Collidoscope

/*

 Copyright (C) 2016  Queen Mary University of London

 Author: Fiore Martin, based on CCRMA STK ADSR.h (https://ccrma.stanford.edu/software/stk/classstk_1_1ADSR.html)

 This file is part of Collidoscope.

 Collidoscope 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.

 This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

 This file incorporates work covered by the following copyright and permission notice:

    The Synthesis ToolKit in C++ (STK)

    Copyright (c) 1995--2016 Perry R. Cook and Gary P. Scavone

    Permission is hereby granted, free of charge, to any person obtaining

    a copy of this software and associated documentation files (the

    "Software"), to deal in the Software without restriction, including

    without limitation the rights to use, copy, modify, merge, publish,

    distribute, sublicense, and/or sell copies of the Software, and to

    permit persons to whom the Software is furnished to do so, subject to

    the following conditions:

    The above copyright notice and this permission notice shall be

    included in all copies or substantial portions of the Software.

    Any person wishing to distribute modifications to the Software is

    asked to send the modifications to the original developer so that they

    can be incorporated into the canonical version.  This is, however, not

    a binding provision of this license.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR

    ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF

    CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

    WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

*/

#pragma once

namespace collidoscope {

/*

 * An ASR envelope with linear shape. It is modeled after the STK envelope classes.

 * The tick() method advances the computation of the envelope one sample and returns the computed sample

 * The class is templated for the type of the samples that each tick of the envelope produces.

 *

 * Client classes can set/get the current state of the envelope with the

 * respective getter/setter methods

 *

 */

template <typename T>

class EnvASR

{

public:

    /** Possible states of the envelope. Idle means the envelope ouputs 0 */

    enum class State {

        eAttack,

        eSustain,

        eRelease,

        eIdle // before attack after release

    };

    EnvASR( T sustainLevel, T attackTime, T releaseTime, std::size_t sampleRate ) :

        mSustainLevel( sustainLevel ),

        mState( State::eIdle ),

        mValue( 0 )

    {

        if ( attackTime <= 0 )

            attackTime = T( 0.001 );

        if ( releaseTime <= 0 )

            releaseTime = T( 0.001 );

        mAttackRate =  T( 1.0 ) / (attackTime * sampleRate);

        mReleaseRate = T( 1.0 ) / (releaseTime * sampleRate);

    }

    /** Produces one sample worth of envelope */

    T tick()

    {

        switch ( mState )

        {

        case State::eIdle: {

            mValue = 0;

        };

            break;

        case State::eAttack: {

            mValue += mAttackRate;

            if ( mValue >= mSustainLevel ){

                mValue = mSustainLevel;

                mState = State::eSustain;

            }

        };

            break;

        case State::eRelease:

            mValue -= mReleaseRate;

            if ( mValue <= 0 ){

                mValue = 0;

                mState = State::eIdle;

            }

            break;

        default:

            break;

        }

        return mValue;

    }

    State getState() const

    {

        return mState;

    }

    void setState( State state )

    {

        mState = state;

    }

private:

    T mSustainLevel;

    T mAttackRate;

    T mReleaseRate;

    // output

    T mValue;

    State mState;

};

}