PackBitmapIndex/StoredBitmap: Expose size and counts

PackBitmapIndex holds a collection of StoredBitmaps. StoredBitmaps can
be either base bitmaps (ready) or an XOR over another bitmap. XOR
bitmaps are replaced with a resolved version on demand. Bitmaps
can use a significant amount of memory but we don't have detailed
visibility about it.

Add methods to PackBitmapIndex to know how many xor/bases we have and
their sizes.

Change-Id: I57aa80a1f07ddf9223eb34cfda85aab85529ea9c

2 files changed, 166 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/BasePackBitmapIndexTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/BasePackBitmapIndexTest.java
new file mode 100644
index 0000000000..f47c385ab9
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/BasePackBitmapIndexTest.java
@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2023, Google LLC  and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.internal.storage.file;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.eclipse.jgit.internal.storage.file.BasePackBitmapIndex.StoredBitmap;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectIdOwnerMap;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.googlecode.javaewah.EWAHCompressedBitmap;
+
+public class BasePackBitmapIndexTest {
+
+	private ObjectId baseOid;
+
+	private StoredBitmap baseBitmap;
+
+	private ObjectId xorOid;
+
+	private StoredBitmap xorBitmap;
+
+	private ObjectIdOwnerMap<StoredBitmap> bitmaps;
+
+	@Before
+	public void setUp() {
+		baseOid = ObjectId
+				.fromString("c46f36f2bfc96d6d6f75bd71ee33625293aee690");
+		baseBitmap = newBaseStoredBitmap(baseOid, bitmapOf(100));
+		xorOid = ObjectId
+				.fromString("52c18ae15f8fa3787f920e68791367dae2e1af2d");
+		xorBitmap = newXorStoredBitmap(xorOid, bitmapOf(200, 300), baseBitmap);
+		bitmaps = new ObjectIdOwnerMap<>();
+		bitmaps.add(baseBitmap);
+		bitmaps.add(xorBitmap);
+	}
+
+	@Test
+	public void testBitmapCounts() {
+		TestPackBitmapIndex index = new TestPackBitmapIndex(bitmaps);
+
+		assertEquals(1, index.getBaseBitmapCount());
+		assertEquals(1, index.getXorBitmapCount());
+		assertEquals(2, index.getBitmapCount());
+	}
+
+	@Test
+	public void testBitmapCounts_xorResolved() {
+		TestPackBitmapIndex index = new TestPackBitmapIndex(bitmaps);
+		index.getBitmap(xorOid);
+
+		assertEquals(2, index.getBaseBitmapCount());
+		assertEquals(0, index.getXorBitmapCount());
+		assertEquals(2, index.getBitmapCount());
+	}
+
+	@Test
+	public void testBitmapSizes() {
+		TestPackBitmapIndex index = new TestPackBitmapIndex(bitmaps);
+
+		assertEquals(baseBitmap.getCurrentSizeInBytes(),
+				index.getBaseBitmapSizeInBytes());
+		assertEquals(xorBitmap.getCurrentSizeInBytes(),
+				index.getXorBitmapSizeInBytes());
+	}
+
+	@Test
+	public void testBitmapSizes_xorResolved() {
+		TestPackBitmapIndex index = new TestPackBitmapIndex(bitmaps);
+		index.getBitmap(xorOid);
+
+		assertTrue(baseBitmap.getCurrentSizeInBytes() < index
+				.getBaseBitmapSizeInBytes());
+		assertEquals(0, index.getXorBitmapSizeInBytes());
+	}
+
+	private static final StoredBitmap newBaseStoredBitmap(ObjectId oid,
+			EWAHCompressedBitmap base) {
+		return new StoredBitmap(oid, base, null, 0);
+	}
+
+	private static StoredBitmap newXorStoredBitmap(ObjectId oid,
+			EWAHCompressedBitmap xorMask, StoredBitmap base) {
+		return new StoredBitmap(oid, xorMask, base, 0);
+	}
+
+	private static final EWAHCompressedBitmap bitmapOf(int... bits) {
+		EWAHCompressedBitmap b = new EWAHCompressedBitmap();
+		for (int bit : bits)
+			b.set(bit);
+		return b;
+	}
+
+	private static class TestPackBitmapIndex extends BasePackBitmapIndex {
+		TestPackBitmapIndex(ObjectIdOwnerMap<StoredBitmap> bitmaps) {
+			super(bitmaps);
+		}
+
+		@Override
+		public int findPosition(AnyObjectId objectId) {
+			throw new IllegalStateException();
+		}
+
+		@Override
+		public ObjectId getObject(int position)
+				throws IllegalArgumentException {
+			throw new IllegalStateException();
+		}
+
+		@Override
+		public EWAHCompressedBitmap ofObjectType(EWAHCompressedBitmap bitmap,
+				int type) {
+			throw new IllegalStateException();
+		}
+
+		@Override
+		public int getObjectCount() {
+			throw new IllegalStateException();
+		}
+
+		@Override
+		public int getBitmapCount() {
+			return getBitmaps().size();
+		}
+	}
+}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/StoredBitmapTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/StoredBitmapTest.java
index f5c7c67c5d..684ee52b4a 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/StoredBitmapTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/StoredBitmapTest.java
@@ -11,6 +11,8 @@
 package org.eclipse.jgit.internal.storage.file;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import org.eclipse.jgit.internal.storage.file.BasePackBitmapIndex.StoredBitmap;
 import org.eclipse.jgit.lib.ObjectId;
@@ -44,6 +46,33 @@ public class StoredBitmapTest {
 		assertEquals(bitmapOf(50, 90), sb.getBitmap());
 	}
 
+	@Test
+	public void testGetSizeWithoutXor() {
+		EWAHCompressedBitmap base = bitmapOf(100);
+		StoredBitmap sb = newStoredBitmap(base);
+		assertEquals(base.sizeInBytes(), sb.getCurrentSizeInBytes());
+		sb.getBitmap();
+		assertEquals(base.sizeInBytes(), sb.getCurrentSizeInBytes());
+	}
+
+	@Test
+	public void testGetSizeWithOneXor() {
+		EWAHCompressedBitmap base = bitmapOf(100, 101);
+		EWAHCompressedBitmap xor = bitmapOf(100);
+		StoredBitmap sb = newStoredBitmap(base, xor);
+		assertEquals(xor.sizeInBytes(), sb.getCurrentSizeInBytes());
+	}
+
+	@Test
+	public void testIsBase() {
+		EWAHCompressedBitmap one = bitmapOf(100, 101);
+		EWAHCompressedBitmap two = bitmapOf(100);
+		StoredBitmap baseBitmap = newStoredBitmap(one);
+		StoredBitmap xoredBitmap = newStoredBitmap(one, two);
+		assertTrue(baseBitmap.isBase());
+		assertFalse(xoredBitmap.isBase());
+	}
+
 	private static final StoredBitmap newStoredBitmap(
 			EWAHCompressedBitmap... bitmaps) {
 		StoredBitmap sb = null;