/*

 * Copyright (c) 1996, 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

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 */

package sun.rmi.transport.tcp;

import java.io.*;

import java.net.Socket;

import java.rmi.*;

import sun.rmi.runtime.Log;

import sun.rmi.transport.*;

public class TCPConnection implements Connection {

    private Socket socket;

    private Channel channel;

    private InputStream in = null;

    private OutputStream out = null;

    private long expiration = Long.MAX_VALUE;

    private long lastuse = Long.MIN_VALUE;

    private long roundtrip = 5; // round-trip time for ping

    /**

     * Constructor used for creating a connection to accept call

     * (an input connection)

     */

    TCPConnection(TCPChannel ch, Socket s, InputStream in, OutputStream out)

    {

        socket   = s;

        channel  = ch;

        this.in  = in;

        this.out = out;

    }

    /**

     * Constructor used by subclass when underlying input and output streams

     * are already available.

     */

    TCPConnection(TCPChannel ch, InputStream in, OutputStream out)

    {

        this(ch, null, in, out);

    }

    /**

     * Constructor used when socket is available, but not underlying

     * streams.

     */

    TCPConnection(TCPChannel ch, Socket s)

    {

        this(ch, s, null, null);

    }

    /**

     * Gets the output stream for this connection

     */

    public OutputStream getOutputStream() throws IOException

    {

        if (out == null)

            out = new BufferedOutputStream(socket.getOutputStream());

        return out;

    }

    /**

     * Release the output stream for this connection.

     */

    public void releaseOutputStream() throws IOException

    {

        if (out != null)

            out.flush();

    }

    /**

     * Gets the input stream for this connection.

     */

    public InputStream getInputStream() throws IOException

    {

        if (in == null)

            in = new BufferedInputStream(socket.getInputStream());

        return in;

    }

    /**

     * Release the input stream for this connection.

     */

    public void releaseInputStream()

    {

    }

    /**

     * Determine if this connection can be used for multiple operations.

     * If the socket implements RMISocketInfo, then we can query it about

     * this; otherwise, assume that it does provide a full-duplex

     * persistent connection like java.net.Socket.

     */

    public boolean isReusable()

    {

        return true;

    }

    /**

     * Set the expiration time of this connection.

     * @param time The time at which the time out expires.

     */

    void setExpiration(long time)

    {

        expiration = time;

    }

    /**

     * Set the timestamp at which this connection was last used successfully.

     * The connection will be pinged for liveness if reused long after

     * this time.

     * @param time The time at which the connection was last active.

     */

    void setLastUseTime(long time)

    {

        lastuse = time;

    }

    /**

     * Returns true if the timeout has expired on this connection;

     * otherwise returns false.

     * @param time The current time.

     */

    boolean expired(long time)

    {

        return expiration <= time;

    }

    /**

     * Probes the connection to see if it still alive and connected to

     * a responsive server.  If the connection has been idle for too

     * long, the server is pinged.  ``Too long'' means ``longer than the

     * last ping round-trip time''.

     * <P>

     * This method may misdiagnose a dead connection as live, but it

     * will never misdiagnose a live connection as dead.

     * @return true if the connection and server are recently alive

     */

    public boolean isDead()

    {

        InputStream i;

        OutputStream o;

        // skip ping if recently used within 1 RTT

        long start = System.currentTimeMillis();

        if ((roundtrip > 0) && (start < lastuse + roundtrip))

            return (false);     // still alive and warm

        // Get the streams

        try {

            i = getInputStream();

            o = getOutputStream();

        } catch (IOException e) {

            return (true);      // can't even get a stream, must be very dead

        }

        // Write the ping byte and read the reply byte

        int response = 0;

        try {

            o.write(TransportConstants.Ping);

            o.flush();

            response = i.read();

        } catch (IOException ex) {

            TCPTransport.tcpLog.log(Log.VERBOSE, "exception: ", ex);

            TCPTransport.tcpLog.log(Log.BRIEF, "server ping failed");

            return (true);      // server failed the ping test

        }

        if (response == TransportConstants.PingAck) {

            // save most recent RTT for future use

            roundtrip = (System.currentTimeMillis() - start) * 2;

            // clock-correction may make roundtrip < 0; doesn't matter

            return (false);     // it's alive and 5-by-5

        }

        if (TCPTransport.tcpLog.isLoggable(Log.BRIEF)) {

            TCPTransport.tcpLog.log(Log.BRIEF,

                (response == -1 ? "server has been deactivated" :

                "server protocol error: ping response = " + response));

        }

        return (true);

    }

    /**

     * Close the connection.  */

    public void close() throws IOException

    {

        if (socket != null)

            socket.close();

        else {

            in.close();

            out.close();

        }

    }

    /**

     * Returns the channel for this connection.

     */

    public Channel getChannel()

    {

        return channel;

    }

}