https://source.android.com/ 
/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * 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.
 */

package android.media.midi;

import android.os.Binder;
import android.os.IBinder;
import android.os.Process;
import android.os.RemoteException;
import android.util.Log;

import dalvik.system.CloseGuard;

import libcore.io.IoUtils;

import java.io.Closeable;
import java.io.FileDescriptor;
import java.io.IOException;

import java.util.HashSet;


This class is used for sending and receiving data to and from a MIDI device Instances of this class are created by MidiManager.openDevice. 
/**
 * This class is used for sending and receiving data to and from a MIDI device
 * Instances of this class are created by {@link MidiManager#openDevice}.
 */
public final class MidiDevice implements Closeable {
    static {
        System.loadLibrary("media_jni");
    }

    private static final String TAG = "MidiDevice";

    private final MidiDeviceInfo mDeviceInfo;
    private final IMidiDeviceServer mDeviceServer;
    private final IMidiManager mMidiManager;
    private final IBinder mClientToken;
    private final IBinder mDeviceToken;
    private boolean mIsDeviceClosed;

    // Native API Helpers
    
Keep a static list of MidiDevice objects that are mirrorToNative()'d so they
don't get inadvertantly garbage collected.

/**
     * Keep a static list of MidiDevice objects that are mirrorToNative()'d so they
     * don't get inadvertantly garbage collected.
     */
    private static HashSet<MidiDevice> mMirroredDevices = new HashSet<MidiDevice>();

    
If this device is mirrorToNatived(), this is the native device handler.

/**
     * If this device is mirrorToNatived(), this is the native device handler.
     */
    private long mNativeHandle;

    private final CloseGuard mGuard = CloseGuard.get();

    
This class represents a connection between the output port of one device and the input port of another. Created by connectPorts. Close this object to terminate the connection. 
/**
     * This class represents a connection between the output port of one device
     * and the input port of another. Created by {@link #connectPorts}.
     * Close this object to terminate the connection.
     */
    public class MidiConnection implements Closeable {
        private final IMidiDeviceServer mInputPortDeviceServer;
        private final IBinder mInputPortToken;
        private final IBinder mOutputPortToken;
        private final CloseGuard mGuard = CloseGuard.get();
        private boolean mIsClosed;

        MidiConnection(IBinder outputPortToken, MidiInputPort inputPort) {
            mInputPortDeviceServer = inputPort.getDeviceServer();
            mInputPortToken = inputPort.getToken();
            mOutputPortToken = outputPortToken;
            mGuard.open("close");
        }

        @Override
        public void close() throws IOException {
            synchronized (mGuard) {
                if (mIsClosed) return;
                mGuard.close();
                try {
                    // close input port
                    mInputPortDeviceServer.closePort(mInputPortToken);
                    // close output port
                    mDeviceServer.closePort(mOutputPortToken);
                } catch (RemoteException e) {
                    Log.e(TAG, "RemoteException in MidiConnection.close");
                }
                mIsClosed = true;
            }
        }

        @Override
        protected void finalize() throws Throwable {
            try {
                if (mGuard != null) {
                    mGuard.warnIfOpen();
                }

                close();
            } finally {
                super.finalize();
            }
        }
    }

    /* package */ MidiDevice(MidiDeviceInfo deviceInfo, IMidiDeviceServer server,
            IMidiManager midiManager, IBinder clientToken, IBinder deviceToken) {
        mDeviceInfo = deviceInfo;
        mDeviceServer = server;
        mMidiManager = midiManager;
        mClientToken = clientToken;
        mDeviceToken = deviceToken;
        mGuard.open("close");
    }

    
Returns a MidiDeviceInfo object, which describes this device. 
Returns:the MidiDeviceInfo object
/**
     * Returns a {@link MidiDeviceInfo} object, which describes this device.
     *
     * @return the {@link MidiDeviceInfo} object
     */
    public MidiDeviceInfo getInfo() {
        return mDeviceInfo;
    }

    
Called to open a MidiInputPort for the specified port number. An input port can only be used by one sender at a time. Opening an input port will fail if another application has already opened it for use. A MidiDeviceStatus can be used to determine if an input port is already open. 
Params:
  • portNumber – the number of the input port to open
Returns:the MidiInputPort if the open is successful, or null in case of failure.
/**
     * Called to open a {@link MidiInputPort} for the specified port number.
     *
     * An input port can only be used by one sender at a time.
     * Opening an input port will fail if another application has already opened it for use.
     * A {@link MidiDeviceStatus} can be used to determine if an input port is already open.
     *
     * @param portNumber the number of the input port to open
     * @return the {@link MidiInputPort} if the open is successful,
     *         or null in case of failure.
     */
    public MidiInputPort openInputPort(int portNumber) {
        if (mIsDeviceClosed) {
            return null;
        }
        try {
            IBinder token = new Binder();
            FileDescriptor fd = mDeviceServer.openInputPort(token, portNumber);
            if (fd == null) {
                return null;
            }
            return new MidiInputPort(mDeviceServer, token, fd, portNumber);
        } catch (RemoteException e) {
            Log.e(TAG, "RemoteException in openInputPort");
            return null;
        }
    }

