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	/*
	* Copyright (c) 1996, 2011, 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
	* questions.
	*/

	package sun.net.www.http;

	import java.io.IOException;
	import java.io.NotSerializableException;
	import java.util.ArrayList;
	import java.util.HashMap;
	import java.net.URL;

	/**
	* A class that implements a cache of idle Http connections for keep-alive
	*
	* @author Stephen R. Pietrowicz (NCSA)
	* @author Dave Brown
	*/
	public class KeepAliveCache
	extends HashMap<KeepAliveKey, ClientVector>
	implements Runnable {
	private static final long serialVersionUID = -2937172892064557949L;

	/* maximum # keep-alive connections to maintain at once
	* This should be 2 by the HTTP spec, but because we don't support pipe-lining
	* a larger value is more appropriate. So we now set a default of 5, and the value
	* refers to the number of idle connections per destination (in the cache) only.
	* It can be reset by setting system property "http.maxConnections".
	*/
	static final int MAX_CONNECTIONS = 5;
	static int result = -1;
	static int getMaxConnections() {
	if (result == -1) {
	result = java.security.AccessController.doPrivileged(
	new sun.security.action.GetIntegerAction("http.maxConnections",
	MAX_CONNECTIONS))
	.intValue();
	if (result <= 0)
	result = MAX_CONNECTIONS;
	}
	return result;
	}

	static final int LIFETIME = 5000;

	private Thread keepAliveTimer = null;

	/**
	* Constructor
	*/
	public KeepAliveCache() {}

	/**
	* Register this URL and HttpClient (that supports keep-alive) with the cache
	* @param url The URL contains info about the host and port
	* @param http The HttpClient to be cached
	*/
	public synchronized void put(final URL url, Object obj, HttpClient http) {
	boolean startThread = (keepAliveTimer == null);
	if (!startThread) {
	if (!keepAliveTimer.isAlive()) {
	startThread = true;
	}
	}
	if (startThread) {
	clear();
	/* Unfortunately, we can't always believe the keep-alive timeout we got
	* back from the server. If I'm connected through a Netscape proxy
	* to a server that sent me a keep-alive
	* time of 15 sec, the proxy unilaterally terminates my connection
	* The robustness to get around this is in HttpClient.parseHTTP()
	*/
	final KeepAliveCache cache = this;
	java.security.AccessController.doPrivileged(
	new java.security.PrivilegedAction<Void>() {
	public Void run() {
	// We want to create the Keep-Alive-Timer in the
	// system threadgroup
	ThreadGroup grp = Thread.currentThread().getThreadGroup();
	ThreadGroup parent = null;
	while ((parent = grp.getParent()) != null) {
	grp = parent;
	}

	keepAliveTimer = new Thread(grp, cache, "Keep-Alive-Timer");
	keepAliveTimer.setDaemon(true);
	keepAliveTimer.setPriority(Thread.MAX_PRIORITY - 2);
	// Set the context class loader to null in order to avoid
	// keeping a strong reference to an application classloader.
	keepAliveTimer.setContextClassLoader(null);
	keepAliveTimer.start();
	return null;
	}
	});
	}

	KeepAliveKey key = new KeepAliveKey(url, obj);
	ClientVector v = super.get(key);

	if (v == null) {
	int keepAliveTimeout = http.getKeepAliveTimeout();
	v = new ClientVector(keepAliveTimeout > 0?
	keepAliveTimeout*1000 : LIFETIME);
	v.put(http);
	super.put(key, v);
	} else {
	v.put(http);
	}
	}

	/* remove an obsolete HttpClient from its VectorCache */
	public synchronized void remove (HttpClient h, Object obj) {
	KeepAliveKey key = new KeepAliveKey(h.url, obj);
	ClientVector v = super.get(key);
	if (v != null) {
	v.remove(h);
	if (v.empty()) {
	removeVector(key);
	}
	}
	}

	/* called by a clientVector thread when all its connections have timed out
	* and that vector of connections should be removed.
	*/
	synchronized void removeVector(KeepAliveKey k) {
	super.remove(k);
	}

	/**
	* Check to see if this URL has a cached HttpClient
	*/
	public synchronized HttpClient get(URL url, Object obj) {

	KeepAliveKey key = new KeepAliveKey(url, obj);
	ClientVector v = super.get(key);
	if (v == null) { // nothing in cache yet
	return null;
	}
	return v.get();
	}

