BitmapWalkerTest: New test for the walker

Change-Id: I414f5bdd86e5623d7669fa187df19e06acd02cef

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/BitmapWalkerTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/BitmapWalkerTest.java
new file mode 100644 (file)
index 0000000..a59a71d
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/BitmapWalkerTest.java
@@ -0,0 +1,161 @@
+/*
+ * Copyright (C) 2023, Google Inc.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.revwalk;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+import java.util.List;
+
+import org.eclipse.jgit.internal.storage.file.FileRepository;
+import org.eclipse.jgit.internal.storage.file.GC;
+import org.eclipse.jgit.junit.LocalDiskRepositoryTestCase;
+import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.BitmapIndex;
+import org.eclipse.jgit.lib.BitmapIndex.Bitmap;
+import org.eclipse.jgit.lib.BitmapIndex.BitmapBuilder;
+import org.eclipse.jgit.lib.BitmapIndex.BitmapLookupListener;
+import org.eclipse.jgit.lib.NullProgressMonitor;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.junit.Before;
+import org.junit.Test;
+
+public class BitmapWalkerTest extends LocalDiskRepositoryTestCase {
+
+       private static final String MAIN = "refs/heads/main";
+
+       TestRepository<FileRepository> repo;
+
+       RevCommit tipWithBitmap;
+
+       @Override
+       @Before
+       public void setUp() throws Exception {
+               super.setUp();
+               FileRepository db = createWorkRepository();
+               repo = new TestRepository<>(db);
+
+               RevCommit base = repo.commit().create();
+               RevCommit one = repo.commit().parent(base).create();
+               tipWithBitmap = repo.commit().parent(one).create();
+               repo.update(MAIN, tipWithBitmap);
+
+               GC gc = new GC(repo.getRepository());
+               gc.setAuto(false);
+               gc.gc().get();
+
+               assertNotNull(repo.getRevWalk().getObjectReader().getBitmapIndex());
+       }
+
+       private static class BitmapWalkCounter implements BitmapLookupListener {
+               int withBitmap;
+
+               int withoutBitmap;
+
+               @Override
+               public void onBitmapFound(AnyObjectId oid) {
+                       withBitmap += 1;
+               }
+
+               @Override
+               public void onBitmapNotFound(AnyObjectId oid) {
+                       withoutBitmap += 1;
+               }
+       }
+
+       @Test
+       public void counters_bitmapAtTip() throws Exception {
+               try (RevWalk rw = repo.getRevWalk();
+                               ObjectReader or = rw.getObjectReader()) {
+                       BitmapWalkCounter counter = new BitmapWalkCounter();
+                       BitmapIndex bitmapIndex = or.getBitmapIndex();
+                       bitmapIndex.addBitmapLookupListener(counter);
+                       BitmapWalker bw = new BitmapWalker(rw.toObjectWalkWithSameObjects(),
+                                       bitmapIndex, NullProgressMonitor.INSTANCE);
+                       BitmapBuilder bitmap = bw.findObjects(List.of(tipWithBitmap), null,
+                                       true);
+                       // First commit has a tree, so in total 4 objects
+                       assertEquals(4, bitmap.cardinality());
+                       assertEquals(1, counter.withBitmap);
+                       assertEquals(0, counter.withoutBitmap);
+                       assertEquals(0, bw.getCountOfBitmapIndexMisses());
+               }
+       }
+
+       @Test
+       public void counters_bitmapAfterAStep() throws Exception {
+               System.out.println("Old tip: " + tipWithBitmap);
+               RevCommit newTip = repo.commit().parent(tipWithBitmap).create();
+               System.out.println("New tip: " + newTip);
+               try (RevWalk rw = repo.getRevWalk();
+                               ObjectReader or = rw.getObjectReader()) {
+                       BitmapWalkCounter counter = new BitmapWalkCounter();
+                       BitmapIndex bitmapIndex = or.getBitmapIndex();
+                       bitmapIndex.addBitmapLookupListener(counter);
+                       BitmapWalker bw = new BitmapWalker(rw.toObjectWalkWithSameObjects(),
+                                       bitmapIndex, NullProgressMonitor.INSTANCE);
+
+                       bw.findObjects(List.of(newTip), null, true);
+
+                       assertEquals(1, counter.withBitmap);
+                       // It checks bitmap before marking as interesting, and again in the
+                       // walk
+                       assertEquals(2, counter.withoutBitmap);
+                       assertEquals(1, bw.getCountOfBitmapIndexMisses());
+               }
+       }
+
+       @Test
+       public void counters_bitmapAfterThreeSteps() throws Exception {
+               RevCommit newOne = repo.commit().parent(tipWithBitmap).create();
+               RevCommit newTwo = repo.commit().parent(newOne).create();
+               RevCommit newTip = repo.commit().parent(newTwo).create();
+
+               try (RevWalk rw = repo.getRevWalk();
+                               ObjectReader or = rw.getObjectReader()) {
+                       BitmapWalkCounter counter = new BitmapWalkCounter();
+                       BitmapIndex bitmapIndex = or.getBitmapIndex();
+                       bitmapIndex.addBitmapLookupListener(counter);
+                       BitmapWalker bw = new BitmapWalker(rw.toObjectWalkWithSameObjects(),
+                                       bitmapIndex, NullProgressMonitor.INSTANCE);
+
+                       bw.findObjects(List.of(newTip), null, true);
+
+                       assertEquals(1, counter.withBitmap);
+                       assertEquals(4, counter.withoutBitmap);
+                       assertEquals(3, bw.getCountOfBitmapIndexMisses());
+               }
+       }
+
+       @Test
+       public void counters_bitmapAfterThreeStepsWithSeen() throws Exception {
+               RevCommit newOne = repo.commit().parent(tipWithBitmap).create();
+               RevCommit newTwo = repo.commit().parent(newOne).create();
+               RevCommit newTip = repo.commit().parent(newTwo).create();
+
+               try (RevWalk rw = repo.getRevWalk();
+                               ObjectReader or = rw.getObjectReader()) {
+                       BitmapIndex bitmapIndex = or.getBitmapIndex();
+                       Bitmap seen = bitmapIndex.getBitmap(tipWithBitmap);
+                       BitmapBuilder seenBB = bitmapIndex.newBitmapBuilder().or(seen);
+                       BitmapWalkCounter counter = new BitmapWalkCounter();
+                       bitmapIndex.addBitmapLookupListener(counter);
+                       BitmapWalker bw = new BitmapWalker(rw.toObjectWalkWithSameObjects(),
+                                       bitmapIndex, NullProgressMonitor.INSTANCE);
+
+                       bw.findObjects(List.of(newTip), seenBB, true);
+
+                       assertEquals(0, counter.withBitmap);
+                       assertEquals(4, counter.withoutBitmap);
+                       assertEquals(3, bw.getCountOfBitmapIndexMisses());
+               }
+       }
+}