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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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,
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package com.sun.jndi.ldap.pool;

import java.util.concurrent.locks.ReentrantLock;

/**
 * Represents a description of PooledConnection in Connections.
 * Contains a PooledConnection, its state (busy, idle, expired), and idle time.
 *
 * Any access or update to a descriptor's state is synchronized.
 *
 * @author Rosanna Lee
 */
final class ConnectionDesc {
    private static final boolean debug = Pool.debug;

    // Package private because used by Pool.showStats()
    static final byte BUSY = (byte)0;
    static final byte IDLE = (byte)1;
    static final byte EXPIRED = (byte)2;

    private final PooledConnection conn;

    private byte state = IDLE;  // initial state
    private long idleSince;
    private long useCount = 0;  // for stats & debugging only
    // ConnectionDesc instance lock
    private final ReentrantLock lock = new ReentrantLock();

    ConnectionDesc(PooledConnection conn) {
        this.conn = conn;
    }

    ConnectionDesc(PooledConnection conn, boolean use) {
        this.conn = conn;
        if (use) {
            state = BUSY;
            ++useCount;
        }
    }

    /**
     * Two desc are equal if their PooledConnections are the same.
     * This is useful when searching for a ConnectionDesc using only its
     * PooledConnection.
     */
    public boolean equals(Object obj) {
        return (obj instanceof ConnectionDesc other)
            && other.conn == conn;
    }

    /**
     * Hashcode is that of PooledConnection to facilitate
     * searching for a ConnectionDesc using only its PooledConnection.
     */
    public int hashCode() {
        return conn.hashCode();
    }

    /**
     * Changes the state of a ConnectionDesc from BUSY to IDLE and
     * records the current time so that we will know how long it has been idle.
     * @return true if state change occurred.
     */
    boolean release() {
        lock.lock();
        try {
            d("release()");
            if (state == BUSY) {
                state = IDLE;

                idleSince = System.currentTimeMillis();
                return true;  // Connection released, ready for reuse
            } else {
                return false; // Connection wasn't busy to begin with
            }
        } finally {
            lock.unlock();
        }
    }

    /**
     * If ConnectionDesc is IDLE, change its state to BUSY and return
     * its connection.
     *
     * @return ConnectionDesc's PooledConnection if it was idle; null otherwise.
     */
    PooledConnection tryUse() {
        lock.lock();
        try {
            d("tryUse()");

            if (state == IDLE) {
                state = BUSY;
                ++useCount;
                return conn;
            }

            return null;
        } finally {
            lock.unlock();
        }
    }

    /**
     * If ConnectionDesc is IDLE and has expired, close the corresponding
     * PooledConnection.
     *
     * @param threshold a connection that has been idle before this time
     *     have expired.
     *
     * @return true if entry is idle and has expired; false otherwise.
     */
    boolean expire(long threshold) {
        lock.lock();
        try {
            if (state == IDLE && idleSince < threshold) {

                d("expire(): expired");

                state = EXPIRED;
                conn.closeConnection();  // Close real connection

                return true;  // Expiration successful
            } else {
                d("expire(): not expired");
                return false; // Expiration did not occur
            }
        } finally {
            lock.unlock();
        }
    }

    public String toString() {
        return conn.toString() + " " +
            (state == BUSY ? "busy" : (state == IDLE ? "idle" : "expired"));
    }

    // Used by Pool.showStats()
    int getState() {
        return state;
    }

    // Used by Pool.showStats()
    long getUseCount() {
        return useCount;
    }

    private void d(String msg) {
        if (debug) {
            System.err.println("ConnectionDesc." + msg + " " + toString());
        }
    }
}