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 
17 package android.media.midi;
18 
19 import java.io.IOException;
20 
21 /**
22  * Interface for sending and receiving data to and from a MIDI device.
23  */
24 abstract public class MidiReceiver {
25 
26     private final int mMaxMessageSize;
27 
28     /**
29      * Default MidiReceiver constructor. Maximum message size is set to
30      * {@link java.lang.Integer#MAX_VALUE}
31      */
MidiReceiver()32     public MidiReceiver() {
33         mMaxMessageSize = Integer.MAX_VALUE;
34     }
35 
36     /**
37      * MidiReceiver constructor.
38      * @param maxMessageSize the maximum size of a message this receiver can receive
39      */
MidiReceiver(int maxMessageSize)40     public MidiReceiver(int maxMessageSize) {
41         mMaxMessageSize = maxMessageSize;
42     }
43 
44     /**
45      * Called whenever the receiver is passed new MIDI data.
46      * Subclasses override this method to receive MIDI data.
47      * May fail if count exceeds {@link #getMaxMessageSize}.
48      *
49      * NOTE: the msg array parameter is only valid within the context of this call.
50      * The msg bytes should be copied by the receiver rather than retaining a reference
51      * to this parameter.
52      * Also, modifying the contents of the msg array parameter may result in other receivers
53      * in the same application receiving incorrect values in their {link #onSend} method.
54      *
55      * @param msg a byte array containing the MIDI data
56      * @param offset the offset of the first byte of the data in the array to be processed
57      * @param count the number of bytes of MIDI data in the array to be processed
58      * @param timestamp the timestamp of the message (based on {@link java.lang.System#nanoTime}
59      * @throws IOException
60      */
onSend(byte[] msg, int offset, int count, long timestamp)61     abstract public void onSend(byte[] msg, int offset, int count, long timestamp)
62             throws IOException;
63 
64     /**
65      * Instructs the receiver to discard all pending MIDI data.
66      * @throws IOException
67      */
flush()68     public void flush() throws IOException {
69         onFlush();
70     }
71 
72     /**
73      * Called when the receiver is instructed to discard all pending MIDI data.
74      * Subclasses should override this method if they maintain a list or queue of MIDI data
75      * to be processed in the future.
76      * @throws IOException
77      */
onFlush()78     public void onFlush() throws IOException {
79     }
80 
81     /**
82      * Returns the maximum size of a message this receiver can receive.
83      * @return maximum message size
84      */
getMaxMessageSize()85     public final int getMaxMessageSize() {
86         return mMaxMessageSize;
87     }
88 
89     /**
90      * Called to send MIDI data to the receiver without a timestamp.
91      * Data will be processed by receiver in the order sent.
92      * Data will get split into multiple calls to {@link #onSend} if count exceeds
93      * {@link #getMaxMessageSize}.  Blocks until all the data is sent or an exception occurs.
94      * In the latter case, the amount of data sent prior to the exception is not provided to caller.
95      * The communication should be considered corrupt.  The sender should reestablish
96      * communication, reset all controllers and send all notes off.
97      *
98      * @param msg a byte array containing the MIDI data
99      * @param offset the offset of the first byte of the data in the array to be sent
100      * @param count the number of bytes of MIDI data in the array to be sent
101      * @throws IOException if the data could not be sent in entirety
102      */
send(byte[] msg, int offset, int count)103     public void send(byte[] msg, int offset, int count) throws IOException {
104         // TODO add public static final TIMESTAMP_NONE = 0L
105         send(msg, offset, count, 0L);
106     }
107 
108     /**
109      * Called to send MIDI data to the receiver with a specified timestamp.
110      * Data will be processed by receiver in order first by timestamp, then in the order sent.
111      * Data will get split into multiple calls to {@link #onSend} if count exceeds
112      * {@link #getMaxMessageSize}.  Blocks until all the data is sent or an exception occurs.
113      * In the latter case, the amount of data sent prior to the exception is not provided to caller.
114      * The communication should be considered corrupt.  The sender should reestablish
115      * communication, reset all controllers and send all notes off.
116      *
117      * @param msg a byte array containing the MIDI data
118      * @param offset the offset of the first byte of the data in the array to be sent
119      * @param count the number of bytes of MIDI data in the array to be sent
120      * @param timestamp the timestamp of the message, based on {@link java.lang.System#nanoTime}
121      * @throws IOException if the data could not be sent in entirety
122      */
send(byte[] msg, int offset, int count, long timestamp)123     public void send(byte[] msg, int offset, int count, long timestamp)
124             throws IOException {
125         int messageSize = getMaxMessageSize();
126         while (count > 0) {
127             int length = (count > messageSize ? messageSize : count);
128             onSend(msg, offset, length, timestamp);
129             offset += length;
130             count -= length;
131         }
132     }
133 }
134