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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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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/**
 * 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 /** "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 /** 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 /** object to notify for new connections from remote endpoint */
    private TCPChannel channel;

    
input stream for underlying single connection /** input stream for underlying single connection */
    private InputStream in;

    
output stream for underlying single connection /** output stream for underlying single connection */
    private OutputStream out;

    
true if underlying connection originated from this endpoint
(used for generating unique connection IDs) /** 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 /** layered stream for reading formatted data from underlying connection */
    private DataInputStream dataIn;

    
layered stream for writing formatted data to underlying connection /** layered stream for writing formatted data to underlying connection */
    private DataOutputStream dataOut;

    
table holding currently open connection IDs and related info /** table holding currently open connection IDs and related info */
    private Hashtable<Integer, MultiplexConnectionInfo> connectionTable = new Hashtable<>(7);

    
number of currently open connections /** number of currently open connections */
    private int numConnections = 0;

    
maximum allowed open connections /** maximum allowed open connections */
    private final static int maxConnections = 256;

    
ID of last connection opened /** ID of last connection opened */
    private int lastID = 0x1001;

    
true if this mechanism is still alive /** 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.
Params:
channel – object to notify when new connection is received
in – input stream of underlying connection
out – output stream of underlying connection
orig – true if this endpoint intiated the underlying
       connection (needs to be set differently at both ends)/**
     * 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.
/**
     * 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.
/**
     * 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.
/**
     * 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.
Params:
info – connection information structure
len – number of more bytes that can be received/**
     * 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.
Params:
info – connection information structure
buf – array containing bytes to send
off – offset of first array index of packet
len – number of bytes in packet to send/**
     * 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.
Params:
info – connection information structure/**
     * 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.
Params:
info – connection information structure/**
     * 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.
/**
     * Shut down connection upon finalization.
     */
    @SuppressWarnings("deprecation")
    protected void finalize() throws Throwable
    {
        super.finalize();
        shutDown();
    }
}