| /** |
| * 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.io; |
| |
| import java.io.IOException; |
| import java.io.DataInput; |
| import java.io.DataOutput; |
| import java.io.DataOutputStream; |
| import java.io.DataInputStream; |
| import java.io.ByteArrayOutputStream; |
| import java.io.ByteArrayInputStream; |
| import java.util.zip.Deflater; |
| import java.util.zip.DeflaterOutputStream; |
| import java.util.zip.InflaterInputStream; |
| |
| /** A base-class for Writables which store themselves compressed and lazily |
| * inflate on field access. This is useful for large objects whose fields are |
| * not be altered during a map or reduce operation: leaving the field data |
| * compressed makes copying the instance from one file to another much |
| * faster. */ |
| public abstract class CompressedWritable implements Writable { |
| // if non-null, the compressed field data of this instance. |
| private byte[] compressed; |
| |
| public CompressedWritable() {} |
| |
| public final void readFields(DataInput in) throws IOException { |
| compressed = new byte[in.readInt()]; |
| in.readFully(compressed, 0, compressed.length); |
| } |
| |
| /** Must be called by all methods which access fields to ensure that the data |
| * has been uncompressed. */ |
| protected void ensureInflated() { |
| if (compressed != null) { |
| try { |
| ByteArrayInputStream deflated = new ByteArrayInputStream(compressed); |
| DataInput inflater = |
| new DataInputStream(new InflaterInputStream(deflated)); |
| readFieldsCompressed(inflater); |
| compressed = null; |
| } catch (IOException e) { |
| throw new RuntimeException(e); |
| } |
| } |
| } |
| |
| /** Subclasses implement this instead of {@link #readFields(DataInput)}. */ |
| protected abstract void readFieldsCompressed(DataInput in) |
| throws IOException; |
| |
| public final void write(DataOutput out) throws IOException { |
| if (compressed == null) { |
| ByteArrayOutputStream deflated = new ByteArrayOutputStream(); |
| Deflater deflater = new Deflater(Deflater.BEST_SPEED); |
| DataOutputStream dout = |
| new DataOutputStream(new DeflaterOutputStream(deflated, deflater)); |
| writeCompressed(dout); |
| dout.close(); |
| deflater.end(); |
| compressed = deflated.toByteArray(); |
| } |
| out.writeInt(compressed.length); |
| out.write(compressed); |
| } |
| |
| /** Subclasses implement this instead of {@link #write(DataOutput)}. */ |
| protected abstract void writeCompressed(DataOutput out) throws IOException; |
| |
| } |