Patrick Thomas / MIDIparser

A class that converts byte streams into MIDI messages, and stores them in a FIFO. This is useful if you wish to read MIDI messages via polling instead of interrupts. The class supports every type of MIDI message, and System Realtime messages can be interleaved with regular ones.

MIDIparser.cpp

Committer:
Padman
Date:
2016-08-04
Revision:
2:cbd43ba7f842
Parent:
1:1c3f0c6ea0fb

File content as of revision 2:cbd43ba7f842:

/**
 * @file    MIDIparser.cpp
 * @brief   MIDI parser - converts bytes into queued MIDI messages
 * @author  Patrick Thomas
 * @version 1.0
 * @see     
 *
 * Copyright (c) 2016
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "MIDIparser.h"

MIDIparser::MIDIparser() {

}

void MIDIparser::parse(uint8_t this_byte) {

    // Data byte
    if (this_byte < 128) {

        // We expect the output buffer to be non-empty here
        if (input_vector.available()) {

            input_vector.put(this_byte);

            // Dual condition - perform one more read after this
            if (!sysex && dual) dual = false;

            // Single condition - send two bytes now
            else if (!sysex && !dual) {

                output_queue.push(MIDIMessage(input_vector.head(), input_vector.size()));
                input_vector.clear();
            }
        }
    }

    // System realtime byte
    else if (this_byte > 243) {

        switch (this_byte & 0xF) {

        // Undefined
        case 4:
        case 5:
            break;

            // Sysex end
        case 7:
            // Only output valid Sysex data
            if (sysex && !dual) output_queue.push(MIDIMessage(input_vector.head(), input_vector.size()));
            input_vector.clear();
            break;

            // Realtime
        default:
            output_queue.push(MIDIMessage(&this_byte, 1));
            break;
        }
    }

    // Status byte
    else {

        // We expect the output buffer to be empty here
        if (!input_vector.available()) {

            input_vector.put(this_byte);

            // Set flags
            switch ((this_byte >> 4) & 7) {
            case 0:
            case 1:
            case 2:
            case 3:
            case 6:
                sysex = false;
                dual = true;
                break;

            case 4:
            case 5:
                sysex = false;
                dual = false;
                break;

            case 7:
                switch (this_byte & 7) {
                case 0:
                    sysex = true;
                    dual = false;
                    break;

                case 1:
                case 3:
                    sysex = false;
                    dual = false;
                    break;

                case 2:
                    sysex = false;
                    dual = true;
                    break;

                default:
                    break;
                }
                break;

                default:
                    break;
            }
        }

        // Invalidate the output buffer by setting flags
        else {
            sysex = true;
            dual = true;
        }
    }
}

uint32_t MIDIparser::available() { return !output_queue.empty(); }

MIDIMessage MIDIparser::grab() {

    MIDIMessage output;
    output = output_queue.front();
    output_queue.pop();
    return output;
}