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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
stable-5.1
Dave Borowitz 7 years ago
parent
43ec590d0e
commit
e7bacf0a7f
3 changed files with 189 additions and 14 deletions
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  1. 90
      org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackSourceTest.java
  2. 111
      org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsObjDatabase.java
  3. 2
      org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackDescription.java

90
org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackSourceTest.java
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@ -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));
}
}

111
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsObjDatabase.java
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@ -43,13 +43,17 @@
package org.eclipse.jgit.internal.storage.dfs;
import static java.util.stream.Collectors.joining;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
@ -86,10 +90,16 @@ public abstract class DfsObjDatabase extends ObjectDatabase {
}
};
/** Sources for a pack file. */
/**
* Sources for a pack file.
* <p>
* <strong>Note:</strong> When sorting packs by source, do not use the default
* comparator based on {@link Enum#compareTo}. Prefer {@link
* #DEFAULT_COMPARATOR} or your own {@link ComparatorBuilder}.
*/
public static enum PackSource {
/** The pack is created by ObjectInserter due to local activity. */
INSERT(0),
INSERT,
/**
* The pack is created by PackParser due to a network event.
@ -100,7 +110,7 @@ public abstract class DfsObjDatabase extends ObjectDatabase {
* storage layout preferred by this version. Received packs are likely
* to be either compacted or garbage collected in the future.
*/
RECEIVE(0),
RECEIVE,
/**
* The pack was created by compacting multiple packs together.
@ -111,7 +121,7 @@ public abstract class DfsObjDatabase extends ObjectDatabase {
*
* @see DfsPackCompactor
*/
COMPACT(1),
COMPACT,
/**
* Pack was created by Git garbage collection by this implementation.
@ -122,17 +132,17 @@ public abstract class DfsObjDatabase extends ObjectDatabase {
*
* @see DfsGarbageCollector
*/
GC(2),
GC,
/** Created from non-heads by {@link DfsGarbageCollector}. */
GC_REST(3),
GC_REST,
/**
* RefTreeGraph pack was created by Git garbage collection.
*
* @see DfsGarbageCollector
*/
GC_TXN(4),
GC_TXN,
/**
* Pack was created by Git garbage collection.
@ -141,12 +151,86 @@ public abstract class DfsObjDatabase extends ObjectDatabase {
* last GC pass. It is retained in a new pack until it is safe to prune
* these objects from the repository.
*/
UNREACHABLE_GARBAGE(5);
UNREACHABLE_GARBAGE;
/**
* Default comparator for sources.
* <p>
* Sorts generally newer, smaller types such as {@code INSERT} and {@code
* RECEIVE} earlier; older, larger types such as {@code GC} later; and
* {@code UNREACHABLE_GARBAGE} at the end.
*/
public static final Comparator<PackSource> DEFAULT_COMPARATOR =
new ComparatorBuilder()
.add(INSERT, RECEIVE)
.add(COMPACT)
.add(GC)
.add(GC_REST)
.add(GC_TXN)
.add(UNREACHABLE_GARBAGE)
.build();
/**
* Builder for describing {@link PackSource} ordering where some values are
* explicitly considered equal to others.
*/
public static class ComparatorBuilder {
private final Map<PackSource, Integer> ranks = new HashMap<>();
private int counter;
/**
* Add a collection of sources that should sort as equal.
* <p>
* Sources in the input will sort after sources listed in previous calls
* to this method.
*
* @param sources
* sources in this equivalence class.
* @return this.
*/
public ComparatorBuilder add(PackSource... sources) {
for (PackSource s : sources) {
ranks.put(s, Integer.valueOf(counter));
}
counter++;
return this;
}
/**
* Build the comparator.
*
* @return new comparator instance.
* @throws IllegalArgumentException
* not all {@link PackSource} instances were explicitly assigned
* an equivalence class.
*/
public Comparator<PackSource> build() {
return new PackSourceComparator(ranks);
}
}
final int category;
private static class PackSourceComparator implements Comparator<PackSource> {
private final Map<PackSource, Integer> ranks;
PackSource(int category) {
this.category = category;
private PackSourceComparator(Map<PackSource, Integer> ranks) {
if (!ranks.keySet().equals(
new HashSet<>(Arrays.asList(PackSource.values())))) {
throw new IllegalArgumentException();
}
this.ranks = new HashMap<>(ranks);
}
@Override
public int compare(PackSource a, PackSource b) {
return ranks.get(a).compareTo(ranks.get(b));
}
@Override
public String toString() {
return Arrays.stream(PackSource.values())
.map(s -> s + "=" + ranks.get(s)) //$NON-NLS-1$
.collect(joining(", ", getClass().getSimpleName() + "{", "}")); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
}
}
}
@ -588,8 +672,9 @@ public abstract class DfsObjDatabase extends ObjectDatabase {
DfsPackDescription a = fa.getPackDescription();
DfsPackDescription b = fb.getPackDescription();
// GC, COMPACT reftables first by higher category.
int c = b.getPackSource().category - a.getPackSource().category;
// GC, COMPACT reftables first by reversing default order.
int c = PackSource.DEFAULT_COMPARATOR.reversed()
.compare(a.getPackSource(), b.getPackSource());
if (c != 0) {
return c;
}

2
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackDescription.java
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@ -476,7 +476,7 @@ public class DfsPackDescription implements Comparable<DfsPackDescription> {
// Cluster by PackSource, pushing UNREACHABLE_GARBAGE to the end.
PackSource as = getPackSource();
PackSource bs = b.getPackSource();
int cmp = as.category - bs.category;
int cmp = PackSource.DEFAULT_COMPARATOR.compare(as, bs);
if (cmp != 0) {
return cmp;
}

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