1 files changed, 72 insertions, 0 deletions
diff --git a/src/org/xbill/DNS/Compression.java b/src/org/xbill/DNS/Compression.java
new file mode 100644
index 0000000..e3e81c0
--- /dev/null
+++ b/src/org/xbill/DNS/Compression.java
@@ -0,0 +1,72 @@
+// 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;
+}
+
+}