/*

 * 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.util.*;

import java.rmi.server.LogStream;

import java.security.PrivilegedAction;

import sun.rmi.runtime.Log;

/**

 * ConnectionMultiplexer manages the transparent multiplexing of

 * multiple virtual connections from one endpoint to another through

 * one given real connection to that endpoint.  The input and output

 * streams for the underlying real connection must be supplied.

 * A callback object is also supplied to be informed of new virtual

 * connections opened by the remote endpoint.  After creation, the

 * run() method must be called in a thread created for demultiplexing

 * the connections.  The openConnection() method is called to

 * initiate a virtual connection from this endpoint.

 *

 * @author Peter Jones

 */

@SuppressWarnings("deprecation")

final class ConnectionMultiplexer {

    /** "multiplex" log level */

    static int logLevel = LogStream.parseLevel(getLogLevel());

    private static String getLogLevel() {

        return java.security.AccessController.doPrivileged(

           (PrivilegedAction<String>) () -> System.getProperty("sun.rmi.transport.tcp.multiplex.logLevel"));

    }

    /* multiplex system log */

    static final Log multiplexLog =

        Log.getLog("sun.rmi.transport.tcp.multiplex",

                   "multiplex", ConnectionMultiplexer.logLevel);

    /** multiplexing protocol operation codes */

    private final static int OPEN     = 0xE1;

    private final static int CLOSE    = 0xE2;

    private final static int CLOSEACK = 0xE3;

    private final static int REQUEST  = 0xE4;

    private final static int TRANSMIT = 0xE5;

    /** object to notify for new connections from remote endpoint */

    private TCPChannel channel;

    /** input stream for underlying single connection */

    private InputStream in;

    /** output stream for underlying single connection */

    private OutputStream out;

    /** true if underlying connection originated from this endpoint

        (used for generating unique connection IDs) */

    private boolean orig;

    /** layered stream for reading formatted data from underlying connection */

    private DataInputStream dataIn;

    /** layered stream for writing formatted data to underlying connection */

    private DataOutputStream dataOut;

    /** table holding currently open connection IDs and related info */

    private Hashtable<Integer, MultiplexConnectionInfo> connectionTable = new Hashtable<>(7);

    /** number of currently open connections */

    private int numConnections = 0;

    /** maximum allowed open connections */

    private final static int maxConnections = 256;

    /** ID of last connection opened */

    private int lastID = 0x1001;

    /** true if this mechanism is still alive */

    private boolean alive = true;

    /**

     * Create a new ConnectionMultiplexer using the given underlying

     * input/output stream pair.  The run method must be called

     * (possibly on a new thread) to handle the demultiplexing.

     * @param channel object to notify when new connection is received

     * @param in input stream of underlying connection

     * @param out output stream of underlying connection

     * @param orig true if this endpoint intiated the underlying

     *        connection (needs to be set differently at both ends)

     */

    public ConnectionMultiplexer(

        TCPChannel    channel,

        InputStream   in,

        OutputStream  out,

        boolean       orig)

    {

        this.channel = channel;

        this.in      = in;

        this.out     = out;

        this.orig    = orig;

        dataIn = new DataInputStream(in);

        dataOut = new DataOutputStream(out);

    }

    /**

     * Process multiplexing protocol received from underlying connection.

     */

    public void run() throws IOException

    {

        try {

            int op, id, length;

            MultiplexConnectionInfo info;

            while (true) {

                // read next op code from remote endpoint

                op = dataIn.readUnsignedByte();

                switch (op) {

                // remote endpoint initiating new connection

                case OPEN:

                    id = dataIn.readUnsignedShort();

                    if (multiplexLog.isLoggable(Log.VERBOSE)) {

                        multiplexLog.log(Log.VERBOSE, "operation  OPEN " + id);

                    }

                    info = connectionTable.get(id);

                    if (info != null)

