| /** |
| * 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 org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.fs.FileSystem; |
| import org.apache.hadoop.fs.Path; |
| |
| /** A file-based set of keys. */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Stable |
| public class SetFile extends MapFile { |
| |
| protected SetFile() {} // no public ctor |
| |
| /** |
| * Write a new set file. |
| */ |
| public static class Writer extends MapFile.Writer { |
| |
| /** Create the named set for keys of the named class. |
| * @deprecated pass a Configuration too |
| */ |
| public Writer(FileSystem fs, String dirName, |
| Class<? extends WritableComparable> keyClass) throws IOException { |
| super(new Configuration(), fs, dirName, keyClass, NullWritable.class); |
| } |
| |
| /** Create a set naming the element class and compression type. */ |
| public Writer(Configuration conf, FileSystem fs, String dirName, |
| Class<? extends WritableComparable> keyClass, |
| SequenceFile.CompressionType compress) |
| throws IOException { |
| this(conf, fs, dirName, WritableComparator.get(keyClass), compress); |
| } |
| |
| /** Create a set naming the element comparator and compression type. */ |
| public Writer(Configuration conf, FileSystem fs, String dirName, |
| WritableComparator comparator, |
| SequenceFile.CompressionType compress) throws IOException { |
| super(conf, new Path(dirName), |
| comparator(comparator), |
| valueClass(NullWritable.class), |
| compression(compress)); |
| } |
| |
| /** Append a key to a set. The key must be strictly greater than the |
| * previous key added to the set. */ |
| public void append(WritableComparable key) throws IOException{ |
| append(key, NullWritable.get()); |
| } |
| } |
| |
| /** Provide access to an existing set file. */ |
| public static class Reader extends MapFile.Reader { |
| |
| /** Construct a set reader for the named set.*/ |
| public Reader(FileSystem fs, String dirName, Configuration conf) throws IOException { |
| super(fs, dirName, conf); |
| } |
| |
| /** Construct a set reader for the named set using the named comparator.*/ |
| public Reader(FileSystem fs, String dirName, WritableComparator comparator, Configuration conf) |
| throws IOException { |
| super(new Path(dirName), conf, comparator(comparator)); |
| } |
| |
| // javadoc inherited |
| @Override |
| public boolean seek(WritableComparable key) |
| throws IOException { |
| return super.seek(key); |
| } |
| |
| /** Read the next key in a set into <code>key</code>. Returns |
| * true if such a key exists and false when at the end of the set. */ |
| public boolean next(WritableComparable key) |
| throws IOException { |
| return next(key, NullWritable.get()); |
| } |
| |
| /** Read the matching key from a set into <code>key</code>. |
| * Returns <code>key</code>, or null if no match exists. */ |
| public WritableComparable get(WritableComparable key) |
| throws IOException { |
| if (seek(key)) { |
| next(key); |
| return key; |
| } else |
| return null; |
| } |
| } |
| |
| } |