JUCE/modules/juce_audio_basics/effects/juce_LinearSmoothedValue.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2016 - ROLI Ltd.

   Permission is granted to use this software 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.

   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.

   -----------------------------------------------------------------------------

   To release a closed-source product which uses other parts of JUCE not
   licensed under the ISC terms, commercial licenses are available: visit
   www.juce.com for more information.

  ==============================================================================
*/

#pragma once


//==============================================================================
/**
    Utility class for linearly smoothed values like volume etc. that should
    not change abruptly but as a linear ramp, to avoid audio glitches.
*/

//==============================================================================
template <typename FloatType>
class LinearSmoothedValue
{
public:
    /** Constructor. */
    LinearSmoothedValue() noexcept
        : currentValue (0), target (0), step (0), countdown (0), stepsToTarget (0)
    {
    }

    /** Constructor. */
    LinearSmoothedValue (FloatType initialValue) noexcept
        : currentValue (initialValue), target (initialValue), step (0), countdown (0), stepsToTarget (0)
    {
    }

    //==============================================================================
    /** Reset to a new sample rate and ramp length. */
    void reset (double sampleRate, double rampLengthInSeconds) noexcept
    {
        jassert (sampleRate > 0 && rampLengthInSeconds >= 0);
        stepsToTarget = (int) std::floor (rampLengthInSeconds * sampleRate);
        currentValue = target;
        countdown = 0;
    }

    /** Set a new target value. */
    void setValue (FloatType newValue) noexcept
    {
        if (target != newValue)
        {
            target = newValue;
            countdown = stepsToTarget;

            if (countdown <= 0)
                currentValue = target;
            else
                step = (target - currentValue) / (FloatType) countdown;
        }
    }

    /** Compute the next value. */
    FloatType getNextValue() noexcept
    {
        if (countdown <= 0)
            return target;

        --countdown;
        currentValue += step;
        return currentValue;
    }

    /** Returns true if the current value is currently being interpolated. */
    bool isSmoothing() const noexcept
    {
        return countdown > 0;
    }

    /** Returns the target value towards which the smoothed value is currently moving. */
    FloatType getTargetValue() const noexcept
    {
        return target;
    }

private:
    //==============================================================================
    FloatType currentValue, target, step;
    int countdown, stepsToTarget;
};