                        throw new IOException(

                            "OPEN: Connection ID already exists");

                    info = new MultiplexConnectionInfo(id);

                    info.in = new MultiplexInputStream(this, info, 2048);

                    info.out = new MultiplexOutputStream(this, info, 2048);

                    synchronized (connectionTable) {

                        connectionTable.put(id, info);

                        ++ numConnections;

                    }

                    sun.rmi.transport.Connection conn;

                    conn = new TCPConnection(channel, info.in, info.out);

                    channel.acceptMultiplexConnection(conn);

                    break;

                // remote endpoint closing connection

                case CLOSE:

                    id = dataIn.readUnsignedShort();

                    if (multiplexLog.isLoggable(Log.VERBOSE)) {

                        multiplexLog.log(Log.VERBOSE, "operation  CLOSE " + id);

                    }

                    info = connectionTable.get(id);

                    if (info == null)

                        throw new IOException(

                            "CLOSE: Invalid connection ID");

                    info.in.disconnect();

                    info.out.disconnect();

                    if (!info.closed)

                        sendCloseAck(info);

                    synchronized (connectionTable) {

                        connectionTable.remove(id);

                        -- numConnections;

                    }

                    break;

                // remote endpoint acknowledging close of connection

                case CLOSEACK:

                    id = dataIn.readUnsignedShort();

                    if (multiplexLog.isLoggable(Log.VERBOSE)) {

                        multiplexLog.log(Log.VERBOSE,

                            "operation  CLOSEACK " + id);

                    }

                    info = connectionTable.get(id);

                    if (info == null)

                        throw new IOException(

                            "CLOSEACK: Invalid connection ID");

                    if (!info.closed)

                        throw new IOException(

                            "CLOSEACK: Connection not closed");

                    info.in.disconnect();

                    info.out.disconnect();

                    synchronized (connectionTable) {

                        connectionTable.remove(id);

                        -- numConnections;

                    }

                    break;

                // remote endpoint declaring additional bytes receivable

                case REQUEST:

                    id = dataIn.readUnsignedShort();

                    info = connectionTable.get(id);

                    if (info == null)

                        throw new IOException(

                            "REQUEST: Invalid connection ID");

                    length = dataIn.readInt();

                    if (multiplexLog.isLoggable(Log.VERBOSE)) {

                        multiplexLog.log(Log.VERBOSE,

                            "operation  REQUEST " + id + ": " + length);

                    }

                    info.out.request(length);

                    break;

                // remote endpoint transmitting data packet

                case TRANSMIT:

                    id = dataIn.readUnsignedShort();

                    info = connectionTable.get(id);

                    if (info == null)

                        throw new IOException("SEND: Invalid connection ID");

                    length = dataIn.readInt();

                    if (multiplexLog.isLoggable(Log.VERBOSE)) {

                        multiplexLog.log(Log.VERBOSE,

                            "operation  TRANSMIT " + id + ": " + length);

                    }

                    info.in.receive(length, dataIn);

                    break;

                default:

                    throw new IOException("Invalid operation: " +

                                          Integer.toHexString(op));

                }

            }

        } finally {

            shutDown();

        }

    }

    /**

     * Initiate a new multiplexed connection through the underlying

     * connection.

     */

    public synchronized TCPConnection openConnection() throws IOException

    {

        // generate ID that should not be already used

        // If all possible 32768 IDs are used,

        // this method will block searching for a new ID forever.

        int id;

        do {

            lastID = (++ lastID) & 0x7FFF;

            id = lastID;

            // The orig flag (copied to the high bit of the ID) is used

            // to have two distinct ranges to choose IDs from for the

            // two endpoints.

            if (orig)

                id |= 0x8000;

        } while (connectionTable.get(id) != null);

        // create multiplexing streams and bookkeeping information

        MultiplexConnectionInfo info = new MultiplexConnectionInfo(id);

        info.in = new MultiplexInputStream(this, info, 2048);

        info.out = new MultiplexOutputStream(this, info, 2048);

        // add to connection table if multiplexer has not died

        synchronized (connectionTable) {

            if (!alive)

                throw new IOException("Multiplexer connection dead");

            if (numConnections >= maxConnections)

                throw new IOException("Cannot exceed " + maxConnections +

                    " simultaneous multiplexed connections");

            connectionTable.put(id, info);

