Fix bug in copyPackBypassCache's skip 'PACK' header logic

Bug caused the pack to be 12 bytes short when cold cache.  Also added
test for copyPackAsIs method.

Change-Id: Idf8fb0e50d1215245d4b032e2e00df4b218c115f
Signed-off-by: Minh Thai <mthai@google.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsPackFileTest.java

@@ -0,0 +1,165 @@
+/*
+ * Copyright (C) 2019, Google LLC.
+ * 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 java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.zip.Deflater;
+
+import org.eclipse.jgit.internal.storage.pack.PackExt;
+import org.eclipse.jgit.internal.storage.pack.PackOutputStream;
+import org.eclipse.jgit.internal.storage.pack.PackWriter;
+import org.eclipse.jgit.junit.JGitTestUtil;
+import org.eclipse.jgit.junit.TestRng;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.NullProgressMonitor;
+import org.junit.Before;
+import org.junit.Test;
+
+public class DfsPackFileTest {
+	InMemoryRepository db;
+	boolean bypassCache;
+	boolean clearCache;
+
+	@Before
+	public void setUp() {
+		db = new InMemoryRepository(new DfsRepositoryDescription("test"));
+	}
+
+	@Test
+	public void testCopyPackBypassCachesSmallCached() throws IOException {
+		bypassCache = true;
+		clearCache = false;
+		setupPack(512, 256);
+		assertPackSize();
+	}
+
+	@Test
+	public void testCopyPackBypassCacheSmallNoCache() throws IOException {
+		bypassCache = true;
+		clearCache = true;
+		setupPack(512, 256);
+		assertPackSize();
+	}
+
+	@Test
+	public void testCopyPackBypassCacheLargeCached() throws IOException {
+		bypassCache = true;
+		clearCache = false;
+		setupPack(512, 8000);
+		assertPackSize();
+	}
+
+	@Test
+	public void testCopyPackBypassCacheLargeNoCache() throws IOException {
+		bypassCache = true;
+		clearCache = true;
+		setupPack(512, 8000);
+		assertPackSize();
+	}
+
+	@Test
+	public void testCopyPackThroughCacheSmallCached() throws IOException {
+		bypassCache = false;
+		clearCache = false;
+		setupPack(512, 256);
+		assertPackSize();
+	}
+
+	@Test
+	public void testCopyPackThroughCacheSmallNoCache() throws IOException {
+		bypassCache = false;
+		clearCache = true;
+		setupPack(512, 256);
+		assertPackSize();
+	}
+
+	@Test
+	public void testCopyPackThroughCacheLargeCached() throws IOException {
+		bypassCache = false;
+		clearCache = false;
+		setupPack(512, 8000);
+		assertPackSize();
+	}
+
+	@Test
+	public void testCopyPackThroughCacheLargeNoCache() throws IOException {
+		bypassCache = false;
+		clearCache = true;
+		setupPack(512, 8000);
+		assertPackSize();
+	}
+
+	private void setupPack(int bs, int ps) throws IOException {
+		DfsBlockCacheConfig cfg = new DfsBlockCacheConfig().setBlockSize(bs)
+				.setBlockLimit(bs * 100).setStreamRatio(bypassCache ? 0F : 1F);
+		DfsBlockCache.reconfigure(cfg);
+
+		byte[] data = new TestRng(JGitTestUtil.getName()).nextBytes(ps);
+		DfsInserter ins = (DfsInserter) db.newObjectInserter();
+		ins.setCompressionLevel(Deflater.NO_COMPRESSION);
+		ins.insert(Constants.OBJ_BLOB, data);
+		ins.flush();
+
+		if (clearCache) {
+			DfsBlockCache.reconfigure(cfg);
+			db.getObjectDatabase().clearCache();
+		}
+	}
+
+	private void assertPackSize() throws IOException {
+		try (DfsReader ctx = db.getObjectDatabase().newReader();
+				PackWriter pw = new PackWriter(ctx);
+				ByteArrayOutputStream os = new ByteArrayOutputStream();
+				PackOutputStream out = new PackOutputStream(
+						NullProgressMonitor.INSTANCE, os, pw)) {
+			DfsPackFile pack = db.getObjectDatabase().getPacks()[0];
+			long packSize = pack.getPackDescription().getFileSize(PackExt.PACK);
+			pack.copyPackAsIs(out, ctx);
+			assertEquals(packSize - (12 + 20), os.size());
+		}
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java

@@ -464,6 +464,9 @@ public final class DfsPackFile extends BlockBasedFile {
 		while (0 < remaining) {
 			DfsBlock b = cache.getOrLoad(this, position, ctx, () -> rc);
 			int ptr = (int) (position - b.start);
+			if (b.size() <= ptr) {
+				throw packfileIsTruncated();
+			}
 			int n = (int) Math.min(b.size() - ptr, remaining);
 			b.write(out, position, n);
 			position += n;
@@ -481,6 +484,9 @@ public final class DfsPackFile extends BlockBasedFile {
 			DfsBlock b = cache.get(key, alignToBlock(position));
 			if (b != null) {
 				int ptr = (int) (position - b.start);
+				if (b.size() <= ptr) {
+					throw packfileIsTruncated();
+				}
 				int n = (int) Math.min(b.size() - ptr, remaining);
 				b.write(out, position, n);
 				position += n;
@@ -490,23 +496,18 @@ public final class DfsPackFile extends BlockBasedFile {
 				continue;
 			}
 
+			// Need to skip the 'PACK' header for the first read
+			int ptr = packHeadSkipped ? 0 : 12;
 			buf.position(0);
-			int n = read(rc, buf);
-			if (n <= 0) {
+			int bufLen = read(rc, buf);
+			if (bufLen <= ptr) {
 				throw packfileIsTruncated();
-			} else if (n > remaining) {
-				n = (int) remaining;
-			}
-
-			if (!packHeadSkipped) {
-				// Need skip the 'PACK' header for the first read
-				out.write(buf.array(), 12, n - 12);
-				packHeadSkipped = true;
-			} else {
-				out.write(buf.array(), 0, n);
 			}
+			int n = (int) Math.min(bufLen - ptr, remaining);
+			out.write(buf.array(), ptr, n);
 			position += n;
 			remaining -= n;
+			packHeadSkipped = true;
 		}
 		return position;
 	}