MidiReceiver.java revision d8f6363a5d9c72f1ed22f79bc16563123dff4803 
1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.media.midi;
18
19import java.io.IOException;
20
21/**
22 * Interface for sending and receiving data to and from a MIDI device.
23 */
24abstract public class MidiReceiver {
25    /**
26     * Although public, this method should be considered a private implementation
27     * detail. Client code should call {@link #send} or {@link #sendWithTimestamp}
28     * instead.
29     *
30     * Called to pass MIDI data to the receiver.
31     * May fail if count exceeds {@link #getMaxMessageSize}.
32     *
33     * NOTE: the msg array parameter is only valid within the context of this call.
34     * The msg bytes should be copied by the receiver rather than retaining a reference
35     * to this parameter.
36     * Also, modifying the contents of the msg array parameter may result in other receivers
37     * in the same application receiving incorrect values in their {link #onReceive} method.
38     *
39     * @param msg a byte array containing the MIDI data
40     * @param offset the offset of the first byte of the data in the array to be processed
41     * @param count the number of bytes of MIDI data in the array to be processed
42     * @param timestamp the timestamp of the message (based on {@link java.lang.System#nanoTime}
43     * @throws IOException
44     */
45    abstract public void onReceive(byte[] msg, int offset, int count, long timestamp)
46            throws IOException;
47
48    /**
49     * Instructs the receiver to discard all pending events.
50     * @throws IOException
51     */
52    public void flush() throws IOException {
53    }
54
55    /**
56     * Returns the maximum size of a message this receiver can receive.
57     * Defaults to {@link java.lang.Integer#MAX_VALUE} unless overridden.
58     * @return maximum message size
59     */
60    public int getMaxMessageSize() {
61        return Integer.MAX_VALUE;
62    }
63
64    /**
65     * Called to send MIDI data to the receiver
66     * Data will get split into multiple calls to {@link #onReceive} if count exceeds
67     * {@link #getMaxMessageSize}.
68     *
69     * @param msg a byte array containing the MIDI data
70     * @param offset the offset of the first byte of the data in the array to be sent
71     * @param count the number of bytes of MIDI data in the array to be sent
72     * @throws IOException
73     */
74    public void send(byte[] msg, int offset, int count) throws IOException {
75        sendWithTimestamp(msg, offset, count, System.nanoTime());
76    }
77
78    /**
79     * Called to send MIDI data to the receiver to be handled at a specified time in the future
80     * Data will get split into multiple calls to {@link #onReceive} if count exceeds
81     * {@link #getMaxMessageSize}.
82     *
83     * @param msg a byte array containing the MIDI data
84     * @param offset the offset of the first byte of the data in the array to be sent
85     * @param count the number of bytes of MIDI data in the array to be sent
86     * @param timestamp the timestamp of the message (based on {@link java.lang.System#nanoTime}
87     * @throws IOException
88     */
89    public void sendWithTimestamp(byte[] msg, int offset, int count, long timestamp)
90            throws IOException {
91        int messageSize = getMaxMessageSize();
92        while (count > 0) {
93            int length = (count > messageSize ? messageSize : count);
94            onReceive(msg, offset, length, timestamp);
95            offset += length;
96            count -= length;
97        }
98    }
99}
100