| /* |
| * 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; |
| |
| /** |
| * This class contains utilities for socket communication between a |
| * MidiInputPort and MidiOutputPort |
| */ |
| /* package */ class MidiPortImpl { |
| private static final String TAG = "MidiPort"; |
| |
| /** |
| * Packet type for data packet |
| */ |
| public static final int PACKET_TYPE_DATA = 1; |
| |
| /** |
| * Packet type for flush packet |
| */ |
| public static final int PACKET_TYPE_FLUSH = 2; |
| |
| /** |
| * Maximum size of a packet that can be passed between processes. |
| */ |
| public static final int MAX_PACKET_SIZE = 1024; |
| |
| /** |
| * size of message timestamp in bytes |
| */ |
| private static final int TIMESTAMP_SIZE = 8; |
| |
| /** |
| * Data packet overhead is timestamp size plus packet type byte |
| */ |
| private static final int DATA_PACKET_OVERHEAD = TIMESTAMP_SIZE + 1; |
| |
| /** |
| * Maximum amount of MIDI data that can be included in a packet |
| */ |
| public static final int MAX_PACKET_DATA_SIZE = MAX_PACKET_SIZE - DATA_PACKET_OVERHEAD; |
| |
| /** |
| * Utility function for packing MIDI data to be passed between processes |
| * |
| * 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 |
| */ |
| public static int packData(byte[] message, int offset, int size, long timestamp, |
| byte[] dest) { |
| if (size > MAX_PACKET_DATA_SIZE) { |
| size = MAX_PACKET_DATA_SIZE; |
| } |
| int length = 0; |
| // packet type goes first |
| dest[length++] = PACKET_TYPE_DATA; |
| // data goes next |
| System.arraycopy(message, offset, dest, length, size); |
| length += size; |
| |
| // followed by timestamp |
| for (int i = 0; i < TIMESTAMP_SIZE; i++) { |
| dest[length++] = (byte)timestamp; |
| timestamp >>= 8; |
| } |
| |
| return length; |
| } |
| |
| /** |
| * Utility function for packing a flush command to be passed between processes |
| */ |
| public static int packFlush(byte[] dest) { |
| dest[0] = PACKET_TYPE_FLUSH; |
| return 1; |
| } |
| |
| /** |
| * Returns the packet type (PACKET_TYPE_DATA or PACKET_TYPE_FLUSH) |
| */ |
| public static int getPacketType(byte[] buffer, int bufferLength) { |
| return buffer[0]; |
| } |
| |
| /** |
| * Utility function for unpacking MIDI data received from other process |
| * returns the offset of the MIDI message in packed buffer |
| */ |
| public static int getDataOffset(byte[] buffer, int bufferLength) { |
| // data follows packet type byte |
| return 1; |
| } |
| |
| /** |
| * Utility function for unpacking MIDI data received from other process |
| * returns size of MIDI data in packed buffer |
| */ |
| public static int getDataSize(byte[] buffer, int bufferLength) { |
| // message length is total buffer length minus size of the timestamp |
| return bufferLength - DATA_PACKET_OVERHEAD; |
| } |
| |
| /** |
| * Utility function for unpacking MIDI data received from other process |
| * unpacks timestamp from packed buffer |
| */ |
| public static long getPacketTimestamp(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; |
| } |
| } |