	/* Sleeps for an alloted timeout, then checks for timed out connections.
	* Errs on the side of caution (leave connections idle for a relatively
	* short time).
	*/
	@Override
	public void run() {
	do {
	try {
	Thread.sleep(LIFETIME);
	} catch (InterruptedException e) {}
	synchronized (this) {
	/* Remove all unused HttpClients. Starting from the
	* bottom of the stack (the least-recently used first).
	* REMIND: It'd be nice to not remove all connections
	* that aren't presently in use. One could have been added
	* a second ago that's still perfectly valid, and we're
	* needlessly axing it. But it's not clear how to do this
	* cleanly, and doing it right may be more trouble than it's
	* worth.
	*/

	long currentTime = System.currentTimeMillis();

	ArrayList<KeepAliveKey> keysToRemove
	= new ArrayList<KeepAliveKey>();

	for (KeepAliveKey key : keySet()) {
	ClientVector v = get(key);
	synchronized (v) {
	int i;

	for (i = 0; i < v.size(); i++) {
	KeepAliveEntry e = v.elementAt(i);
	if ((currentTime - e.idleStartTime) > v.nap) {
	HttpClient h = e.hc;
	h.closeServer();
	} else {
	break;
	}
	}
	v.subList(0, i).clear();

	if (v.size() == 0) {
	keysToRemove.add(key);
	}
	}
	}

	for (KeepAliveKey key : keysToRemove) {
	removeVector(key);
	}
	}
	} while (size() > 0);

	return;
	}

	/*
	* Do not serialize this class!
	*/
	private void writeObject(java.io.ObjectOutputStream stream)
	throws IOException {
	throw new NotSerializableException();
	}

	private void readObject(java.io.ObjectInputStream stream)
	throws IOException, ClassNotFoundException {
	throw new NotSerializableException();
	}
	}

	/* FILO order for recycling HttpClients, should run in a thread
	* to time them out. If > maxConns are in use, block.
	*/


	class ClientVector extends java.util.Stack<KeepAliveEntry> {
	private static final long serialVersionUID = -8680532108106489459L;

	// sleep time in milliseconds, before cache clear
	int nap;



	ClientVector (int nap) {
	this.nap = nap;
	}

	synchronized HttpClient get() {
	if (empty()) {
	return null;
	} else {
	// Loop until we find a connection that has not timed out
	HttpClient hc = null;
	long currentTime = System.currentTimeMillis();
	do {
	KeepAliveEntry e = pop();
	if ((currentTime - e.idleStartTime) > nap) {
	e.hc.closeServer();
	} else {
	hc = e.hc;
	}
	} while ((hc== null) && (!empty()));
	return hc;
	}
	}

	/* return a still valid, unused HttpClient */
	synchronized void put(HttpClient h) {
	if (size() >= KeepAliveCache.getMaxConnections()) {
	h.closeServer(); // otherwise the connection remains in limbo
	} else {
	push(new KeepAliveEntry(h, System.currentTimeMillis()));
	}
	}

	/*
	* Do not serialize this class!
	*/
	private void writeObject(java.io.ObjectOutputStream stream)
	throws IOException {
	throw new NotSerializableException();
	}

	private void readObject(java.io.ObjectInputStream stream)
	throws IOException, ClassNotFoundException {
	throw new NotSerializableException();
	}
	}


	class KeepAliveKey {
	private String protocol = null;
	private String host = null;
	private int port = 0;
	private Object obj = null; // additional key, such as socketfactory

	/**
	* Constructor
	*
	* @param url the URL containing the protocol, host and port information
	*/
	public KeepAliveKey(URL url, Object obj) {
	this.protocol = url.getProtocol();
	this.host = url.getHost();
	this.port = url.getPort();
	this.obj = obj;
	}

	/**
	* Determine whether or not two objects of this type are equal
	*/
	@Override
	public boolean equals(Object obj) {
	if ((obj instanceof KeepAliveKey) == false)
	return false;
	KeepAliveKey kae = (KeepAliveKey)obj;
	return host.equals(kae.host)
	&& (port == kae.port)
	&& protocol.equals(kae.protocol)
	&& this.obj == kae.obj;
	}

	/**
	* The hashCode() for this object is the string hashCode() of
	* concatenation of the protocol, host name and port.
	*/
	@Override
	public int hashCode() {
	String str = protocol+host+port;
	return this.obj == null? str.hashCode() :
	str.hashCode() + this.obj.hashCode();
	}
	}

	class KeepAliveEntry {
	HttpClient hc;
	long idleStartTime;

	KeepAliveEntry(HttpClient hc, long idleStartTime) {
	this.hc = hc;
	this.idleStartTime = idleStartTime;
	}
	}

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