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 * 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 com.sun.jndi.dns;

import java.lang.ref.SoftReference;

import java.util.Date;

import java.util.Vector;

/**

 * ZoneNode extends NameNode to represent a tree of the zones in the

 * DNS namespace, along with any intermediate nodes between zones.

 * A ZoneNode that represents a zone may be "populated" with a

 * NameNode tree containing the zone's contents.

 *

 * <p> A populated zone's contents will be flagged as having expired after

 * the time specified by the minimum TTL value in the zone's SOA record.

 *

 * <p> Since zone cuts aren't directly modeled by a tree of ZoneNodes,

 * ZoneNode.isZoneCut() always returns false.

 *

 * <p> The synchronization strategy is documented in DnsContext.java.

 *

 * <p> The zone's contents are accessed via a soft reference, so its

 * heap space may be reclaimed when necessary.  The zone may be

 * repopulated later.

 *

 * @author Scott Seligman

 */

class ZoneNode extends NameNode {

    private SoftReference<NameNode> contentsRef = null;   // the zone's namespace

    private long serialNumber = -1;     // the zone data's serial number

    private Date expiration = null;     // time when the zone's data expires

    ZoneNode(String label) {

        super(label);

    }

    protected NameNode newNameNode(String label) {

        return new ZoneNode(label);

    }

    /*

     * Clears the contents of this node.  If the node was flagged as

     * expired, it remains so.

     */

    synchronized void depopulate() {

        contentsRef = null;

        serialNumber = -1;

    }

    /*

     * Is this node currently populated?

     */

    synchronized boolean isPopulated() {

        return (getContents() != null);

    }

    /*

     * Returns the zone's contents, or null if the zone is not populated.

     */

    synchronized NameNode getContents() {

        return (contentsRef != null)

                ? contentsRef.get()

                : null;

    }

    /*

     * Has this zone's data expired?

     */

    synchronized boolean isExpired() {

        return ((expiration != null) && expiration.before(new Date()));

    }

    /*

     * Returns the deepest populated zone on the path specified by a

     * fully-qualified domain name, or null if there is no populated

     * zone on that path.  Note that a node may be depopulated after

     * being returned.

     */

    ZoneNode getDeepestPopulated(DnsName fqdn) {

        ZoneNode znode = this;

        ZoneNode popNode = isPopulated() ? this : null;

        for (int i = 1; i < fqdn.size(); i++) { //     "i=1" to skip root label

            znode = (ZoneNode) znode.get(fqdn.getKey(i));

            if (znode == null) {

                break;

            } else if (znode.isPopulated()) {

                popNode = znode;

            }

        }

        return popNode;

    }

    /*

     * Populates (or repopulates) a zone given its own fully-qualified

     * name and its resource records.  Returns the zone's new contents.

     */

    NameNode populate(DnsName zone, ResourceRecords rrs) {

        // assert zone.get(0).isEmpty();               // zone has root label

        // assert (zone.size() == (depth() + 1));       // +1 due to root label

        NameNode newContents = new NameNode(null);

        for (int i = 0; i < rrs.answer.size(); i++) {

            ResourceRecord rr = rrs.answer.elementAt(i);

            DnsName n = rr.getName();

            // Ignore resource records whose names aren't within the zone's

            // domain.  Also skip records of the zone's top node, since

            // the zone's root NameNode is already in place.

            if ((n.size() > zone.size()) && n.startsWith(zone)) {

                NameNode nnode = newContents.add(n, zone.size());

                if (rr.getType() == ResourceRecord.TYPE_NS) {

                    nnode.setZoneCut(true);

                }

            }

        }

        // The zone's SOA record is the first record in the answer section.

        ResourceRecord soa = rrs.answer.firstElement();

        synchronized (this) {

            contentsRef = new SoftReference<NameNode>(newContents);

            serialNumber = getSerialNumber(soa);

            setExpiration(getMinimumTtl(soa));

            return newContents;

        }

    }

    /*

     * Set this zone's data to expire in {@code secsToExpiration} seconds.

     */

    private void setExpiration(long secsToExpiration) {

        expiration = new Date(System.currentTimeMillis() +

                              1000 * secsToExpiration);

    }

    /*

     * Returns an SOA record's minimum TTL field.

     */

    private static long getMinimumTtl(ResourceRecord soa) {

        String rdata = (String) soa.getRdata();

        int pos = rdata.lastIndexOf(' ') + 1;

        return Long.parseLong(rdata.substring(pos));

    }

    /*

     * Compares this zone's serial number with that of an SOA record.

     * Zone must be populated.

     * Returns a negative, zero, or positive integer as this zone's

     * serial number is less than, equal to, or greater than the SOA

     * record's.

     * See ResourceRecord.compareSerialNumbers() for a description of

     * serial number arithmetic.

     */

    int compareSerialNumberTo(ResourceRecord soa) {

        // assert isPopulated();

        return ResourceRecord.compareSerialNumbers(serialNumber,

                                                   getSerialNumber(soa));

    }

    /*

     * Returns an SOA record's serial number.

     */

    private static long getSerialNumber(ResourceRecord soa) {

        String rdata = (String) soa.getRdata();

        // An SOA record ends with:  serial refresh retry expire minimum.

        // Set "beg" to the space before serial, and "end" to the space after.

        // We go "backward" to avoid dealing with escaped spaces in names.

        int beg = rdata.length();

        int end = -1;

        for (int i = 0; i < 5; i++) {

            end = beg;

            beg = rdata.lastIndexOf(' ', end - 1);

        }

        return Long.parseLong(rdata.substring(beg + 1, end));

    }

}