include "audio/android/audio_utils/include/audio_utils/minifloat.h"
|
||
|
|
|
||
|
|
#define EXPONENT_BITS 3
|
||
|
|
#define EXPONENT_MAX ((1 << EXPONENT_BITS) - 1)
|
||
|
|
#define EXCESS ((1 << EXPONENT_BITS) - 2)
|
||
|
|
|
||
|
|
#define MANTISSA_BITS 13
|
||
|
|
#define MANTISSA_MAX ((1 << MANTISSA_BITS) - 1)
|
||
|
|
#define HIDDEN_BIT (1 << MANTISSA_BITS)
|
||
|
|
#define ONE_FLOAT ((float) (1 << (MANTISSA_BITS + 1)))
|
||
|
|
|
||
|
|
#define MINIFLOAT_MAX ((EXPONENT_MAX << MANTISSA_BITS) | MANTISSA_MAX)
|
||
|
|
|
||
|
|
#if EXPONENT_BITS + MANTISSA_BITS != 16
|
||
|
|
#error EXPONENT_BITS and MANTISSA_BITS must sum to 16
|
||
|
|
#endif
|
||
|
|
|
||
|
|
extern "C" {
|
||
|
|
|
||
|
|
gain_minifloat_t gain_from_float(float v)
|
||
|
|
{
|
||
|
|
if (std::isnan(v) || v <= 0.0f)
|
||
|
|
{
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
if (v >= 2.0f)
|
||
|
|
{
|
||
|
|
return MINIFLOAT_MAX;
|
||
|
|
}
|
||
|
|
int exp;
|
||
|
|
float r = frexpf(v, &exp);
|
||
|
|
if ((exp += EXCESS) > EXPONENT_MAX)
|
||
|
|
{
|
||
|
|
return MINIFLOAT_MAX;
|
||
|
|
}
|
||
|
|
if (-exp >= MANTISSA_BITS)
|
||
|
|
{
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
int mantissa = (int) (r * ONE_FLOAT);
|
||
|
|
return exp > 0 ? (exp << MANTISSA_BITS) | (mantissa & ~HIDDEN_BIT) :
|
||
|
|
(mantissa >> (1 - exp)) & MANTISSA_MAX;
|
||
|
|
}
|
||
|
|
|
||
|
|
float float_from_gain(gain_minifloat_t a)
|
||
|
|
{
|
||
|
|
int mantissa = a & MANTISSA_MAX;
|
||
|
|
int exponent = (a >> MANTISSA_BITS) & EXPONENT_MAX;
|
||
|
|
return ldexpf((exponent > 0 ? HIDDEN_BIT | mantissa : mantissa << 1) / ONE_FLOAT,
|
||
|
|
exponent - EXCESS);
|
||
|
|
}
|
||
|
|
|
||
|
|
} // extern "C" {
|