MidiReceiver.java revision b6f50d357bd3d4d296be6bb047f5ce93a79cbca1 
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     * Called to pass MIDI data to the receiver.
27     * May fail if count exceeds {@link #getMaxMessageSize}.
28     *
29     * NOTE: the msg array parameter is only valid within the context of this call.
30     * The msg bytes should be copied by the receiver rather than retaining a reference
31     * to this parameter.
32     * Also, modifying the contents of the msg array parameter may result in other receivers
33     * in the same application receiving incorrect values in their {link #onReceive} method.
34     *
35     * @param msg a byte array containing the MIDI data
36     * @param offset the offset of the first byte of the data in the array to be processed
37     * @param count the number of bytes of MIDI data in the array to be processed
38     * @param timestamp the timestamp of the message (based on {@link java.lang.System#nanoTime}
39     * @throws IOException
40     */
41    abstract public void onReceive(byte[] msg, int offset, int count, long timestamp)
42            throws IOException;
43
44    /**
45     * Instructs the receiver to discard all pending events.
46     * @throws IOException
47     */
48    public void flush() throws IOException {
49    }
50
51    /**
52     * Returns the maximum size of a message this receiver can receive.
53     * Defaults to {@link java.lang.Integer#MAX_VALUE} unless overridden.
54     * @return maximum message size
55     */
56    public int getMaxMessageSize() {
57        return Integer.MAX_VALUE;
58    }
59
60    /**
61     * Called to send MIDI data to the receiver
62     * Data will get split into multiple calls to {@link #onReceive} if count exceeds
63     * {@link #getMaxMessageSize}.
64     *
65     * @param msg a byte array containing the MIDI data
66     * @param offset the offset of the first byte of the data in the array to be sent
67     * @param count the number of bytes of MIDI data in the array to be sent
68     * @throws IOException
69     */
70    public void send(byte[] msg, int offset, int count) throws IOException {
71        sendWithTimestamp(msg, offset, count, System.nanoTime());
72    }
73
74    /**
75     * Called to send MIDI data to the receiver to be handled at a specified time in the future
76     * Data will get split into multiple calls to {@link #onReceive} if count exceeds
77     * {@link #getMaxMessageSize}.
78     *
79     * @param msg a byte array containing the MIDI data
80     * @param offset the offset of the first byte of the data in the array to be sent
81     * @param count the number of bytes of MIDI data in the array to be sent
82     * @param timestamp the timestamp of the message (based on {@link java.lang.System#nanoTime}
83     * @throws IOException
84     */
85    public void sendWithTimestamp(byte[] msg, int offset, int count, long timestamp)
86            throws IOException {
87        int messageSize = getMaxMessageSize();
88        while (count > 0) {
89            int length = (count > messageSize ? messageSize : count);
90            onReceive(msg, offset, length, timestamp);
91            offset += length;
92            count -= length;
93        }
94    }
95}
96