| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.giraph.utils; |
| |
| import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration; |
| import org.apache.giraph.edge.OutEdges; |
| import org.apache.giraph.graph.Vertex; |
| import org.apache.hadoop.io.Writable; |
| import org.apache.hadoop.io.WritableComparable; |
| |
| import java.io.IOException; |
| |
| /** |
| * Iterates over vertices stored in an ExtendedDataOutput such that |
| * the ownership of the vertex id can be transferred to another object. |
| * This optimization cuts down on the number of objects instantiated and |
| * garbage collected |
| * |
| * @param <I> Vertex id |
| * @param <V> Vertex value |
| * @param <E> Edge value |
| */ |
| public class VertexIterator<I extends WritableComparable, |
| V extends Writable, E extends Writable> { |
| /** Reader of the serialized edges */ |
| private final ExtendedDataInput extendedDataInput; |
| /** Current vertex */ |
| private Vertex<I, V, E> vertex; |
| /** Configuration */ |
| private final ImmutableClassesGiraphConfiguration<I, V, E> configuration; |
| |
| /** |
| * Constructor. |
| * |
| * @param extendedDataOutput Extended data output |
| * @param configuration Configuration |
| */ |
| public VertexIterator( |
| ExtendedDataOutput extendedDataOutput, |
| ImmutableClassesGiraphConfiguration<I, V, E> configuration) { |
| extendedDataInput = configuration.createExtendedDataInput( |
| extendedDataOutput.getByteArray(), 0, extendedDataOutput.getPos()); |
| this.configuration = configuration; |
| resetEmptyVertex(); |
| } |
| |
| /** |
| * Reset the empty Vertex to an initial state. |
| */ |
| private void resetEmptyVertex() { |
| vertex = configuration.createVertex(); |
| I id = configuration.createVertexId(); |
| V value = configuration.createVertexValue(); |
| OutEdges<I, E> edges = configuration.createOutEdges(); |
| vertex.initialize(id, value, edges); |
| } |
| |
| /** |
| * Returns true if the iteration has more elements. |
| * |
| * @return True if the iteration has more elements. |
| */ |
| public boolean hasNext() { |
| return !extendedDataInput.endOfInput(); |
| } |
| |
| /** |
| * Moves to the next element in the iteration. |
| */ |
| public void next() { |
| // If the vertex was released, create another one |
| if (vertex == null) { |
| resetEmptyVertex(); |
| } |
| |
| // If the vertex id was released, create another one |
| if (vertex.getId() == null) { |
| vertex.initialize(configuration.createVertexId(), vertex.getValue()); |
| } |
| |
| try { |
| WritableUtils.reinitializeVertexFromDataInput( |
| extendedDataInput, vertex, configuration); |
| } catch (IOException e) { |
| throw new IllegalStateException("next: IOException", e); |
| } |
| } |
| |
| /** |
| * Get the current vertex id. Ihis object's contents are only guaranteed |
| * until next() is called. To take ownership of this object call |
| * releaseCurrentVertexId() after getting a reference to this object. |
| * |
| * @return Current vertex id |
| */ |
| public I getCurrentVertexId() { |
| return vertex.getId(); |
| } |
| |
| /** |
| * The backing store of the current vertex id is now released. |
| * Further calls to getCurrentVertexId () without calling next() |
| * will return null. |
| * |
| * @return Current vertex id that was released |
| */ |
| public I releaseCurrentVertexId() { |
| I releasedVertexId = vertex.getId(); |
| vertex.initialize(null, vertex.getValue()); |
| return releasedVertexId; |
| } |
| |
| public Vertex<I, V, E> getVertex() { |
| return vertex; |
| } |
| |
| /** |
| * Release the ownership of the Vertex object to the caller |
| * |
| * @return Released Vertex object |
| */ |
| public Vertex<I, V, E> releaseVertex() { |
| Vertex<I, V, E> releasedVertex = vertex; |
| vertex = null; |
| return releasedVertex; |
| } |
| } |