StreamBackedIterator.java
上传用户:quxuerui
上传日期:2018-01-08
资源大小:41811k
文件大小:3k
- /**
- * 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.hadoop.mapred.join;
- import java.io.ByteArrayInputStream;
- import java.io.ByteArrayOutputStream;
- import java.io.DataInputStream;
- import java.io.DataOutputStream;
- import java.io.IOException;
- import org.apache.hadoop.io.Writable;
- /**
- * This class provides an implementation of ResetableIterator. This
- * implementation uses a byte array to store elements added to it.
- */
- public class StreamBackedIterator<X extends Writable>
- implements ResetableIterator<X> {
- private static class ReplayableByteInputStream extends ByteArrayInputStream {
- public ReplayableByteInputStream(byte[] arr) {
- super(arr);
- }
- public void resetStream() {
- mark = 0;
- reset();
- }
- }
- private ByteArrayOutputStream outbuf = new ByteArrayOutputStream();
- private DataOutputStream outfbuf = new DataOutputStream(outbuf);
- private ReplayableByteInputStream inbuf;
- private DataInputStream infbuf;
- public StreamBackedIterator() { }
- public boolean hasNext() {
- return infbuf != null && inbuf.available() > 0;
- }
- public boolean next(X val) throws IOException {
- if (hasNext()) {
- inbuf.mark(0);
- val.readFields(infbuf);
- return true;
- }
- return false;
- }
- public boolean replay(X val) throws IOException {
- inbuf.reset();
- if (0 == inbuf.available())
- return false;
- val.readFields(infbuf);
- return true;
- }
- public void reset() {
- if (null != outfbuf) {
- inbuf = new ReplayableByteInputStream(outbuf.toByteArray());
- infbuf = new DataInputStream(inbuf);
- outfbuf = null;
- }
- inbuf.resetStream();
- }
- public void add(X item) throws IOException {
- item.write(outfbuf);
- }
- public void close() throws IOException {
- if (null != infbuf)
- infbuf.close();
- if (null != outfbuf)
- outfbuf.close();
- }
- public void clear() {
- if (null != inbuf)
- inbuf.resetStream();
- outbuf.reset();
- outfbuf = new DataOutputStream(outbuf);
- }
- }