--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/internal/RevlogDelegate.java	Mon Aug 05 18:45:16 2013 +0200
@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2013 TMate Software Ltd
+ *  
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program 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 for more details.
+ *
+ * For information on how to redistribute this software under
+ * the terms of a license other than GNU General Public License
+ * contact TMate Software at support@hg4j.com
+ */
+package org.tmatesoft.hg.internal;
+
+import org.tmatesoft.hg.core.Nodeid;
+import org.tmatesoft.hg.internal.RevlogStream.Inspector;
+import org.tmatesoft.hg.repo.HgRepository;
+import org.tmatesoft.hg.repo.HgRuntimeException;
+
+/**
+ * Does almost nothing, facilitates chains of inspectors and sharing certain information between them 
+ * 
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+public abstract class RevlogDelegate implements RevlogStream.Inspector {
+	
+	private final Inspector next;
+	private Nodeid nid;
+	private final RevlogDelegate nextAsRD;
+	
+	protected RevlogDelegate(RevlogStream.Inspector nextInChain) {
+		next = nextInChain;
+		if (nextInChain instanceof RevlogDelegate) {
+			// additional benefits
+			nextAsRD = (RevlogDelegate) nextInChain;
+		} else {
+			nextAsRD = null;
+		}
+	}
+
+	/**
+	 * iterates index only and ensures pre/post processing is invoked for the chain
+	 */
+	public void walk(HgRepository hgRepo, RevlogStream stream, int from, int to) {
+		// hgRepo is handy for present uses, but is generally not appropriate, 
+		// it's ok to refactor and let subclasses get what they need through e.g. a cons 
+		stream.iterate(from, to, false, this);
+		postWalk(hgRepo);
+	}
+	
+	// does nothing but gives a chance to delegate to handle the same
+	protected void postWalk(HgRepository hgRepo) {
+		if (nextAsRD != null) {
+			nextAsRD.postWalk(hgRepo);
+		}
+	}
+
+	/**
+	 * @return Nodeid of current revision if already known, or a new instance otherwise. 
+	 * The value will propagate to subsequent {@link RevlogDelegate RevlogDelegates}, if any
+	 */
+	protected Nodeid getRevision(byte[] nodeid) {
+		if (nid == null) {
+			nid = Nodeid.fromBinary(nodeid, 0);
+		}
+		return nid;
+	}
+	
+	protected void setRevision(Nodeid nodeid) {
+		nid = nodeid;
+	}
+	
+	public void next(int revisionIndex, int actualLen, int baseRevision, int linkRevision, int parent1Revision, int parent2Revision, byte[] nodeid, DataAccess data) throws HgRuntimeException {
+		if (next != null) {
+			if (nextAsRD != null) {
+				nextAsRD.setRevision(nid); // null is fine
+			}
+			next.next(revisionIndex, actualLen, baseRevision, linkRevision, parent1Revision, parent2Revision, nodeid, data);
+		}
+		nid = null; // forget it, get ready for the next iteration
+	}
+}