Add a method to ObjectInserter to read back inserted objects

In the DFS implementation, flushing an inserter writes a new pack to
the storage system and is potentially very slow, but was the only way
to ensure previously-inserted objects were available.  For some tasks,
like performing a series of three-way merges, the total size of all
inserted objects may be small enough to avoid flushing the in-memory
buffered data.

DfsOutputStream already provides a read method to read back from the
not-yet-flushed data, so use this to provide an ObjectReader in the
DFS case.

In the file-backed case, objects are written out loosely on the fly,
so the implementation can just return the existing WindowCursor.

Change-Id: I454fdfb88f4d215e31b7da2b2a069853b197b3dd

1 files changed, 175 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsInserterTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsInserterTest.java
new file mode 100644
index 0000000000..693388c0bf
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsInserterTest.java
@@ -0,0 +1,175 @@
+/*
+ * Copyright (C) 2013, 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.internal.storage.dfs;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.zip.Deflater;
+
+import org.eclipse.jgit.internal.storage.pack.PackExt;
+import org.eclipse.jgit.junit.JGitTestUtil;
+import org.eclipse.jgit.junit.TestRng;
+import org.eclipse.jgit.lib.AbbreviatedObjectId;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectInserter;
+import org.eclipse.jgit.lib.ObjectLoader;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.util.IO;
+import org.eclipse.jgit.util.RawParseUtils;
+import org.junit.Before;
+import org.junit.Test;
+
+public class DfsInserterTest {
+	InMemoryRepository db;
+
+	@Before
+	public void setUp() {
+		db = new InMemoryRepository(new DfsRepositoryDescription("test"));
+	}
+
+	@Test
+	public void testInserterDiscardsPack() throws IOException {
+		ObjectInserter ins = db.newObjectInserter();
+		ins.insert(Constants.OBJ_BLOB, Constants.encode("foo"));
+		ins.insert(Constants.OBJ_BLOB, Constants.encode("bar"));
+		assertEquals(0, db.getObjectDatabase().listPacks().size());
+
+		ins.release();
+		assertEquals(0, db.getObjectDatabase().listPacks().size());
+	}
+
+	@Test
+	public void testReadFromInserterSmallObjects() throws IOException {
+		ObjectInserter ins = db.newObjectInserter();
+		ObjectId id1 = ins.insert(Constants.OBJ_BLOB, Constants.encode("foo"));
+		ObjectId id2 = ins.insert(Constants.OBJ_BLOB, Constants.encode("bar"));
+		assertEquals(0, db.getObjectDatabase().listPacks().size());
+
+		ObjectReader reader = ins.newReader();
+		assertEquals("foo", readString(reader.open(id1)));
+		assertEquals("bar", readString(reader.open(id2)));
+		assertEquals(0, db.getObjectDatabase().listPacks().size());
+		ins.flush();
+		assertEquals(1, db.getObjectDatabase().listPacks().size());
+	}
+
+	@Test
+	public void testReadFromInserterLargerObjects() throws IOException {
+		db.getObjectDatabase().getReaderOptions().setStreamFileThreshold(512);
+		DfsBlockCache.reconfigure(new DfsBlockCacheConfig()
+			.setBlockSize(512)
+			.setBlockLimit(2048));
+
+		byte[] data = new TestRng(JGitTestUtil.getName()).nextBytes(8192);
+		DfsInserter ins = (DfsInserter) db.newObjectInserter();
+		ins.setCompressionLevel(Deflater.NO_COMPRESSION);
+		ObjectId id1 = ins.insert(Constants.OBJ_BLOB, data);
+		assertEquals(0, db.getObjectDatabase().listPacks().size());
+
+		ObjectReader reader = ins.newReader();
+		assertTrue(Arrays.equals(data, readStream(reader.open(id1))));
+		assertEquals(0, db.getObjectDatabase().listPacks().size());
+		ins.flush();
+
+		List<DfsPackDescription> packs = db.getObjectDatabase().listPacks();
+		assertEquals(1, packs.size());
+		assertTrue(packs.get(0).getFileSize(PackExt.PACK) > 2048);
+	}
+
+	@Test
+	public void testReadFromFallback() throws IOException {
+		ObjectInserter ins = db.newObjectInserter();
+		ObjectId id1 = ins.insert(Constants.OBJ_BLOB, Constants.encode("foo"));
+		ins.flush();
+		ObjectId id2 = ins.insert(Constants.OBJ_BLOB, Constants.encode("bar"));
+		assertEquals(1, db.getObjectDatabase().listPacks().size());
+
+		ObjectReader reader = ins.newReader();
+		assertEquals("foo", readString(reader.open(id1)));
+		assertEquals("bar", readString(reader.open(id2)));
+		assertEquals(1, db.getObjectDatabase().listPacks().size());
+		ins.flush();
+		assertEquals(2, db.getObjectDatabase().listPacks().size());
+	}
+
+	@Test
+	public void testReaderResolve() throws IOException {
+		ObjectInserter ins = db.newObjectInserter();
+		ObjectId id1 = ins.insert(Constants.OBJ_BLOB, Constants.encode("foo"));
+		ins.flush();
+		ObjectId id2 = ins.insert(Constants.OBJ_BLOB, Constants.encode("bar"));
+		String abbr1 = ObjectId.toString(id1).substring(0, 4);
+		String abbr2 = ObjectId.toString(id2).substring(0, 4);
+		assertFalse(abbr1.equals(abbr2));
+
+		ObjectReader reader = ins.newReader();
+		Collection<ObjectId> objs;
+		objs = reader.resolve(AbbreviatedObjectId.fromString(abbr1));
+		assertEquals(1, objs.size());
+		assertEquals(id1, objs.iterator().next());
+
+		objs = reader.resolve(AbbreviatedObjectId.fromString(abbr2));
+		assertEquals(1, objs.size());
+		assertEquals(id2, objs.iterator().next());
+	}
+
+	private static String readString(ObjectLoader loader) throws IOException {
+		return RawParseUtils.decode(readStream(loader));
+	}
+
+	private static byte[] readStream(ObjectLoader loader) throws IOException {
+		ByteBuffer bb = IO.readWholeStream(loader.openStream(), 64);
+		byte[] buf = new byte[bb.remaining()];
+		bb.get(buf);
+		return buf;
+	}
+}