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 * Copyright (c) 2019, 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 jdk.dns.client.internal;

import jdk.dns.client.ex.DnsResolverException;

import java.util.Vector;

/**

 * The ResourceRecords class represents the resource records in the

 * four sections of a DNS message.

 * <p>

 * The additional records section is currently ignored.

 *

 * @author Scott Seligman

 */

public class ResourceRecords {

    // Four sections:  question, answer, authority, additional.

    // The question section is treated as being made up of (shortened)

    // resource records, although this isn't technically how it's defined.

    Vector<ResourceRecord> question = new Vector<>();

    public Vector<ResourceRecord> answer = new Vector<>();

    Vector<ResourceRecord> authority = new Vector<>();

    // TODO: Try to reuse additional section to avoid additional CNAME lookups

    public Vector<ResourceRecord> additional = new Vector<>();

    public boolean hasAddressOrAlias() {

        return answer.stream().anyMatch(

                rr -> rr.rrtype == ResourceRecord.TYPE_A

                        || rr.rrtype == ResourceRecord.TYPE_AAAA

                        || rr.rrtype == ResourceRecord.TYPE_CNAME);

    }

    /*

     * True if these resource records are from a zone transfer.  In

     * that case only answer records are read (as per

     * draft-ietf-dnsext-axfr-clarify-02.txt).  Also, the rdata of

     * those answer records is not decoded (for efficiency) except

     * for SOA records.

     */

    boolean zoneXfer;

    /*

     * Returns a representation of the resource records in a DNS message.

     * Does not modify or store a reference to the msg array.

     */

    ResourceRecords(byte[] msg, int msgLen, Header hdr, boolean zoneXfer)

            throws DnsResolverException {

        if (zoneXfer) {

            answer.ensureCapacity(8192);        // an arbitrary "large" number

        }

        this.zoneXfer = zoneXfer;

        add(msg, msgLen, hdr);

    }

    /*

     * Returns the type field of the first answer record, or -1 if

     * there are no answer records.

     */

    int getFirstAnsType() {

        if (answer.size() == 0) {

            return -1;

        }

        return answer.firstElement().getType();

    }

    /*

     * Returns the type field of the last answer record, or -1 if

     * there are no answer records.

     */

    int getLastAnsType() {

        if (answer.size() == 0) {

            return -1;

        }

        return answer.lastElement().getType();

    }

    /*

     * Decodes the resource records in a DNS message and adds

     * them to this object.

     * Does not modify or store a reference to the msg array.

     */

    void add(byte[] msg, int msgLen, Header hdr) throws DnsResolverException {

        ResourceRecord rr;

        int pos = Header.HEADER_SIZE;   // current offset into msg

        try {

            for (int i = 0; i < hdr.numQuestions; i++) {

                rr = new ResourceRecord(msg, msgLen, pos, true, false);

                if (!zoneXfer) {

                    question.addElement(rr);

                }

                pos += rr.size();

            }

            for (int i = 0; i < hdr.numAnswers; i++) {

                rr = new ResourceRecord(

                        msg, msgLen, pos, false, !zoneXfer);

                answer.addElement(rr);

                pos += rr.size();

            }

            if (zoneXfer) {

                return;

            }

            for (int i = 0; i < hdr.numAuthorities; i++) {

                rr = new ResourceRecord(msg, msgLen, pos, false, true);

                authority.addElement(rr);

                pos += rr.size();

            }

            // TODO: Might be useful

            // The additional records section is currently ignored.

//            for (int i = 0; i < hdr.numAdditionals; i++) {

//                rr = new ResourceRecord(msg, msgLen, pos, false, true);

//                additional.addElement(rr);

//                pos += rr.size();

//            }

        } catch (IndexOutOfBoundsException e) {

            throw new DnsResolverException(

                    "DNS error: corrupted message");

        }

    }

}