/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.tools.perflib.heap.analysis;
import com.android.annotations.NonNull;
import com.android.tools.perflib.heap.Instance;
import com.android.tools.perflib.heap.Snapshot;
import com.android.tools.perflib.heap.Visitor;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import java.util.List;
import gnu.trove.TLongHashSet;
public class TopologicalSort {
@NonNull
public static ImmutableList<Instance> compute(@NonNull Iterable<? extends Instance> roots) {
TopologicalSortVisitor visitor = new TopologicalSortVisitor();
for (Instance root : roots) {
root.accept(visitor);
}
ImmutableList<Instance> instances = visitor.getOrderedInstances();
// We add the special sentinel node as the single root of the object graph, to ensure the
// dominator algorithm terminates when having to choose between two GC roots.
Snapshot.SENTINEL_ROOT.setTopologicalOrder(0);
// Set localIDs in the range 1..keys.size(). This simplifies the algorithm & data structures
// for dominator computation.
int currentIndex = 0;
for (Instance node : instances) {
node.setTopologicalOrder(++currentIndex);
}
return instances;
}
private static class TopologicalSortVisitor implements Visitor {
private final TLongHashSet mVisited = new TLongHashSet();
private final List<Instance> mPostorder = Lists.newArrayList();
@Override
public boolean visitEnter(Instance instance) {
return mVisited.add(instance.getId());
}
@Override
public void visitLeave(Instance instance) {
mPostorder.add(instance);
}
ImmutableList<Instance> getOrderedInstances() {
return ImmutableList.copyOf(Lists.reverse(mPostorder));
}
}
}