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 * Copyright (c) 1995, 2016, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.FileDescriptor;
import java.util.Set;

/**
 * The abstract class {@code SocketImpl} is a common superclass
 * of all classes that actually implement sockets. It is used to
 * create both client and server sockets.
 * <p>
 * A "plain" socket implements these methods exactly as
 * described, without attempting to go through a firewall or proxy.
 *
 * @author unascribed
 * @since 1.0
 */
public abstract class SocketImpl implements SocketOptions {
 /**
 * The actual Socket object.
 */
 Socket socket = null;
 ServerSocket serverSocket = null;

 /**
 * The file descriptor object for this socket.
 */
 protected FileDescriptor fd;

 /**
 * The IP address of the remote end of this socket.
 */
 protected InetAddress address;

 /**
 * The port number on the remote host to which this socket is connected.
 */
 protected int port;

 /**
 * The local port number to which this socket is connected.
 */
 protected int localport;

 /**
 * Creates either a stream or a datagram socket.
 *
 * @param stream if {@code true}, create a stream socket;
 * otherwise, create a datagram socket.
 * @exception IOException if an I/O error occurs while creating the
 * socket.
 */
 protected abstract void create(boolean stream) throws IOException;

 /**
 * Connects this socket to the specified port on the named host.
 *
 * @param host the name of the remote host.
 * @param port the port number.
 * @exception IOException if an I/O error occurs when connecting to the
 * remote host.
 */
 protected abstract void connect(String host, int port) throws IOException;

 /**
 * Connects this socket to the specified port number on the specified host.
 *
 * @param address the IP address of the remote host.
 * @param port the port number.
 * @exception IOException if an I/O error occurs when attempting a
 * connection.
 */
 protected abstract void connect(InetAddress address, int port) throws IOException;

 /**
 * Connects this socket to the specified port number on the specified host.
 * A timeout of zero is interpreted as an infinite timeout. The connection
 * will then block until established or an error occurs.
 *
 * @param address the Socket address of the remote host.
 * @param timeout the timeout value, in milliseconds, or zero for no timeout.
 * @exception IOException if an I/O error occurs when attempting a
 * connection.
 * @since 1.4
 */
 protected abstract void connect(SocketAddress address, int timeout) throws IOException;

 /**
 * Binds this socket to the specified local IP address and port number.
 *
 * @param host an IP address that belongs to a local interface.
 * @param port the port number.
 * @exception IOException if an I/O error occurs when binding this socket.
 */
 protected abstract void bind(InetAddress host, int port) throws IOException;

 /**
 * Sets the maximum queue length for incoming connection indications
 * (a request to connect) to the {@code count} argument. If a
 * connection indication arrives when the queue is full, the
 * connection is refused.
 *
 * @param backlog the maximum length of the queue.
 * @exception IOException if an I/O error occurs when creating the queue.
 */
 protected abstract void listen(int backlog) throws IOException;

 /**
 * Accepts a connection.
 *
 * @param s the accepted connection.
 * @exception IOException if an I/O error occurs when accepting the
 * connection.
 */
 protected abstract void accept(SocketImpl s) throws IOException;

 /**
 * Returns an input stream for this socket.
 *
 * @return a stream for reading from this socket.
 * @exception IOException if an I/O error occurs when creating the
 * input stream.
 */
 protected abstract InputStream getInputStream() throws IOException;

 /**
 * Returns an output stream for this socket.
 *
 * @return an output stream for writing to this socket.
 * @exception IOException if an I/O error occurs when creating the
 * output stream.
 */
 protected abstract OutputStream getOutputStream() throws IOException;

 /**
 * Returns the number of bytes that can be read from this socket
 * without blocking.
 *
 * @return the number of bytes that can be read from this socket
 * without blocking.
 * @exception IOException if an I/O error occurs when determining the
 * number of bytes available.
 */
 protected abstract int available() throws IOException;

 /**
 * Closes this socket.
 *
 * @exception IOException if an I/O error occurs when closing this socket.
 */
 protected abstract void close() throws IOException;

 /**
 * Places the input stream for this socket at "end of stream".
 * Any data sent to this socket is acknowledged and then
 * silently discarded.
 *
 * If you read from a socket input stream after invoking this method on the
 * socket, the stream's {@code available} method will return 0, and its
 * {@code read} methods will return {@code -1} (end of stream).
 *
 * @exception IOException if an I/O error occurs when shutting down this
 * socket.
 * @see java.net.Socket#shutdownOutput()
 * @see java.net.Socket#close()
 * @see java.net.Socket#setSoLinger(boolean, int)
 * @since 1.3
 */
 protected void shutdownInput() throws IOException {
 throw new IOException("Method not implemented!");
 }

