/*
* Copyright 2012-present Facebook, Inc.
*
* 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.facebook.buck.graph;
/**
* Class that performs a "bottom-up" traversal of a DAG. For any given node, every node to which it
* has an outgoing edge will be visited before the given node.
*/
public abstract class AbstractBottomUpTraversal<T, E extends Throwable> {
private final TraversableGraph<T> graph;
public AbstractBottomUpTraversal(TraversableGraph<T> graph) {
this.graph = graph;
}
public final void traverse() throws E {
Iterable<T> roots = graph.getNodesWithNoIncomingEdges();
GraphTraversable<T> graphTraversable = node -> graph.getOutgoingNodesFor(node).iterator();
try {
for (T node : new AcyclicDepthFirstPostOrderTraversal<>(graphTraversable).traverse(roots)) {
visit(node);
}
} catch (AcyclicDepthFirstPostOrderTraversal.CycleException e) {
throw new IllegalStateException(
"Cycle detected despite graph which was claimed to be a DAG", e);
}
}
public abstract void visit(T node) throws E;
}