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package com.sun.jndi.dns;


import java.util.Vector;
import javax.naming.*;


The ResourceRecords class represents the resource records in the four sections of a DNS message. The additional records section is currently ignored.
Author:Scott Seligman
/** * The ResourceRecords class represents the resource records in the * four sections of a DNS message. * * The additional records section is currently ignored. * * @author Scott Seligman */
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 question = new Vector(); Vector answer = new Vector(); Vector authority = new Vector(); Vector additional = new Vector(); /* * 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 NamingException { 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 ((ResourceRecord) 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 ((ResourceRecord) 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 NamingException { 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(); } // The additional records section is currently ignored. } catch (IndexOutOfBoundsException e) { throw new CommunicationException( "DNS error: corrupted message"); } } }