 /**
 * Disables the output stream for this socket.
 * For a TCP socket, any previously written data will be sent
 * followed by TCP's normal connection termination sequence.
 *
 * If you write to a socket output stream after invoking
 * shutdownOutput() on the socket, the stream will throw
 * an IOException.
 *
 * @exception IOException if an I/O error occurs when shutting down this
 * socket.
 * @see java.net.Socket#shutdownInput()
 * @see java.net.Socket#close()
 * @see java.net.Socket#setSoLinger(boolean, int)
 * @since 1.3
 */
 protected void shutdownOutput() throws IOException {
 throw new IOException("Method not implemented!");
 }

 /**
 * Returns the value of this socket's {@code fd} field.
 *
 * @return the value of this socket's {@code fd} field.
 * @see java.net.SocketImpl#fd
 */
 protected FileDescriptor getFileDescriptor() {
 return fd;
 }

 /**
 * Returns the value of this socket's {@code address} field.
 *
 * @return the value of this socket's {@code address} field.
 * @see java.net.SocketImpl#address
 */
 protected InetAddress getInetAddress() {
 return address;
 }

 /**
 * Returns the value of this socket's {@code port} field.
 *
 * @return the value of this socket's {@code port} field.
 * @see java.net.SocketImpl#port
 */
 protected int getPort() {
 return port;
 }

 /**
 * Returns whether or not this SocketImpl supports sending
 * urgent data. By default, false is returned
 * unless the method is overridden in a sub-class
 *
 * @return true if urgent data supported
 * @see java.net.SocketImpl#address
 * @since 1.4
 */
 protected boolean supportsUrgentData () {
 return false; // must be overridden in sub-class
 }

 /**
 * Send one byte of urgent data on the socket.
 * The byte to be sent is the low eight bits of the parameter
 * @param data The byte of data to send
 * @exception IOException if there is an error
 * sending the data.
 * @since 1.4
 */
 protected abstract void sendUrgentData (int data) throws IOException;

 /**
 * Returns the value of this socket's {@code localport} field.
 *
 * @return the value of this socket's {@code localport} field.
 * @see java.net.SocketImpl#localport
 */
 protected int getLocalPort() {
 return localport;
 }

 void setSocket(Socket soc) {
 this.socket = soc;
 }

 Socket getSocket() {
 return socket;
 }

 void setServerSocket(ServerSocket soc) {
 this.serverSocket = soc;
 }

 ServerSocket getServerSocket() {
 return serverSocket;
 }

 /**
 * Returns the address and port of this socket as a {@code String}.
 *
 * @return a string representation of this socket.
 */
 public String toString() {
 return "Socket[addr=" + getInetAddress() +
 ",port=" + getPort() + ",localport=" + getLocalPort() + "]";
 }

 void reset() throws IOException {
 address = null;
 port = 0;
 localport = 0;
 }

 /**
 * Sets performance preferences for this socket.
 *
 * <p> Sockets use the TCP/IP protocol by default. Some implementations
 * may offer alternative protocols which have different performance
 * characteristics than TCP/IP. This method allows the application to
 * express its own preferences as to how these tradeoffs should be made
 * when the implementation chooses from the available protocols.
 *
 * <p> Performance preferences are described by three integers
 * whose values indicate the relative importance of short connection time,
 * low latency, and high bandwidth. The absolute values of the integers
 * are irrelevant; in order to choose a protocol the values are simply
 * compared, with larger values indicating stronger preferences. Negative
 * values represent a lower priority than positive values. If the
 * application prefers short connection time over both low latency and high
 * bandwidth, for example, then it could invoke this method with the values
 * {@code (1, 0, 0)}. If the application prefers high bandwidth above low
 * latency, and low latency above short connection time, then it could
 * invoke this method with the values {@code (0, 1, 2)}.
 *
 * By default, this method does nothing, unless it is overridden in
 * a sub-class.
 *
 * @param connectionTime
 * An {@code int} expressing the relative importance of a short
 * connection time
 *
 * @param latency
 * An {@code int} expressing the relative importance of low
 * latency
 *
 * @param bandwidth
 * An {@code int} expressing the relative importance of high
 * bandwidth
 *
 * @since 1.5
 */
 protected void setPerformancePreferences(int connectionTime,
 int latency,
 int bandwidth)
 {
 /* Not implemented yet */
 }

