hadoop InMemoryWriter 源码
haddop InMemoryWriter 代码
文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/task/reduce/InMemoryWriter.java
/**
* 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.mapreduce.task.reduce;
import java.io.DataOutputStream;
import java.io.IOException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.BoundedByteArrayOutputStream;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.WritableUtils;
import org.apache.hadoop.mapred.IFile;
import org.apache.hadoop.mapred.IFileOutputStream;
import org.apache.hadoop.mapred.IFile.Writer;
@InterfaceAudience.Private
@InterfaceStability.Unstable
public class InMemoryWriter<K, V> extends Writer<K, V> {
private DataOutputStream out;
public InMemoryWriter(BoundedByteArrayOutputStream arrayStream) {
super(null);
this.out =
new DataOutputStream(new IFileOutputStream(arrayStream));
}
public void append(K key, V value) throws IOException {
throw new UnsupportedOperationException
("InMemoryWriter.append(K key, V value");
}
public void append(DataInputBuffer key, DataInputBuffer value)
throws IOException {
int keyLength = key.getLength() - key.getPosition();
if (keyLength < 0) {
throw new IOException("Negative key-length not allowed: " + keyLength +
" for " + key);
}
int valueLength = value.getLength() - value.getPosition();
if (valueLength < 0) {
throw new IOException("Negative value-length not allowed: " +
valueLength + " for " + value);
}
WritableUtils.writeVInt(out, keyLength);
WritableUtils.writeVInt(out, valueLength);
out.write(key.getData(), key.getPosition(), keyLength);
out.write(value.getData(), value.getPosition(), valueLength);
}
public void close() throws IOException {
// Write EOF_MARKER for key/value length
WritableUtils.writeVInt(out, IFile.EOF_MARKER);
WritableUtils.writeVInt(out, IFile.EOF_MARKER);
// Close the stream
out.close();
out = null;
}
}
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