--- a/src/com/tmate/hgkit/ll/HgDataFile.java	Mon Dec 27 01:00:53 2010 +0100
+++ b/src/com/tmate/hgkit/ll/HgDataFile.java	Mon Dec 27 01:43:08 2010 +0100
@@ -1,10 +1,12 @@
-/**
+/*
  * Copyright (c) 2010 Artem Tikhomirov 
  */
 package com.tmate.hgkit.ll;
 
 import static com.tmate.hgkit.ll.HgRepository.TIP;
 
+import java.util.Arrays;
+
 /**
  * Extends Revlog/uses RevlogStream?
  * ? name:HgFileNode?
@@ -71,4 +73,61 @@
 	public void history(int start, int end, Changeset.Inspector i) {
 		throw HgRepository.notImplemented();
 	}
+
+	/**
+	 * XXX perhaps, return value Nodeid[2] and boolean needNodeids is better (and higher level) API for this query?
+	 * 
+	 * @param revision - revision to query parents, or {@link HgRepository#TIP}
+	 * @param parentRevisions - int[2] to get local revision numbers of parents (e.g. {6, -1})
+	 * @param parent1 - byte[20] or null, if parent's nodeid is not needed
+	 * @param parent2 - byte[20] or null, if second parent's nodeid is not needed
+	 * @return
+	 */
+	public void parents(int revision, int[] parentRevisions, byte[] parent1, byte[] parent2) {
+		if (revision != TIP && !(revision >= 0 && revision < content.revisionCount())) {
+			throw new IllegalArgumentException(String.valueOf(revision));
+		}
+		if (parentRevisions == null || parentRevisions.length < 2) {
+			throw new IllegalArgumentException(String.valueOf(parentRevisions));
+		}
+		if (parent1 != null && parent1.length < 20) {
+			throw new IllegalArgumentException(parent1.toString());
+		}
+		if (parent2 != null && parent2.length < 20) {
+			throw new IllegalArgumentException(parent2.toString());
+		}
+		class ParentCollector implements Revlog.Inspector {
+			public int p1 = -1;
+			public int p2 = -1;
+			public byte[] nodeid;
+			
+			public void next(int revisionNumber, int actualLen, int baseRevision, int linkRevision, int parent1Revision, int parent2Revision, byte[] nodeid, byte[] data) {
+				p1 = parent1Revision;
+				p2 = parent2Revision;
+				this.nodeid = new byte[20];
+				// nodeid arg now comes in 32 byte from (as in file format description), however upper 12 bytes are zeros.
+				System.arraycopy(nodeid, nodeid.length > 20 ? nodeid.length - 20 : 0, this.nodeid, 0, 20);
+			}
+		};
+		ParentCollector pc = new ParentCollector();
+		content.iterate(revision, revision, false, pc);
+		parentRevisions[0] = pc.p1;
+		parentRevisions[1] = pc.p2;
+		if (parent1 != null) {
+			if (parentRevisions[0] == -1) {
+				Arrays.fill(parent1, 0, 20, (byte) 0);
+			} else {
+				content.iterate(parentRevisions[0], parentRevisions[0], false, pc);
+				System.arraycopy(pc.nodeid, 0, parent1, 0, 20);
+			}
+		}
+		if (parent2 != null) {
+			if (parentRevisions[1] == -1) {
+				Arrays.fill(parent2, 0, 20, (byte) 0);
+			} else {
+				content.iterate(parentRevisions[1], parentRevisions[1], false, pc);
+				System.arraycopy(pc.nodeid, 0, parent2, 0, 20);
+			}
+		}
+	}
 }