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MidiSynth / src / com.example.android.common.midi /

MidiConstants.java

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/*
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 * Copyright (C) 2015 The Android Open Source Project
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *      http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.example.android.common.midi;
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/**
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 * MIDI related constants and static methods.
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 * These values are defined in the MIDI Standard 1.0
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 * available from the MIDI Manufacturers Association.
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 */
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public class MidiConstants {
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    protected final static String TAG = "MidiTools";
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    public static final byte STATUS_COMMAND_MASK = (byte) 0xF0;
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    public static final byte STATUS_CHANNEL_MASK = (byte) 0x0F;
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    // Channel voice messages.
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    public static final byte STATUS_NOTE_OFF = (byte) 0x80;
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    public static final byte STATUS_NOTE_ON = (byte) 0x90;
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    public static final byte STATUS_POLYPHONIC_AFTERTOUCH = (byte) 0xA0;
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    public static final byte STATUS_CONTROL_CHANGE = (byte) 0xB0;
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    public static final byte STATUS_PROGRAM_CHANGE = (byte) 0xC0;
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    public static final byte STATUS_CHANNEL_PRESSURE = (byte) 0xD0;
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    public static final byte STATUS_PITCH_BEND = (byte) 0xE0;
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    // System Common Messages.
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    public static final byte STATUS_SYSTEM_EXCLUSIVE = (byte) 0xF0;
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    public static final byte STATUS_MIDI_TIME_CODE = (byte) 0xF1;
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    public static final byte STATUS_SONG_POSITION = (byte) 0xF2;
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    public static final byte STATUS_SONG_SELECT = (byte) 0xF3;
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    public static final byte STATUS_TUNE_REQUEST = (byte) 0xF6;
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    public static final byte STATUS_END_SYSEX = (byte) 0xF7;
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    // System Real-Time Messages
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    public static final byte STATUS_TIMING_CLOCK = (byte) 0xF8;
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    public static final byte STATUS_START = (byte) 0xFA;
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    public static final byte STATUS_CONTINUE = (byte) 0xFB;
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    public static final byte STATUS_STOP = (byte) 0xFC;
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    public static final byte STATUS_ACTIVE_SENSING = (byte) 0xFE;
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    public static final byte STATUS_RESET = (byte) 0xFF;
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    /** Number of bytes in a message nc from 8c to Ec */
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    public final static int CHANNEL_BYTE_LENGTHS[] = { 3, 3, 3, 3, 2, 2, 3 };
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    /** Number of bytes in a message Fn from F0 to FF */
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    public final static int SYSTEM_BYTE_LENGTHS[] = { 1, 2, 3, 2, 1, 1, 1, 1, 1,
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            1, 1, 1, 1, 1, 1, 1 };
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    /**
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     * MIDI messages, except for SysEx, are 1,2 or 3 bytes long.
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     * You can tell how long a MIDI message is from the first status byte.
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     * Do not call this for SysEx, which has variable length.
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     * @param statusByte
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     * @return number of bytes in a complete message, zero if data byte passed
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     */
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    public static int getBytesPerMessage(byte statusByte) {
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        // Java bytes are signed so we need to mask off the high bits
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        // to get a value between 0 and 255.
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        int statusInt = statusByte & 0xFF;
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        if (statusInt >= 0xF0) {
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            // System messages use low nibble for size.
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            return SYSTEM_BYTE_LENGTHS[statusInt & 0x0F];
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        } else if(statusInt >= 0x80) {
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            // Channel voice messages use high nibble for size.
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            return CHANNEL_BYTE_LENGTHS[(statusInt >> 4) - 8];
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        } else {
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            return 0; // data byte
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        }
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    }
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    /**
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     * @param msg
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     * @param offset
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     * @param count
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     * @return true if the entire message is ActiveSensing commands
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     */
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    public static boolean isAllActiveSensing(byte[] msg, int offset,
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            int count) {
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        // Count bytes that are not active sensing.
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        int goodBytes = 0;
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        for (int i = 0; i < count; i++) {
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            byte b = msg[offset + i];
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            if (b != MidiConstants.STATUS_ACTIVE_SENSING) {
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                goodBytes++;
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            }
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        }
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        return (goodBytes == 0);
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    }
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}
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