de.ailis.midi4js.MessageReceiver.java Source code

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Here is the source code for de.ailis.midi4js.MessageReceiver.java

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/*
 * Copyright (C) 2012 Klaus Reimer <k@ailis.de>
 * See LICENSE.txt for licensing information.
 */

package de.ailis.midi4js;

import javax.sound.midi.MetaMessage;
import javax.sound.midi.MidiMessage;
import javax.sound.midi.Receiver;
import javax.sound.midi.ShortMessage;
import javax.sound.midi.SysexMessage;

import org.json.JSONException;
import org.json.JSONStringer;

/**
 * Message receiver which encapsulates the received message into a JSON
 * object and then sends it to the JavaScript part of Midi4JS.
 *
 * @author Klaus Reimer (k@ailis.de)
 */
public final class MessageReceiver implements Receiver {
    /** The Midi4JS applet. */
    private final Midi4JS applet;

    /**
     * Constructor.
     *
     * @param applet
     *            The Midi4JS applet.
     */
    MessageReceiver(final Midi4JS applet) {
        this.applet = applet;
    }

    /**
     * @see javax.sound.midi.Receiver#send(javax.sound.midi.MidiMessage, long)
     */
    @Override
    public void send(final MidiMessage message, final long timeStamp) {
        try {
            final JSONStringer json = new JSONStringer();
            json.object();
            json.key("status").value(message.getStatus());
            json.key("message");
            json.array();
            final byte[] data = message.getMessage();
            final int max = Math.min(data.length, message.getLength());
            for (int i = 0; i < max; i++)
                json.value(data[i] & 0xff);
            json.endArray();
            if (message instanceof ShortMessage)
                processShortMessage((ShortMessage) message, json);
            else if (message instanceof MetaMessage)
                processMetaMessage((MetaMessage) message, json);
            else if (message instanceof SysexMessage)
                processSysexMessage((SysexMessage) message, json);
            json.endObject();
            this.applet.execJSMethod("messageReceived", System.identityHashCode(this), json.toString(), timeStamp);
        } catch (final JSONException e) {
            throw new RuntimeException(e.toString(), e);
        }
    }

    /**
     * Processes a short message.
     *
     * @param message
     *            The message to process.
     * @param json
     *            The JSON stringer.
     * @throws JSONException
     *             When JSON output fails.
     */
    private void processShortMessage(final ShortMessage message, final JSONStringer json) throws JSONException {
        json.key("class").value("ShortMessage");
        json.key("channel").value(message.getChannel());
        json.key("command").value(message.getCommand());
        json.key("data1").value(message.getData1());
        json.key("data2").value(message.getData2());
    }

    /**
     * Processes a meta message.
     *
     * @param message
     *            The message to process.
     * @param json
     *            The JSON stringer.
     * @throws JSONException
     *             When JSON output fails.
     */
    private void processMetaMessage(final MetaMessage message, final JSONStringer json) throws JSONException {
        json.key("class").value("MetaMessage");
        json.key("type").value(message.getType());
        json.key("data");
        json.array();
        final byte[] data = message.getMessage();
        final int max = Math.min(data.length, message.getLength());
        for (int i = 0; i < max; i++)
            json.value(data[i] & 0xff);
        json.endArray();
    }

    /**
     * Processes a sysex message.
     *
     * @param message
     *            The message to process.
     * @param json
     *            The JSON stringer.
     * @throws JSONException
     *             When JSON output fails.
     */
    private void processSysexMessage(final SysexMessage message, final JSONStringer json) throws JSONException {
        json.key("class").value("SysexMessage");
        json.key("data");
        json.array();
        final byte[] data = message.getMessage();
        final int max = Math.min(data.length, message.getLength());
        for (int i = 0; i < max; i++)
            json.value(data[i] & 0xff);
        json.endArray();
    }

    /**
     * @see javax.sound.midi.Receiver#close()
     */
    @Override
    public void close() {
        // Nothing to do here.
    }
}