JUCE/modules/juce_audio_devices/midi_io/juce_MidiMessageCollector.h

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

   This file is part of the JUCE library.
   Copyright (c) 2020 - 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
{

//==============================================================================
/**
    Collects incoming realtime MIDI messages and turns them into blocks suitable for
    processing by a block-based audio callback.

    The class can also be used as either a MidiKeyboardState::Listener or a MidiInputCallback
    so it can easily use a midi input or keyboard component as its source.

    @see MidiMessage, MidiInput

    @tags{Audio}
*/
class JUCE_API  MidiMessageCollector    : public MidiKeyboardState::Listener,
                                          public MidiInputCallback
{
public:
    //==============================================================================
    /** Creates a MidiMessageCollector. */
    MidiMessageCollector();

    /** Destructor. */
    ~MidiMessageCollector() override;

    //==============================================================================
    /** Clears any messages from the queue.

        You need to call this method before starting to use the collector, so that
        it knows the correct sample rate to use.
    */
    void reset (double sampleRate);

    /** Takes an incoming real-time message and adds it to the queue.

        The message's timestamp is taken, and it will be ready for retrieval as part
        of the block returned by the next call to removeNextBlockOfMessages().

        This method is fully thread-safe when overlapping calls are made with
        removeNextBlockOfMessages().
    */
    void addMessageToQueue (const MidiMessage& message);

    /** Removes all the pending messages from the queue as a buffer.

        This will also correct the messages' timestamps to make sure they're in
        the range 0 to numSamples - 1.

        This call should be made regularly by something like an audio processing
        callback, because the time that it happens is used in calculating the
        midi event positions.

        This method is fully thread-safe when overlapping calls are made with
        addMessageToQueue().

        Precondition: numSamples must be greater than 0.
    */
    void removeNextBlockOfMessages (MidiBuffer& destBuffer, int numSamples);

    /** Preallocates storage for collected messages.

        This can be called before audio processing begins to ensure that there
        is sufficient space for the expected MIDI messages, in order to avoid
        allocations within the audio callback.
    */
    void ensureStorageAllocated (size_t bytes);


    //==============================================================================
    /** @internal */
    void handleNoteOn (MidiKeyboardState*, int midiChannel, int midiNoteNumber, float velocity) override;
    /** @internal */
    void handleNoteOff (MidiKeyboardState*, int midiChannel, int midiNoteNumber, float velocity) override;
    /** @internal */
    void handleIncomingMidiMessage (MidiInput*, const MidiMessage&) override;

private:
    //==============================================================================
    double lastCallbackTime = 0;
    CriticalSection midiCallbackLock;
    MidiBuffer incomingMessages;
    double sampleRate = 44100.0;
   #if JUCE_DEBUG
    bool hasCalledReset = false;
   #endif

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (MidiMessageCollector)
};

} // namespace juce