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// Copyright (c) 1999-2004 Brian Wellington (bwelling@xbill.org)
package org.xbill.DNS;
/**
* DNS Name Compression object.
* @see Message
* @see Name
*
* @author Brian Wellington
*/
public class Compression {
private static class Entry {
Name name;
int pos;
Entry next;
}
private static final int TABLE_SIZE = 17;
private static final int MAX_POINTER = 0x3FFF;
private Entry [] table;
private boolean verbose = Options.check("verbosecompression");
/**
* Creates a new Compression object.
*/
public
Compression() {
table = new Entry[TABLE_SIZE];
}
/**
* Adds a compression entry mapping a name to a position in a message.
* @param pos The position at which the name is added.
* @param name The name being added to the message.
*/
public void
add(int pos, Name name) {
if (pos > MAX_POINTER)
return;
int row = (name.hashCode() & 0x7FFFFFFF) % TABLE_SIZE;
Entry entry = new Entry();
entry.name = name;
entry.pos = pos;
entry.next = table[row];
table[row] = entry;
if (verbose)
System.err.println("Adding " + name + " at " + pos);
}
/**
* Retrieves the position of the given name, if it has been previously
* included in the message.
* @param name The name to find in the compression table.
* @return The position of the name, or -1 if not found.
*/
public int
get(Name name) {
int row = (name.hashCode() & 0x7FFFFFFF) % TABLE_SIZE;
int pos = -1;
for (Entry entry = table[row]; entry != null; entry = entry.next) {
if (entry.name.equals(name))
pos = entry.pos;
}
if (verbose)
System.err.println("Looking for " + name + ", found " + pos);
return pos;
}
}
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