 /**
 * Called to set a socket option.
 *
 * @param <T> The type of the socket option value
 * @param name The socket option
 *
 * @param value The value of the socket option. A value of {@code null}
 * may be valid for some options.
 *
 * @throws UnsupportedOperationException if the SocketImpl does not
 * support the option
 *
 * @throws IOException if an I/O error occurs, or if the socket is closed.
 *
 * @since 9
 */
 protected <T> void setOption(SocketOption<T> name, T value) throws IOException {
 if (name == StandardSocketOptions.SO_KEEPALIVE &&
 (getSocket() != null)) {
 setOption(SocketOptions.SO_KEEPALIVE, value);
 } else if (name == StandardSocketOptions.SO_SNDBUF &&
 (getSocket() != null)) {
 setOption(SocketOptions.SO_SNDBUF, value);
 } else if (name == StandardSocketOptions.SO_RCVBUF) {
 setOption(SocketOptions.SO_RCVBUF, value);
 } else if (name == StandardSocketOptions.SO_REUSEADDR) {
 setOption(SocketOptions.SO_REUSEADDR, value);
 } else if (name == StandardSocketOptions.SO_REUSEPORT &&
 supportedOptions().contains(name)) {
 setOption(SocketOptions.SO_REUSEPORT, value);
 } else if (name == StandardSocketOptions.SO_LINGER &&
 (getSocket() != null)) {
 setOption(SocketOptions.SO_LINGER, value);
 } else if (name == StandardSocketOptions.IP_TOS) {
 setOption(SocketOptions.IP_TOS, value);
 } else if (name == StandardSocketOptions.TCP_NODELAY &&
 (getSocket() != null)) {
 setOption(SocketOptions.TCP_NODELAY, value);
 } else {
 throw new UnsupportedOperationException("unsupported option");
 }
 }

 /**
 * Called to get a socket option.
 *
 * @param <T> The type of the socket option value
 * @param name The socket option
 *
 * @return the value of the named option
 *
 * @throws UnsupportedOperationException if the SocketImpl does not
 * support the option.
 *
 * @throws IOException if an I/O error occurs, or if the socket is closed.
 *
 * @since 9
 */
 @SuppressWarnings("unchecked")
 protected <T> T getOption(SocketOption<T> name) throws IOException {
 if (name == StandardSocketOptions.SO_KEEPALIVE &&
 (getSocket() != null)) {
 return (T)getOption(SocketOptions.SO_KEEPALIVE);
 } else if (name == StandardSocketOptions.SO_SNDBUF &&
 (getSocket() != null)) {
 return (T)getOption(SocketOptions.SO_SNDBUF);
 } else if (name == StandardSocketOptions.SO_RCVBUF) {
 return (T)getOption(SocketOptions.SO_RCVBUF);
 } else if (name == StandardSocketOptions.SO_REUSEADDR) {
 return (T)getOption(SocketOptions.SO_REUSEADDR);
 } else if (name == StandardSocketOptions.SO_REUSEPORT &&
 supportedOptions().contains(name)) {
 return (T)getOption(SocketOptions.SO_REUSEPORT);
 } else if (name == StandardSocketOptions.SO_LINGER &&
 (getSocket() != null)) {
 return (T)getOption(SocketOptions.SO_LINGER);
 } else if (name == StandardSocketOptions.IP_TOS) {
 return (T)getOption(SocketOptions.IP_TOS);
 } else if (name == StandardSocketOptions.TCP_NODELAY &&
 (getSocket() != null)) {
 return (T)getOption(SocketOptions.TCP_NODELAY);
 } else {
 throw new UnsupportedOperationException("unsupported option");
 }
 }

 private static final Set<SocketOption<?>> socketOptions;

 private static final Set<SocketOption<?>> serverSocketOptions;

 static {
 socketOptions = Set.of(StandardSocketOptions.SO_KEEPALIVE,
 StandardSocketOptions.SO_SNDBUF,
 StandardSocketOptions.SO_RCVBUF,
 StandardSocketOptions.SO_REUSEADDR,
 StandardSocketOptions.SO_LINGER,
 StandardSocketOptions.IP_TOS,
 StandardSocketOptions.TCP_NODELAY);

 serverSocketOptions = Set.of(StandardSocketOptions.SO_RCVBUF,
 StandardSocketOptions.SO_REUSEADDR,
 StandardSocketOptions.IP_TOS);
 }

 /**
 * Returns a set of SocketOptions supported by this impl
 * and by this impl's socket (Socket or ServerSocket)
 *
 * @return a Set of SocketOptions
 *
 * @since 9
 */
 protected Set<SocketOption<?>> supportedOptions() {
 if (getSocket() != null) {
 return socketOptions;
 } else {
 return serverSocketOptions;
 }
 }
}