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.android.internal.midi; 18 19 /** 20 * MIDI related constants and static methods. 21 */ 22 public final class MidiConstants { 23 public static final byte STATUS_COMMAND_MASK = (byte) 0xF0; 24 public static final byte STATUS_CHANNEL_MASK = (byte) 0x0F; 25 26 // Channel voice messages. 27 public static final byte STATUS_NOTE_OFF = (byte) 0x80; 28 public static final byte STATUS_NOTE_ON = (byte) 0x90; 29 public static final byte STATUS_POLYPHONIC_AFTERTOUCH = (byte) 0xA0; 30 public static final byte STATUS_CONTROL_CHANGE = (byte) 0xB0; 31 public static final byte STATUS_PROGRAM_CHANGE = (byte) 0xC0; 32 public static final byte STATUS_CHANNEL_PRESSURE = (byte) 0xD0; 33 public static final byte STATUS_PITCH_BEND = (byte) 0xE0; 34 35 // System Common Messages. 36 public static final byte STATUS_SYSTEM_EXCLUSIVE = (byte) 0xF0; 37 public static final byte STATUS_MIDI_TIME_CODE = (byte) 0xF1; 38 public static final byte STATUS_SONG_POSITION = (byte) 0xF2; 39 public static final byte STATUS_SONG_SELECT = (byte) 0xF3; 40 public static final byte STATUS_TUNE_REQUEST = (byte) 0xF6; 41 public static final byte STATUS_END_SYSEX = (byte) 0xF7; 42 43 // System Real-Time Messages 44 public static final byte STATUS_TIMING_CLOCK = (byte) 0xF8; 45 public static final byte STATUS_START = (byte) 0xFA; 46 public static final byte STATUS_CONTINUE = (byte) 0xFB; 47 public static final byte STATUS_STOP = (byte) 0xFC; 48 public static final byte STATUS_ACTIVE_SENSING = (byte) 0xFE; 49 public static final byte STATUS_RESET = (byte) 0xFF; 50 51 /** Number of bytes in a message nc from 8c to Ec */ 52 public final static int CHANNEL_BYTE_LENGTHS[] = { 3, 3, 3, 3, 2, 2, 3 }; 53 54 /** Number of bytes in a message Fn from F0 to FF */ 55 public final static int SYSTEM_BYTE_LENGTHS[] = { 1, 2, 3, 2, 1, 1, 1, 1, 1, 56 1, 1, 1, 1, 1, 1, 1 }; 57 58 59 /** 60 * MIDI messages, except for SysEx, are 1,2 or 3 bytes long. 61 * You can tell how long a MIDI message is from the first status byte. 62 * Do not call this for SysEx, which has variable length. 63 * @param statusByte 64 * @return number of bytes in a complete message or zero if data byte passed 65 */ getBytesPerMessage(byte statusByte)66 public static int getBytesPerMessage(byte statusByte) { 67 // Java bytes are signed so we need to mask off the high bits 68 // to get a value between 0 and 255. 69 int statusInt = statusByte & 0xFF; 70 if (statusInt >= 0xF0) { 71 // System messages use low nibble for size. 72 return SYSTEM_BYTE_LENGTHS[statusInt & 0x0F]; 73 } else if(statusInt >= 0x80) { 74 // Channel voice messages use high nibble for size. 75 return CHANNEL_BYTE_LENGTHS[(statusInt >> 4) - 8]; 76 } else { 77 return 0; // data byte 78 } 79 } 80 81 82 /** 83 * @param msg 84 * @param offset 85 * @param count 86 * @return true if the entire message is ActiveSensing commands 87 */ isAllActiveSensing(byte[] msg, int offset, int count)88 public static boolean isAllActiveSensing(byte[] msg, int offset, 89 int count) { 90 // Count bytes that are not active sensing. 91 int goodBytes = 0; 92 for (int i = 0; i < count; i++) { 93 byte b = msg[offset + i]; 94 if (b != MidiConstants.STATUS_ACTIVE_SENSING) { 95 goodBytes++; 96 } 97 } 98 return (goodBytes == 0); 99 } 100 101 // Returns true if this command can be used for running status allowRunningStatus(byte command)102 public static boolean allowRunningStatus(byte command) { 103 // only Channel Voice and Channel Mode commands can use running status 104 return (command >= STATUS_NOTE_OFF && command < STATUS_SYSTEM_EXCLUSIVE); 105 } 106 107 // Returns true if this command cancels running status cancelsRunningStatus(byte command)108 public static boolean cancelsRunningStatus(byte command) { 109 // System Common messages cancel running status 110 return (command >= STATUS_SYSTEM_EXCLUSIVE && command <= STATUS_END_SYSEX); 111 } 112 } 113