            ++ numConnections;

        }

        // inform remote endpoint of new connection

        synchronized (dataOut) {

            try {

                dataOut.writeByte(OPEN);

                dataOut.writeShort(id);

                dataOut.flush();

            } catch (IOException e) {

                multiplexLog.log(Log.BRIEF, "exception: ", e);

                shutDown();

                throw e;

            }

        }

        return new TCPConnection(channel, info.in, info.out);

    }

    /**

     * Shut down all connections and clean up.

     */

    public void shutDown()

    {

        // inform all associated streams

        synchronized (connectionTable) {

            // return if multiplexer already officially dead

            if (!alive)

                return;

            alive = false;

            Enumeration<MultiplexConnectionInfo> enum_ =

                    connectionTable.elements();

            while (enum_.hasMoreElements()) {

                MultiplexConnectionInfo info = enum_.nextElement();

                info.in.disconnect();

                info.out.disconnect();

            }

            connectionTable.clear();

            numConnections = 0;

        }

        // close underlying connection, if possible (and not already done)

        try {

            in.close();

        } catch (IOException e) {

        }

        try {

            out.close();

        } catch (IOException e) {

        }

    }

    /**

     * Send request for more data on connection to remote endpoint.

     * @param info connection information structure

     * @param len number of more bytes that can be received

     */

    void sendRequest(MultiplexConnectionInfo info, int len) throws IOException

    {

        synchronized (dataOut) {

            if (alive && !info.closed)

                try {

                    dataOut.writeByte(REQUEST);

                    dataOut.writeShort(info.id);

                    dataOut.writeInt(len);

                    dataOut.flush();

                } catch (IOException e) {

                    multiplexLog.log(Log.BRIEF, "exception: ", e);

                    shutDown();

                    throw e;

                }

        }

    }

    /**

     * Send packet of requested data on connection to remote endpoint.

     * @param info connection information structure

     * @param buf array containing bytes to send

     * @param off offset of first array index of packet

     * @param len number of bytes in packet to send

     */

    void sendTransmit(MultiplexConnectionInfo info,

                      byte buf[], int off, int len) throws IOException

    {

        synchronized (dataOut) {

            if (alive && !info.closed)

                try {

                    dataOut.writeByte(TRANSMIT);

                    dataOut.writeShort(info.id);

                    dataOut.writeInt(len);

                    dataOut.write(buf, off, len);

                    dataOut.flush();

                } catch (IOException e) {

                    multiplexLog.log(Log.BRIEF, "exception: ", e);

                    shutDown();

                    throw e;

                }

        }

    }

    /**

     * Inform remote endpoint that connection has been closed.

     * @param info connection information structure

     */

    void sendClose(MultiplexConnectionInfo info) throws IOException

    {

        info.out.disconnect();

        synchronized (dataOut) {

            if (alive && !info.closed)

                try {

                    dataOut.writeByte(CLOSE);

                    dataOut.writeShort(info.id);

                    dataOut.flush();

                    info.closed = true;

                } catch (IOException e) {

                    multiplexLog.log(Log.BRIEF, "exception: ", e);

                    shutDown();

                    throw e;

                }

        }

    }

    /**

     * Acknowledge remote endpoint's closing of connection.

     * @param info connection information structure

     */

    void sendCloseAck(MultiplexConnectionInfo info) throws IOException

    {

        synchronized (dataOut) {

            if (alive && !info.closed)

                try {

                    dataOut.writeByte(CLOSEACK);

                    dataOut.writeShort(info.id);

                    dataOut.flush();

                    info.closed = true;

                } catch (IOException e) {

                    multiplexLog.log(Log.BRIEF, "exception: ", e);

                    shutDown();

                    throw e;

                }

        }

    }

    /**

     * Shut down connection upon finalization.

     */

    protected void finalize() throws Throwable

    {

        super.finalize();

        shutDown();

    }

}