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      1 /*
      2  * Copyright (C) 2015 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 com.example.android.common.midi;
     18 
     19 import android.media.midi.MidiReceiver;
     20 import android.util.Log;
     21 
     22 import java.io.IOException;
     23 
     24 /**
     25  * Convert stream of arbitrary MIDI bytes into discrete messages.
     26  *
     27  * Parses the incoming bytes and then posts individual messages to the receiver
     28  * specified in the constructor. Short messages of 1-3 bytes will be complete.
     29  * System Exclusive messages may be posted in pieces.
     30  *
     31  * Resolves Running Status and interleaved System Real-Time messages.
     32  */
     33 public class MidiFramer extends MidiReceiver {
     34     private MidiReceiver mReceiver;
     35     private byte[] mBuffer = new byte[3];
     36     private int mCount;
     37     private byte mRunningStatus;
     38     private int mNeeded;
     39     private boolean mInSysEx;
     40 
     41     public MidiFramer(MidiReceiver receiver) {
     42         mReceiver = receiver;
     43     }
     44 
     45     /*
     46      * @see android.midi.MidiReceiver#onSend(byte[], int, int, long)
     47      */
     48     @Override
     49     public void onSend(byte[] data, int offset, int count, long timestamp)
     50             throws IOException {
     51         int sysExStartOffset = (mInSysEx ? offset : -1);
     52 
     53         for (int i = 0; i < count; i++) {
     54             final byte currentByte = data[offset];
     55             final int currentInt = currentByte & 0xFF;
     56             if (currentInt >= 0x80) { // status byte?
     57                 if (currentInt < 0xF0) { // channel message?
     58                     mRunningStatus = currentByte;
     59                     mCount = 1;
     60                     mNeeded = MidiConstants.getBytesPerMessage(currentByte) - 1;
     61                 } else if (currentInt < 0xF8) { // system common?
     62                     if (currentInt == 0xF0 /* SysEx Start */) {
     63                         // Log.i(TAG, "SysEx Start");
     64                         mInSysEx = true;
     65                         sysExStartOffset = offset;
     66                     } else if (currentInt == 0xF7 /* SysEx End */) {
     67                         // Log.i(TAG, "SysEx End");
     68                         if (mInSysEx) {
     69                             mReceiver.send(data, sysExStartOffset,
     70                                 offset - sysExStartOffset + 1, timestamp);
     71                             mInSysEx = false;
     72                             sysExStartOffset = -1;
     73                         }
     74                     } else {
     75                         mBuffer[0] = currentByte;
     76                         mRunningStatus = 0;
     77                         mCount = 1;
     78                         mNeeded = MidiConstants.getBytesPerMessage(currentByte) - 1;
     79                     }
     80                 } else { // real-time?
     81                     // Single byte message interleaved with other data.
     82                     if (mInSysEx) {
     83                         mReceiver.send(data, sysExStartOffset,
     84                                 offset - sysExStartOffset, timestamp);
     85                         sysExStartOffset = offset + 1;
     86                     }
     87                     mReceiver.send(data, offset, 1, timestamp);
     88                 }
     89             } else { // data byte
     90                 if (!mInSysEx) {
     91                     mBuffer[mCount++] = currentByte;
     92                     if (--mNeeded == 0) {
     93                         if (mRunningStatus != 0) {
     94                             mBuffer[0] = mRunningStatus;
     95                         }
     96                         mReceiver.send(mBuffer, 0, mCount, timestamp);
     97                         mNeeded = MidiConstants.getBytesPerMessage(mBuffer[0]) - 1;
     98                         mCount = 1;
     99                     }
    100                 }
    101             }
    102             ++offset;
    103         }
    104 
    105         // send any accumulatedSysEx data
    106         if (sysExStartOffset >= 0 && sysExStartOffset < offset) {
    107             mReceiver.send(data, sysExStartOffset,
    108                     offset - sysExStartOffset, timestamp);
    109         }
    110     }
    111 
    112 }
    113