Package org.voltdb.network

Source Code of org.voltdb.network.NIOReadStream

/* This file is part of VoltDB.
* Copyright (C) 2008-2010 VoltDB Inc.
*
* This file contains original code and/or modifications of original code.
* Any modifications made by VoltDB Inc. are licensed under the following
* terms and conditions:
*
* VoltDB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* VoltDB 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with VoltDB.  If not, see <http://www.gnu.org/licenses/>.
*/
/* Copyright (C) 2008
* Evan Jones
* Massachusetts Institute of Technology
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/

package org.voltdb.network;

import java.io.IOException;
import java.nio.channels.ReadableByteChannel;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.ArrayDeque;
import org.voltdb.utils.DBBPool;
import org.voltdb.utils.DBBPool.BBContainer;

/**
Provides a non-blocking stream-like interface on top of the Java NIO ReadableByteChannel. It calls
the underlying read() method only when needed.
*/
public class NIOReadStream {

    NIOReadStream() {
        m_numReadStreams.incrementAndGet();
    }

    /** @returns the number of bytes available to be read. */
    int dataAvailable() {
        return m_totalAvailable;
    }

    int getInt() {
        // TODO: Optimize?
        byte[] intbytes = new byte[4];
        getBytes(intbytes);
        int output = 0;
        for (int i = 0; i < intbytes.length; ++i) {
            output <<= 8;
            output |= (intbytes[i]) & 0xff;
        }
        return output;
    }

    void getBytes(byte[] output) {
        if (m_totalAvailable < output.length) {
            throw new IllegalStateException("Requested " + output.length + " bytes; only have "
                    + m_totalAvailable + " bytes; call tryRead() first");
        }

        int bytesCopied = 0;
        while (bytesCopied < output.length) {
            BBContainer first = m_readBuffers.peekFirst();
            if (first == null) {
                // Steal the write buffer
                m_writeBuffer.b.flip();
                m_readBuffers.add(m_writeBuffer);
                first = m_writeBuffer;
                m_writeBuffer = null;
            }
            assert first.b.remaining() > 0;

            // Copy bytes from first into output
            int bytesRemaining = first.b.remaining();
            int bytesToCopy = output.length - bytesCopied;
            if (bytesToCopy > bytesRemaining) bytesToCopy = bytesRemaining;
            first.b.get(output, bytesCopied, bytesToCopy);
            bytesCopied += bytesToCopy;
            m_totalAvailable -= bytesToCopy;

            if (first.b.remaining() == 0) {
                // read an entire block: move it to the empty buffers list
                m_readBuffers.poll();
                first.discard();
            }
        }

        if (bytesCopied > 0) {
            m_globalAvailable.addAndGet(0 - bytesCopied);
        }
    }

    /**
     * Read at most maxBytes from the network. Will read until the network would
     * block, the stream is closed or the maximum bytes to read is reached.
     * @param maxBytes
     * @return -1 if closed otherwise total buffered bytes. In all cases,
     * data may be buffered in the stream - even when the channel is closed.
     */
    final int read(ReadableByteChannel channel, int maxBytes, final DBBPool pool) throws IOException {
        int bytesRead = 0;
        int lastRead = 1;
        try {
            while (bytesRead < maxBytes && lastRead > 0) {
                if (m_writeBuffer == null) {
                    m_writeBuffer = pool.acquire(BUFFER_SIZE);
                }

                lastRead = channel.read(m_writeBuffer.b);

                // EOF, no data read
                if (lastRead < 0 && bytesRead == 0) {
                    if (m_writeBuffer.b.position() == 0) {
                        m_writeBuffer.discard();
                        m_writeBuffer = null;
                    }
                    return -1;
                }

                //Data read
                if (lastRead > 0) {
                    bytesRead += lastRead;
                    if (!m_writeBuffer.b.hasRemaining()) {
                        m_writeBuffer.b.flip();
                        m_readBuffers.add(m_writeBuffer);
                        m_writeBuffer = null;
                    } else {
                        break;
                    }
                }
            }
        } finally {
            if (bytesRead > 0) {
                m_globalAvailable.addAndGet(bytesRead);
                m_bytesRead.addAndGet(bytesRead);
                m_totalAvailable += bytesRead;
            }
        }

        return bytesRead;
    }

    void shutdown() {
        for (BBContainer c : m_readBuffers) {
            c.discard();
        }
        if (m_writeBuffer != null) {
            m_writeBuffer.discard();
        }
        m_readBuffers.clear();
        m_writeBuffer = null;
        m_numReadStreams.decrementAndGet();
    }

    static final int BUFFER_SIZE = 8192;
    private final ArrayDeque<BBContainer> m_readBuffers = new ArrayDeque<BBContainer>();
    private BBContainer m_writeBuffer = null;
    private int m_totalAvailable = 0;
    private AtomicInteger m_globalAvailable = new AtomicInteger(0);
    private AtomicInteger m_numReadStreams = new AtomicInteger(0);
    private AtomicLong m_bytesRead = new AtomicLong();
    private long m_lastBytesRead = 0;
    long getBytesRead(boolean interval) {
        if (interval) {
            final long bytesRead = m_bytesRead.get();
            final long bytesReadThisTime = bytesRead - m_lastBytesRead;
            m_lastBytesRead = bytesRead;
            return bytesReadThisTime;
        } else {
            return m_bytesRead.get();
        }
    }
}
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