src/util/fixed_point.h

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/*
 * fixed_point.h
 *
 * Copyright 2011 Pieter Agten
 *
 * This file is part of Yarf.
 *
 * Yarf is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Yarf 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Yarf.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef FIXED_POINT_H
#define FIXED_POINT_H

#include <stdint.h>

#define NB_FRACTIONAL_BITS     16

#define FRACTIONAL_MULTIPLIER  65536.0f

#define FXP_16U16_MAX       UINT32_MAX

#define FXP_16U16_ZERO      0

#define FXP_16U16_ONE       ((fxp16u16_t)1 << NB_FRACTIONAL_BITS)

#define FXP_16U16_ONE_HALF  (FXP_16U16_ONE >> 1)

typedef uint32_t fxp16u16_t;


inline uint16_t
fxp16u16_to_uint16(fxp16u16_t x)
{
  return (x + FXP_16U16_ONE_HALF) >> NB_FRACTIONAL_BITS;
}

inline float
fxp16u16_to_float(fxp16u16_t x)
{
  return ((float)x / FRACTIONAL_MULTIPLIER);
}

inline fxp16u16_t
fxp16u16_from_uint16(uint16_t x)
{
  return ((fxp16u16_t)x) << NB_FRACTIONAL_BITS;
}

inline fxp16u16_t
fxp16u16_from_float(float x)
{
  return (fxp16u16_t)((x * FRACTIONAL_MULTIPLIER) + 0.5f);
}


inline fxp16u16_t
fxp16u16_from_float_s(float x)
{
  if (x >= fxp16u16_to_float(FXP_16U16_MAX)) {
    return FXP_16U16_MAX;
  } else if (x < 0) {
    return FXP_16U16_ZERO;
  } else {
    return fxp16u16_from_float(x);
  }
}


inline fxp16u16_t
fxp16u16_mul(fxp16u16_t x, fxp16u16_t y)
{
  uint64_t result = ((uint64_t)x * (uint64_t)y);
  result += FXP_16U16_ONE_HALF;
  return (fxp16u16_t)(result >> NB_FRACTIONAL_BITS);
}

inline fxp16u16_t
fxp16u16_div(fxp16u16_t x, fxp16u16_t y)
{
  uint64_t temp = (uint64_t)x << NB_FRACTIONAL_BITS;
  temp += (y >> 1); // For correct rounding
  return (fxp16u16_t)(temp / y);
}

inline fxp16u16_t
fxp16u16_div_uint16(fxp16u16_t x, uint16_t y)
{
  uint64_t temp = (uint64_t)x;
  temp += (y >> 1); // For correct rounding
  return (fxp16u16_t)(temp / y);
}

inline fxp16u16_t
fxp16u16_square(fxp16u16_t x)
{
  return fxp16u16_mul(x,x);
}

#endif //FIXED_POINT_H