ADSR.h

//
//  ADRS.h
//
//  Created by Nigel Redmon on 12/18/12.
//  EarLevel Engineering: earlevel.com
//  Copyright 2012 Nigel Redmon
//
//  For a complete explanation of the ADSR envelope generator and code,
//  read the series of articles by the author, starting here:
//  http://www.earlevel.com/main/2013/06/01/envelope-generators/
//
//  License:
//
//  This source code is provided as is, without warranty.
//  You may copy and distribute verbatim copies of this document.
//  You may modify and use this source code to create binary code for your own purposes, free or commercial.
//

#pragma once

#include <stdio.h>
#include <string>

enum envState {
        env_idle = 0,
        env_attack,
        env_decay,
        env_sustain,
        env_release
};

class ADSR {
public:
        ADSR(void);
        ~ADSR(void);
        float process(void);
        float process(int sampleCount);
    float getOutput(void);
    int getState(void);
        void gate(int on);
    void setAttackRate(float rate);
    void setDecayRate(float rate);
    void setReleaseRate(float rate);
        void setSustainLevel(float level);
    void setTargetRatioA(float targetRatio);
    void setTargetRatioDR(float targetRatio);
    void reset(void);

protected:
        int state;
        float output;
        float attackRate;
        float decayRate;
        float releaseRate;
        float attackCoef;
        float decayCoef;
        float releaseCoef;
        float sustainLevel;
    float targetRatioA;
    float targetRatioDR;
    float attackBase;
    float decayBase;
    float releaseBase;
    std::string name;
    float calcCoef(float rate, float targetRatio);
};

inline float ADSR::process() {
        switch (state) {
        case env_idle:
            break;
        case env_attack:
            output = attackBase + output * attackCoef;
            if (output >= 1.0) {
                output = 1.0;
                state = env_decay;
            }
            break;
        case env_decay:
            output = decayBase + output * decayCoef;
            if (output <= sustainLevel) {
                output = sustainLevel;
                state = env_sustain;
            }
            break;
        case env_sustain:
            break;
        case env_release:
            output = releaseBase + output * releaseCoef;
            if (output <= 0.0) {
                output = 0.0;
                state = env_idle;
            }
            break;
        }
        return output;
}

inline float ADSR::process(int sampleCount)
{
        float retVal = 0;

        if(state != env_idle)
        {
                for(int i=0; i<sampleCount; i++)
                        retVal = process();
        }

        return retVal;
}

inline void ADSR::gate(int gate) {

        if (gate)
                state = env_attack;
        else if (state != env_idle)
        state = env_release;
}

inline int ADSR::getState() {
    return state;
}

inline void ADSR::reset() {
    state = env_idle;
    output = 0.0;
}

inline float ADSR::getOutput() {
        return output;
}