1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
|
/*
* Copyright (C) 2015 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 com.android.bluetoothmidiservice;
import android.media.midi.MidiReceiver;
import com.android.internal.midi.MidiConstants;
import com.android.internal.midi.MidiFramer;
import java.io.IOException;
/**
* This class accumulates MIDI messages to form a MIDI packet.
*/
public class BluetoothPacketEncoder extends PacketEncoder {
private static final String TAG = "BluetoothPacketEncoder";
private static final long MILLISECOND_NANOS = 1000000L;
// mask for generating 13 bit timestamps
private static final int MILLISECOND_MASK = 0x1FFF;
private final PacketReceiver mPacketReceiver;
// buffer for accumulating messages to write
private final byte[] mAccumulationBuffer;
// number of bytes currently in mAccumulationBuffer
private int mAccumulatedBytes;
// timestamp for first message in current packet
private int mPacketTimestamp;
// current running status, or zero if none
private int mRunningStatus;
private boolean mWritePending;
private final Object mLock = new Object();
// This receives normalized data from mMidiFramer and accumulates it into a packet buffer
private final MidiReceiver mFramedDataReceiver = new MidiReceiver() {
@Override
public void onReceive(byte[] msg, int offset, int count, long timestamp)
throws IOException {
int milliTimestamp = (int)(timestamp / MILLISECOND_NANOS) & MILLISECOND_MASK;
int status = msg[0] & 0xFF;
synchronized (mLock) {
boolean needsTimestamp = (milliTimestamp != mPacketTimestamp);
int bytesNeeded = count;
if (needsTimestamp) bytesNeeded++; // add one for timestamp byte
if (status == mRunningStatus) bytesNeeded--; // subtract one for status byte
if (mAccumulatedBytes + bytesNeeded > mAccumulationBuffer.length) {
// write out our data if there is no more room
// if necessary, block until previous packet is sent
flushLocked(true);
}
// write header if we are starting a new packet
if (mAccumulatedBytes == 0) {
// header byte with timestamp bits 7 - 12
mAccumulationBuffer[mAccumulatedBytes++] = (byte)(0x80 | (milliTimestamp >> 7));
mPacketTimestamp = milliTimestamp;
needsTimestamp = true;
}
// write new timestamp byte and status byte if necessary
if (needsTimestamp) {
// timestamp byte with bits 0 - 6 of timestamp
mAccumulationBuffer[mAccumulatedBytes++] =
(byte)(0x80 | (milliTimestamp & 0x7F));
mPacketTimestamp = milliTimestamp;
}
if (status != mRunningStatus) {
mAccumulationBuffer[mAccumulatedBytes++] = (byte)status;
if (MidiConstants.allowRunningStatus(status)) {
mRunningStatus = status;
} else if (MidiConstants.allowRunningStatus(status)) {
mRunningStatus = 0;
}
}
// now copy data bytes
int dataLength = count - 1;
System.arraycopy(msg, 1, mAccumulationBuffer, mAccumulatedBytes, dataLength);
// FIXME - handle long SysEx properly
mAccumulatedBytes += dataLength;
// write the packet if possible, but do not block
flushLocked(false);
}
}
};
// MidiFramer for normalizing incoming data
private final MidiFramer mMidiFramer = new MidiFramer(mFramedDataReceiver);
public BluetoothPacketEncoder(PacketReceiver packetReceiver, int maxPacketSize) {
mPacketReceiver = packetReceiver;
mAccumulationBuffer = new byte[maxPacketSize];
}
@Override
public void onReceive(byte[] msg, int offset, int count, long timestamp)
throws IOException {
// normalize the data by passing it through a MidiFramer first
mMidiFramer.sendWithTimestamp(msg, offset, count, timestamp);
}
@Override
public void writeComplete() {
synchronized (mLock) {
mWritePending = false;
flushLocked(false);
mLock.notify();
}
}
private void flushLocked(boolean canBlock) {
if (mWritePending && !canBlock) {
return;
}
while (mWritePending && mAccumulatedBytes > 0) {
try {
mLock.wait();
} catch (InterruptedException e) {
// try again
continue;
}
}
if (mAccumulatedBytes > 0) {
mPacketReceiver.writePacket(mAccumulationBuffer, mAccumulatedBytes);
mAccumulatedBytes = 0;
mPacketTimestamp = 0;
mRunningStatus = 0;
mWritePending = true;
}
}
}
|
