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/*
* 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.util.Log;
import java.io.Closeable;
/**
* This class represents a MIDI input or output port.
* Base class for {@link MidiInputPort} and {@link MidiOutputPort}
*
* CANDIDATE FOR PUBLIC API
* @hide
*/
abstract public class MidiPort implements Closeable {
private static final String TAG = "MidiPort";
private final int mPortNumber;
/**
* Maximum size of a packet that can pass through our ParcelFileDescriptor.
* For internal use only. Implementation details may change in the future.
* @hide
*/
public static final int MAX_PACKET_SIZE = 1024;
/**
* size of message timestamp in bytes
* For internal use only. Implementation details may change in the future.
* @hide
*/
private static final int TIMESTAMP_SIZE = 8;
/**
* Maximum amount of MIDI data that can be included in a packet
*/
public static final int MAX_PACKET_DATA_SIZE = MAX_PACKET_SIZE - TIMESTAMP_SIZE;
/* package */ MidiPort(int portNumber) {
mPortNumber = portNumber;
}
/**
* Returns the port number of this port
*
* @return the port's port number
*/
public final int getPortNumber() {
return mPortNumber;
}
/**
* Called when an IOExeption occurs while sending or receiving data.
* Subclasses can override to be notified of such errors
*
* @hide
*/
public void onIOException() {
}
/**
* Utility function for packing a MIDI message to be sent through our ParcelFileDescriptor
*
* message byte array contains variable length MIDI message.
* messageSize is size of variable length MIDI message
* timestamp is message timestamp to pack
* dest is buffer to pack into
* returns size of packed message
*
* For internal use only. Implementation details may change in the future.
* @hide
*/
public static int packMessage(byte[] message, int offset, int size, long timestamp,
byte[] dest) {
if (size + TIMESTAMP_SIZE > MAX_PACKET_SIZE) {
size = MAX_PACKET_SIZE - TIMESTAMP_SIZE;
}
// message data goes first
System.arraycopy(message, offset, dest, 0, size);
// followed by timestamp
for (int i = 0; i < TIMESTAMP_SIZE; i++) {
dest[size++] = (byte)timestamp;
timestamp >>= 8;
}
return size;
}
/**
* Utility function for unpacking a MIDI message received from our ParcelFileDescriptor
* returns the offset of the MIDI message in packed buffer
*
* For internal use only. Implementation details may change in the future.
* @hide
*/
public static int getMessageOffset(byte[] buffer, int bufferLength) {
// message is at the beginning
return 0;
}
/**
* Utility function for unpacking a MIDI message received from our ParcelFileDescriptor
* returns size of MIDI data in packed buffer
*
* For internal use only. Implementation details may change in the future.
* @hide
*/
public static int getMessageSize(byte[] buffer, int bufferLength) {
// message length is total buffer length minus size of the timestamp
return bufferLength - TIMESTAMP_SIZE;
}
/**
* Utility function for unpacking a MIDI message received from our ParcelFileDescriptor
* unpacks timestamp from packed buffer
*
* For internal use only. Implementation details may change in the future.
* @hide
*/
public static long getMessageTimeStamp(byte[] buffer, int bufferLength) {
// timestamp is at end of the packet
int offset = bufferLength;
long timestamp = 0;
for (int i = 0; i < TIMESTAMP_SIZE; i++) {
int b = (int)buffer[--offset] & 0xFF;
timestamp = (timestamp << 8) | b;
}
return timestamp;
}
}
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