    
Called to open a MidiOutputPort for the specified port number. An output port may be opened by multiple applications. 
Params:
  • portNumber – the number of the output port to open
Returns:the MidiOutputPort if the open is successful, or null in case of failure.
/**
     * Called to open a {@link MidiOutputPort} for the specified port number.
     *
     * An output port may be opened by multiple applications.
     *
     * @param portNumber the number of the output port to open
     * @return the {@link MidiOutputPort} if the open is successful,
     *         or null in case of failure.
     */
    public MidiOutputPort openOutputPort(int portNumber) {
        if (mIsDeviceClosed) {
            return null;
        }
        try {
            IBinder token = new Binder();
            FileDescriptor fd = mDeviceServer.openOutputPort(token, portNumber);
            if (fd == null) {
                return null;
            }
            return new MidiOutputPort(mDeviceServer, token, fd, portNumber);
        } catch (RemoteException e) {
            Log.e(TAG, "RemoteException in openOutputPort");
            return null;
        }
    }

    
Connects the supplied MidiInputPort to the output port of this device with the specified port number. Once the connection is made, the MidiInput port instance can no longer receive data via its MidiReceiver.onSend method. This method returns a MidiConnection object, which can be used to close the connection. 
Params:
  • inputPort – the inputPort to connect
  • outputPortNumber – the port number of the output port to connect inputPort to.
Returns:MidiConnection object if the connection is successful, or null in case of failure.
/**
     * Connects the supplied {@link MidiInputPort} to the output port of this device
     * with the specified port number. Once the connection is made, the MidiInput port instance
     * can no longer receive data via its {@link MidiReceiver#onSend} method.
     * This method returns a {@link MidiDevice.MidiConnection} object, which can be used
     * to close the connection.
     *
     * @param inputPort the inputPort to connect
     * @param outputPortNumber the port number of the output port to connect inputPort to.
     * @return {@link MidiDevice.MidiConnection} object if the connection is successful,
     *         or null in case of failure.
     */
    public MidiConnection connectPorts(MidiInputPort inputPort, int outputPortNumber) {
        if (outputPortNumber < 0 || outputPortNumber >= mDeviceInfo.getOutputPortCount()) {
            throw new IllegalArgumentException("outputPortNumber out of range");
        }
        if (mIsDeviceClosed) {
            return null;
        }

        FileDescriptor fd = inputPort.claimFileDescriptor();
        if (fd == null) {
            return null;
        }
        try {
            IBinder token = new Binder();
            int calleePid = mDeviceServer.connectPorts(token, fd, outputPortNumber);
            // If the service is a different Process then it will duplicate the fd
            // and we can safely close this one.
            // But if the service is in the same Process then closing the fd will
            // kill the connection. So don't do that.
            if (calleePid != Process.myPid()) {
                // close our copy of the file descriptor
                IoUtils.closeQuietly(fd);
            }

            return new MidiConnection(token, inputPort);
        } catch (RemoteException e) {
            Log.e(TAG, "RemoteException in connectPorts");
            return null;
        }
    }

    
Makes Midi Device available to the Native API

@hide
/**
     * Makes Midi Device available to the Native API
     * @hide
     */
    public long mirrorToNative() throws IOException {
        if (mIsDeviceClosed || mNativeHandle != 0) {
            return 0;
        }

        mNativeHandle = native_mirrorToNative(mDeviceServer.asBinder(), mDeviceInfo.getId());
        if (mNativeHandle == 0) {
            throw new IOException("Failed mirroring to native");
        }

        synchronized (mMirroredDevices) {
            mMirroredDevices.add(this);
        }
        return mNativeHandle;
    }

    
Makes Midi Device no longer available to the Native API

@hide
/**
     * Makes Midi Device no longer available to the Native API
     * @hide
     */
    public void removeFromNative() {
        if (mNativeHandle == 0) {
            return;
        }

        synchronized (mGuard) {
            native_removeFromNative(mNativeHandle);
            mNativeHandle = 0;
        }

        synchronized (mMirroredDevices) {
            mMirroredDevices.remove(this);
        }
    }

    @Override
    public void close() throws IOException {
        synchronized (mGuard) {
            if (!mIsDeviceClosed) {
                removeFromNative();
                mGuard.close();
                mIsDeviceClosed = true;
                try {
                    mMidiManager.closeDevice(mClientToken, mDeviceToken);
                } catch (RemoteException e) {
                    Log.e(TAG, "RemoteException in closeDevice");
                }
            }
        }
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            if (mGuard != null) {
                mGuard.warnIfOpen();
            }

            close();
        } finally {
            super.finalize();
        }
    }

    @Override
    public String toString() {
        return ("MidiDevice: " + mDeviceInfo.toString());
    }

    private native long native_mirrorToNative(IBinder deviceServerBinder, int id);
    private native void native_removeFromNative(long deviceHandle);
}