debug-show-packdelta: Dump a pack delta to the console

This is a horribly crude application, it doesn't even verify that
the object its dumping is delta encoded.  Its method of getting the
delta is pretty abusive to the public PackWriter API, because right
now we don't want to expose the real internal low-level methods
actually required to do this.

Change-Id: I437a17ceb98708b5603a2061126eb251e82f4ed4
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

3 files changed, 129 insertions, 0 deletions

diff --git a/org.eclipse.jgit.pgm/META-INF/MANIFEST.MF b/org.eclipse.jgit.pgm/META-INF/MANIFEST.MF
index 0a4376921a..d6eac232e1 100644
--- a/org.eclipse.jgit.pgm/META-INF/MANIFEST.MF
+++ b/org.eclipse.jgit.pgm/META-INF/MANIFEST.MF
@@ -18,6 +18,7 @@ Import-Package: org.eclipse.jgit.api;version="[0.9.0,0.10.0)",
  org.eclipse.jgit.revwalk;version="[0.9.0,0.10.0)",
  org.eclipse.jgit.revwalk.filter;version="[0.9.0,0.10.0)",
  org.eclipse.jgit.storage.file;version="[0.9.0,0.10.0)",
+ org.eclipse.jgit.storage.pack;version="[0.9.0,0.10.0)",
  org.eclipse.jgit.transport;version="[0.9.0,0.10.0)",
  org.eclipse.jgit.treewalk;version="[0.9.0,0.10.0)",
  org.eclipse.jgit.treewalk.filter;version="[0.9.0,0.10.0)",
diff --git a/org.eclipse.jgit.pgm/META-INF/services/org.eclipse.jgit.pgm.TextBuiltin b/org.eclipse.jgit.pgm/META-INF/services/org.eclipse.jgit.pgm.TextBuiltin
index 0d4a140e62..075cadef79 100644
--- a/org.eclipse.jgit.pgm/META-INF/services/org.eclipse.jgit.pgm.TextBuiltin
+++ b/org.eclipse.jgit.pgm/META-INF/services/org.eclipse.jgit.pgm.TextBuiltin
@@ -30,6 +30,7 @@ org.eclipse.jgit.pgm.debug.RebuildCommitGraph
 org.eclipse.jgit.pgm.debug.ShowCacheTree
 org.eclipse.jgit.pgm.debug.ShowCommands
 org.eclipse.jgit.pgm.debug.ShowDirCache
+org.eclipse.jgit.pgm.debug.ShowPackDelta
 org.eclipse.jgit.pgm.debug.WriteDirCache
 
 org.eclipse.jgit.pgm.eclipse.Iplog
diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/ShowPackDelta.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/ShowPackDelta.java
new file mode 100644
index 0000000000..1718ef30f2
--- /dev/null
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/ShowPackDelta.java
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2010, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.pgm.debug;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.zip.InflaterInputStream;
+
+import org.eclipse.jgit.errors.MissingObjectException;
+import org.eclipse.jgit.errors.StoredObjectRepresentationNotAvailableException;
+import org.eclipse.jgit.lib.NullProgressMonitor;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.pgm.TextBuiltin;
+import org.eclipse.jgit.revwalk.RevObject;
+import org.eclipse.jgit.revwalk.RevWalk;
+import org.eclipse.jgit.storage.pack.BinaryDelta;
+import org.eclipse.jgit.storage.pack.ObjectReuseAsIs;
+import org.eclipse.jgit.storage.pack.ObjectToPack;
+import org.eclipse.jgit.storage.pack.PackOutputStream;
+import org.eclipse.jgit.storage.pack.PackWriter;
+import org.eclipse.jgit.storage.pack.StoredObjectRepresentation;
+import org.eclipse.jgit.util.TemporaryBuffer;
+import org.kohsuke.args4j.Argument;
+
+class ShowPackDelta extends TextBuiltin {
+	@Argument(index = 0)
+	private ObjectId objectId;
+
+	@Override
+	protected void run() throws Exception {
+		ObjectReader reader = db.newObjectReader();
+		RevObject obj = new RevWalk(reader).parseAny(objectId);
+		byte[] delta = getDelta(reader, obj);
+
+		// We're crossing our fingers that this will be a delta. Double
+		// check the size field in the header, it should match.
+		//
+		long size = reader.getObjectSize(obj, obj.getType());
+		try {
+			if (BinaryDelta.getResultSize(delta) != size)
+				throw die("Object " + obj.name() + " is not a delta");
+		} catch (ArrayIndexOutOfBoundsException bad) {
+			throw die("Object " + obj.name() + " is not a delta");
+		}
+
+		out.println(BinaryDelta.format(delta));
+	}
+
+	private byte[] getDelta(ObjectReader reader, RevObject obj)
+			throws IOException, MissingObjectException,
+			StoredObjectRepresentationNotAvailableException {
+		ObjectReuseAsIs asis = (ObjectReuseAsIs) reader;
+		ObjectToPack target = asis.newObjectToPack(obj);
+
+		PackWriter pw = new PackWriter(reader) {
+			@Override
+			public void select(ObjectToPack otp, StoredObjectRepresentation next) {
+				otp.select(next);
+			}
+		};
+
+		ByteArrayOutputStream buf = new ByteArrayOutputStream();
+		asis.selectObjectRepresentation(pw, target);
+		asis.copyObjectAsIs(new PackOutputStream(NullProgressMonitor.INSTANCE,
+				buf, pw), target);
+
+		// At this point the object header has no delta information,
+		// because it was output as though it were a whole object.
+		// Skip over the header and inflate.
+		//
+		byte[] bufArray = buf.toByteArray();
+		int ptr = 0;
+		while ((bufArray[ptr] & 0x80) != 0)
+			ptr++;
+		ptr++;
+
+		TemporaryBuffer.Heap raw = new TemporaryBuffer.Heap(bufArray.length);
+		InflaterInputStream inf = new InflaterInputStream(
+				new ByteArrayInputStream(bufArray, ptr, bufArray.length));
+		raw.copy(inf);
+		inf.close();
+		return raw.toByteArray();
+	}
+}