Use Comparators for PackSource

Rather than requiring callers to do their own computations based on the
package-private "category" number, provide an actual
Comparator<PackSource> instance, and explicitly discourage usage of
default Enum comparison.

Construct the default comparator using a builder pattern based on
defining equivalence classes. This gives us the same behavior as the old
category field in PackSource, with an abstraction that does not leak the
implementation detail of comparing rank numbers.

Change-Id: I6757211397ab1bc181d61298e073f88b69dbefc3

1 files changed, 90 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackSourceTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackSourceTest.java
new file mode 100644
index 0000000000..7bf1f587f8
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackSourceTest.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2018, 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.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.COMPACT;
+import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.DEFAULT_COMPARATOR;
+import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.GC;
+import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.GC_REST;
+import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.GC_TXN;
+import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.INSERT;
+import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.RECEIVE;
+import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.UNREACHABLE_GARBAGE;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class PackSourceTest {
+	@Test
+	public void defaultComaprator() throws Exception {
+		assertEquals(0, DEFAULT_COMPARATOR.compare(INSERT, INSERT));
+		assertEquals(0, DEFAULT_COMPARATOR.compare(RECEIVE, RECEIVE));
+		assertEquals(0, DEFAULT_COMPARATOR.compare(COMPACT, COMPACT));
+		assertEquals(0, DEFAULT_COMPARATOR.compare(GC, GC));
+		assertEquals(0, DEFAULT_COMPARATOR.compare(GC_REST, GC_REST));
+		assertEquals(0, DEFAULT_COMPARATOR.compare(GC_TXN, GC_TXN));
+		assertEquals(0, DEFAULT_COMPARATOR.compare(UNREACHABLE_GARBAGE, UNREACHABLE_GARBAGE));
+
+		assertEquals(0, DEFAULT_COMPARATOR.compare(INSERT, RECEIVE));
+		assertEquals(0, DEFAULT_COMPARATOR.compare(RECEIVE, INSERT));
+
+		assertEquals(-1, DEFAULT_COMPARATOR.compare(INSERT, COMPACT));
+		assertEquals(1, DEFAULT_COMPARATOR.compare(COMPACT, INSERT));
+
+		assertEquals(-1, DEFAULT_COMPARATOR.compare(RECEIVE, COMPACT));
+		assertEquals(1, DEFAULT_COMPARATOR.compare(COMPACT, RECEIVE));
+
+		assertEquals(-1, DEFAULT_COMPARATOR.compare(COMPACT, GC));
+		assertEquals(1, DEFAULT_COMPARATOR.compare(GC, COMPACT));
+
+		assertEquals(-1, DEFAULT_COMPARATOR.compare(GC, GC_REST));
+		assertEquals(1, DEFAULT_COMPARATOR.compare(GC_REST, GC));
+
+		assertEquals(-1, DEFAULT_COMPARATOR.compare(GC_REST, GC_TXN));
+		assertEquals(1, DEFAULT_COMPARATOR.compare(GC_TXN, GC_REST));
+
+		assertEquals(-1, DEFAULT_COMPARATOR.compare(GC_TXN, UNREACHABLE_GARBAGE));
+		assertEquals(1, DEFAULT_COMPARATOR.compare(UNREACHABLE_GARBAGE, GC_TXN));
+	}
+}