juce_ADSR.h

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
//==============================================================================
class JUCE_API  ADSR
{
public:
    //==============================================================================
    ADSR()
    {
        recalculateRates();
    }
 
    //==============================================================================
    struct JUCE_API  Parameters
    {
        Parameters() = default;
 
        Parameters (float attackTimeSeconds,
                    float decayTimeSeconds,
                    float sustainLevel,
                    float releaseTimeSeconds)
            : attack (attackTimeSeconds),
              decay (decayTimeSeconds),
              sustain (sustainLevel),
              release (releaseTimeSeconds)
        {
        }
 
        float attack = 0.1f, decay = 0.1f, sustain = 1.0f, release = 0.1f;
    };
 
    void setParameters (const Parameters& newParameters)
    {
        // need to call setSampleRate() first!
        jassert (sampleRate > 0.0);
 
        parameters = newParameters;
        recalculateRates();
    }
 
    const Parameters& getParameters() const noexcept  { return parameters; }
 
    bool isActive() const noexcept                    { return state != State::idle; }
 
    //==============================================================================
    void setSampleRate (double newSampleRate) noexcept
    {
        jassert (newSampleRate > 0.0);
        sampleRate = newSampleRate;
    }
 
    //==============================================================================
    void reset() noexcept
    {
        envelopeVal = 0.0f;
        state = State::idle;
    }
 
    void noteOn() noexcept
    {
        if (attackRate > 0.0f)
        {
            state = State::attack;
        }
        else if (decayRate > 0.0f)
        {
            envelopeVal = 1.0f;
            state = State::decay;
        }
        else
        {
            envelopeVal = parameters.sustain;
            state = State::sustain;
        }
    }
 
    void noteOff() noexcept
    {
        if (state != State::idle)
        {
            if (parameters.release > 0.0f)
            {
                releaseRate = (float) (envelopeVal / (parameters.release * sampleRate));
                state = State::release;
            }
            else
            {
                reset();
            }
        }
    }
 
    //==============================================================================
    float getNextSample() noexcept
    {
        switch (state)
        {
            case State::idle:
            {
                return 0.0f;
            }
 
            case State::attack:
            {
                envelopeVal += attackRate;
 
                if (envelopeVal >= 1.0f)
                {
                    envelopeVal = 1.0f;
                    goToNextState();
                }
 
                break;
            }
 
            case State::decay:
            {
                envelopeVal -= decayRate;
 
                if (envelopeVal <= parameters.sustain)
                {
                    envelopeVal = parameters.sustain;
                    goToNextState();
                }
 
                break;
            }
 
            case State::sustain:
            {
                envelopeVal = parameters.sustain;
                break;
            }
 
            case State::release:
            {
                envelopeVal -= releaseRate;
 
                if (envelopeVal <= 0.0f)
                    goToNextState();
 
                break;
            }
        }
 
        return envelopeVal;
    }
 
    template <typename FloatType>
    void applyEnvelopeToBuffer (AudioBuffer<FloatType>& buffer, int startSample, int numSamples)
    {
        jassert (startSample + numSamples <= buffer.getNumSamples());
 
        if (state == State::idle)
        {
            buffer.clear (startSample, numSamples);
            return;
        }
 
        if (state == State::sustain)
        {
            buffer.applyGain (startSample, numSamples, parameters.sustain);
            return;
        }
 
        auto numChannels = buffer.getNumChannels();
 
        while (--numSamples >= 0)
        {
            auto env = getNextSample();
 
            for (int i = 0; i < numChannels; ++i)
                buffer.getWritePointer (i)[startSample] *= env;
 
            ++startSample;
        }
    }
 
private:
    //==============================================================================
    void recalculateRates() noexcept
    {
        auto getRate = [] (float distance, float timeInSeconds, double sr)
        {
            return timeInSeconds > 0.0f ? (float) (distance / (timeInSeconds * sr)) : -1.0f;
        };
 
        attackRate  = getRate (1.0f, parameters.attack, sampleRate);
        decayRate   = getRate (1.0f - parameters.sustain, parameters.decay, sampleRate);
        releaseRate = getRate (parameters.sustain, parameters.release, sampleRate);
 
        if ((state == State::attack && attackRate <= 0.0f)
            || (state == State::decay && (decayRate <= 0.0f || envelopeVal <= parameters.sustain))
            || (state == State::release && releaseRate <= 0.0f))
        {
            goToNextState();
        }
    }
 
    void goToNextState() noexcept
    {
        if (state == State::attack)
        {
            state = (decayRate > 0.0f ? State::decay : State::sustain);
            return;
        }
 
        if (state == State::decay)
        {
            state = State::sustain;
            return;
        }
 
        if (state == State::release)
            reset();
    }
 
    //==============================================================================
    enum class State { idle, attack, decay, sustain, release };
 
    State state = State::idle;
    Parameters parameters;
 
    double sampleRate = 44100.0;
    float envelopeVal = 0.0f, attackRate = 0.0f, decayRate = 0.0f, releaseRate = 0.0f;
};
 
} // namespace juce