/*
 * Copyright (c) 2005, 2020, 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
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package sun.net.www.http;

import java.io.IOException;
import java.util.LinkedList;
import sun.net.NetProperties;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

This class is used to cleanup any remaining data that may be on a KeepAliveStream
so that the connection can be cached in the KeepAliveCache.
Instances of this class can be used as a FIFO queue for KeepAliveCleanerEntry objects.
Executing this Runnable removes each KeepAliveCleanerEntry from the Queue, reads
the reamining bytes on its KeepAliveStream, and if successful puts the connection in
the KeepAliveCache.
Author:
Chris Hegarty/**
 * This class is used to cleanup any remaining data that may be on a KeepAliveStream
 * so that the connection can be cached in the KeepAliveCache.
 * Instances of this class can be used as a FIFO queue for KeepAliveCleanerEntry objects.
 * Executing this Runnable removes each KeepAliveCleanerEntry from the Queue, reads
 * the reamining bytes on its KeepAliveStream, and if successful puts the connection in
 * the KeepAliveCache.
 *
 * @author Chris Hegarty
 */

@SuppressWarnings("serial")  // never serialized
class KeepAliveStreamCleaner
    extends LinkedList<KeepAliveCleanerEntry>
    implements Runnable
{
    // maximum amount of remaining data that we will try to cleanup
    protected static int MAX_DATA_REMAINING = 512;

    // maximum amount of KeepAliveStreams to be queued
    protected static int MAX_CAPACITY = 10;

    // timeout for both socket and poll on the queue
    protected static final int TIMEOUT = 5000;

    // max retries for skipping data
    private static final int MAX_RETRIES = 5;

    static {
        final String maxDataKey = "http.KeepAlive.remainingData";
        int maxData = AccessController.doPrivileged(
            new PrivilegedAction<Integer>() {
                public Integer run() {
                    return NetProperties.getInteger(maxDataKey, MAX_DATA_REMAINING);
                }}).intValue() * 1024;
        MAX_DATA_REMAINING = maxData;

        final String maxCapacityKey = "http.KeepAlive.queuedConnections";
        int maxCapacity = AccessController.doPrivileged(
            new PrivilegedAction<Integer>() {
                public Integer run() {
                    return NetProperties.getInteger(maxCapacityKey, MAX_CAPACITY);
                }}).intValue();
        MAX_CAPACITY = maxCapacity;

    }

    private final ReentrantLock queueLock = new ReentrantLock();
    private final Condition waiter = queueLock.newCondition();

    final void signalAll() {
        waiter.signalAll();
    }

    final void lock() {
        queueLock.lock();
    }

    final void unlock() {
        queueLock.unlock();
    }

    @Override
    public boolean offer(KeepAliveCleanerEntry e) {
        if (size() >= MAX_CAPACITY)
            return false;

        return super.offer(e);
    }

    @Override
    public void run()
    {
        KeepAliveCleanerEntry kace = null;

        do {
            try {
                lock();
                try {
                    long before = System.currentTimeMillis();
                    long timeout = TIMEOUT;
                    while ((kace = poll()) == null) {
                        waiter.await(timeout, TimeUnit.MILLISECONDS);

                        long after = System.currentTimeMillis();
                        long elapsed = after - before;
                        if (elapsed > timeout) {
                            /* one last try */
                            kace = poll();
                            break;
                        }
                        before = after;
                        timeout -= elapsed;
                    }
                } finally {
                    unlock();
                }

                if(kace == null)
                    break;

                KeepAliveStream kas = kace.getKeepAliveStream();

                if (kas != null) {
                    kas.lock();
                    try {
                        HttpClient hc = kace.getHttpClient();
                        try {
                            if (hc != null && !hc.isInKeepAliveCache()) {
                                int oldTimeout = hc.getReadTimeout();
                                hc.setReadTimeout(TIMEOUT);
                                long remainingToRead = kas.remainingToRead();
                                if (remainingToRead > 0) {
                                    long n = 0;
                                    int retries = 0;
                                    while (n < remainingToRead && retries < MAX_RETRIES) {
                                        remainingToRead = remainingToRead - n;
                                        n = kas.skip(remainingToRead);
                                        if (n == 0)
                                            retries++;
                                    }
                                    remainingToRead = remainingToRead - n;
                                }
                                if (remainingToRead == 0) {
                                    hc.setReadTimeout(oldTimeout);
                                    hc.finished();
                                } else
                                    hc.closeServer();
                            }
                        } catch (IOException ioe) {
                            hc.closeServer();
                        } finally {
                            kas.setClosed();
                        }
                    } finally {
                        kas.unlock();
                    }
                }
            } catch (InterruptedException ie) { }
        } while (kace != null);
    }
}