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VoltDB server libraries
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/* This file is part of VoltDB.
 * Copyright (C) 2008-2018 VoltDB Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with VoltDB.  If not, see .
 */

package org.voltcore.network;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.concurrent.atomic.AtomicLong;

import io.netty.buffer.CompositeByteBuf;

public abstract class VoltProtocolHandler implements InputHandler {
    /** VoltProtocolPorts each have a unique id */
    private static AtomicLong m_globalConnectionCounter = new AtomicLong(0);

    /** The distinct exception class allows better logging of these unexpected errors. */
    class BadMessageLength extends IOException {
        private static final long serialVersionUID = 8547352379044459911L;
        public BadMessageLength(String string) {
            super(string);
        }
    }

    /** serial number of this VoltPort */
    private final long m_connectionId;
    private int m_nextLength;

    public VoltProtocolHandler() {
        m_connectionId = m_globalConnectionCounter.incrementAndGet();
    }

    public static long getNextConnectionId() {
        return m_globalConnectionCounter.incrementAndGet();
    }

    @Override
    public ByteBuffer retrieveNextMessage(final NIOReadStream inputStream) throws BadMessageLength {

        /*
         * Note that access to the read stream is not synchronized. In this application
         * the VoltPort will invoke this input handler to interact with the read stream guaranteeing
         * thread safety. That said the Connection interface does allow other parts of the application
         * access to the read stream.
         */
        ByteBuffer result = null;

        if (m_nextLength == 0 && inputStream.dataAvailable() > (Integer.SIZE/8)) {
            m_nextLength = inputStream.getInt();
            checkMessageLength();
        }
        if (m_nextLength > 0 && inputStream.dataAvailable() >= m_nextLength) {
            result = ByteBuffer.allocate(m_nextLength);
            // Copy read buffers to result, move read buffers back to memory pool
            inputStream.getBytes(result.array());
            m_nextLength = 0;
        }
        return result;
    }

    @Override
    public ByteBuffer retrieveNextMessage(CompositeByteBuf inputBB) throws BadMessageLength {
        ByteBuffer result = null;
        if (m_nextLength == 0 && inputBB.readableBytes() > (Integer.SIZE/8)) {
            m_nextLength = inputBB.readInt();
            checkMessageLength();
        }

        if (m_nextLength > 0 && inputBB.readableBytes() >= m_nextLength) {
            result = ByteBuffer.allocate(m_nextLength);
            // Copy read buffers to result, move read buffers back to memory pool
            inputBB.readBytes(result);
            m_nextLength = 0;
        }
        return result;
    }

    private void checkMessageLength() throws BadMessageLength {
        if (m_nextLength < 1) {
            throw new BadMessageLength(
                    "Next message length is " + m_nextLength + " which is less than 1 and is nonsense");
        }
        if (m_nextLength > VoltPort.MAX_MESSAGE_LENGTH) {
            throw new BadMessageLength(
                    "Next message length is " + m_nextLength + " which is greater then the hard coded " +
                    "max of " + VoltPort.MAX_MESSAGE_LENGTH + ". Break up the work into smaller chunks (2 megabytes is reasonable) " +
                    "and send as multiple messages or stored procedure invocations");
        }
        assert m_nextLength > 0;
    }

    @Override
    public void started(Connection c) {
    }

    @Override
    public void starting(Connection c) {
    }

    @Override
    public void stopped(Connection c) {
    }

    @Override
    public void stopping(Connection c) {
    }

    @Override
    public long connectionId() {
        return m_connectionId;
    }

    public int getNextMessageLength() {
        return m_nextLength;
    }

}