math.h

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/*
 * Copyright 2015 Simon Gansen
 *
 * This file is part of the uMIDI firmware.
 *
 * the uMIDI firmware 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.
 *
 * the uMIDI firmware 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 the uMIDI firmware.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef _MATH_H
#define _MATH_H

//---------------- includes -----------------//
#include <stdbool.h>
#include <stdint.h>

#include "midi.h"


//---------------- constants ----------------//
#define FIXED_POINT     16


//---------------- data types ---------------//
typedef uint32_t        fixed_t;

typedef uint64_t        fixed_accu_t;

struct linear_range
{
    uint16_t    from;       
    uint16_t    to;         
    fixed_t     slope;      
};


//---------------- prototypes ----------------//

void init_linear_from_midi(struct linear_range* config);

void init_linear_to_midi(struct linear_range* config);

uint16_t linear_from_midi(const struct linear_range* config, midi_value_t midi_value);

midi_value_t linear_to_midi(const struct linear_range* config, uint16_t input);


//---------------- inline functions ----------------//

static inline fixed_t fixed_from_int(const uint16_t value)
{
    fixed_t result = value;
    result <<= FIXED_POINT;
    return result;
}

static inline fixed_t fixed_div(const fixed_t a, const fixed_t b)
{
    fixed_accu_t accu = a;
    accu <<= FIXED_POINT;
    accu /= b;
    return (fixed_t) accu;
}

static inline fixed_t fixed_mpy(const fixed_t a, const fixed_t b)
{
    fixed_accu_t accu = a;
    accu *= b;
    accu >>= FIXED_POINT;
    return (fixed_t) accu;
}

static inline uint16_t fixed_to_int(fixed_t value)
{
    // Round
    if (value & 0x00008000) {
        value += 0x00008000;
    }

    // Drop fracional part
    value >>= FIXED_POINT;
    return (uint16_t) value;
}

#endif // _MATH_H