/*
* 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.internal.midi;
/**
* MIDI related constants and static methods.
*/
public final class MidiConstants {
public static final byte STATUS_COMMAND_MASK = (byte) 0xF0;
public static final byte STATUS_CHANNEL_MASK = (byte) 0x0F;
// Channel voice messages.
public static final byte STATUS_NOTE_OFF = (byte) 0x80;
public static final byte STATUS_NOTE_ON = (byte) 0x90;
public static final byte STATUS_POLYPHONIC_AFTERTOUCH = (byte) 0xA0;
public static final byte STATUS_CONTROL_CHANGE = (byte) 0xB0;
public static final byte STATUS_PROGRAM_CHANGE = (byte) 0xC0;
public static final byte STATUS_CHANNEL_PRESSURE = (byte) 0xD0;
public static final byte STATUS_PITCH_BEND = (byte) 0xE0;
// System Common Messages.
public static final byte STATUS_SYSTEM_EXCLUSIVE = (byte) 0xF0;
public static final byte STATUS_MIDI_TIME_CODE = (byte) 0xF1;
public static final byte STATUS_SONG_POSITION = (byte) 0xF2;
public static final byte STATUS_SONG_SELECT = (byte) 0xF3;
public static final byte STATUS_TUNE_REQUEST = (byte) 0xF6;
public static final byte STATUS_END_SYSEX = (byte) 0xF7;
// System Real-Time Messages
public static final byte STATUS_TIMING_CLOCK = (byte) 0xF8;
public static final byte STATUS_START = (byte) 0xFA;
public static final byte STATUS_CONTINUE = (byte) 0xFB;
public static final byte STATUS_STOP = (byte) 0xFC;
public static final byte STATUS_ACTIVE_SENSING = (byte) 0xFE;
public static final byte STATUS_RESET = (byte) 0xFF;
/** Number of bytes in a message nc from 8c to Ec */
public final static int CHANNEL_BYTE_LENGTHS[] = { 3, 3, 3, 3, 2, 2, 3 };
/** Number of bytes in a message Fn from F0 to FF */
public final static int SYSTEM_BYTE_LENGTHS[] = { 1, 2, 3, 2, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1 };
/**
* MIDI messages, except for SysEx, are 1,2 or 3 bytes long.
* You can tell how long a MIDI message is from the first status byte.
* Do not call this for SysEx, which has variable length.
* @param statusByte
* @return number of bytes in a complete message or zero if data byte passed
*/
public static int getBytesPerMessage(byte statusByte) {
// Java bytes are signed so we need to mask off the high bits
// to get a value between 0 and 255.
int statusInt = statusByte & 0xFF;
if (statusInt >= 0xF0) {
// System messages use low nibble for size.
return SYSTEM_BYTE_LENGTHS[statusInt & 0x0F];
} else if(statusInt >= 0x80) {
// Channel voice messages use high nibble for size.
return CHANNEL_BYTE_LENGTHS[(statusInt >> 4) - 8];
} else {
return 0; // data byte
}
}
/**
* @param msg
* @param offset
* @param count
* @return true if the entire message is ActiveSensing commands
*/
public static boolean isAllActiveSensing(byte[] msg, int offset,
int count) {
// Count bytes that are not active sensing.
int goodBytes = 0;
for (int i = 0; i < count; i++) {
byte b = msg[offset + i];
if (b != MidiConstants.STATUS_ACTIVE_SENSING) {
goodBytes++;
}
}
return (goodBytes == 0);
}
// Returns true if this command can be used for running status
public static boolean allowRunningStatus(byte command) {
// only Channel Voice and Channel Mode commands can use running status
return (command >= STATUS_NOTE_OFF && command < STATUS_SYSTEM_EXCLUSIVE);
}
// Returns true if this command cancels running status
public static boolean cancelsRunningStatus(byte command) {
// System Common messages cancel running status
return (command >= STATUS_SYSTEM_EXCLUSIVE && command <= STATUS_END_SYSEX);
}
}