org.codice.alliance.video.stream.mpegts.netty.StartCode.java Source code

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Here is the source code for org.codice.alliance.video.stream.mpegts.netty.StartCode.java

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/**
 * Copyright (c) Codice Foundation
 * <p/>
 * This is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser
 * General Public License as published by the Free Software Foundation, either version 3 of the
 * License, or any later version.
 * <p/>
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details. A copy of the GNU Lesser General Public License
 * is distributed along with this program and can be found at
 * <http://www.gnu.org/licenses/lgpl.html>.
 */
package org.codice.alliance.video.stream.mpegts.netty;

import io.netty.buffer.ByteBufProcessor;

/**
 * A start code is the byte sequence 0x00 0x00 0x01 0xXX, where XX is any byte value. When
 * used with ByteBuf.forEachByte, this caller will get the index position of the last byte of
 * the start code.
 */
public class StartCode implements ByteBufProcessor {

    private States currentState = States.START;

    public void init() {
        currentState = States.START;
    }

    @Override
    public boolean process(byte currentByte) throws Exception {

        switch (currentState) {
        case START:
            switch (currentByte) {
            case 0:
                currentState = States.S1;
                break;
            default:
                // ignore current byte
            }
            break;
        case S1:
            switch (currentByte) {
            case 0:
                currentState = States.S2;
                break;
            default:
                currentState = States.START;
                break;
            }
            break;
        case S2:
            switch (currentByte) {
            case 0:
                // don't change states
                break;
            case 1:
                currentState = States.S3;
                break;
            default:
                currentState = States.START;
                break;
            }
            break;
        case S3:
            currentState = States.START;
            return false;
        default:
            assert false : "this should never happen!";
        }

        return true;
    }

    private enum States {
        START, S1, S2, S3
    }

}