/**
* 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.crunch.io.seq;
import java.io.IOException;
import java.util.Iterator;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.crunch.MapFn;
import org.apache.crunch.fn.IdentityFn;
import org.apache.crunch.io.FileReaderFactory;
import org.apache.crunch.io.impl.AutoClosingIterator;
import org.apache.crunch.types.Converter;
import org.apache.crunch.types.PTableType;
import org.apache.crunch.types.PType;
import org.apache.crunch.types.writable.Writables;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.ReflectionUtils;
import com.google.common.collect.Iterators;
import com.google.common.collect.UnmodifiableIterator;
public class SeqFileReaderFactory<T> implements FileReaderFactory<T> {
private static final Log LOG = LogFactory.getLog(SeqFileReaderFactory.class);
private final Converter converter;
private final MapFn<Object, T> mapFn;
private final Writable key;
private final Writable value;
public SeqFileReaderFactory(PType<T> ptype) {
this.converter = ptype.getConverter();
this.mapFn = ptype.getInputMapFn();
if (ptype instanceof PTableType) {
PTableType ptt = (PTableType) ptype;
this.key = SeqFileHelper.newInstance(ptt.getKeyType(), null);
this.value = SeqFileHelper.newInstance(ptt.getValueType(), null);
} else {
this.key = NullWritable.get();
this.value = SeqFileHelper.newInstance(ptype, null);
}
}
public SeqFileReaderFactory(Class clazz) {
PType<T> ptype = Writables.writables(clazz);
this.converter = ptype.getConverter();
this.mapFn = ptype.getInputMapFn();
this.key = NullWritable.get();
this.value = (Writable) ReflectionUtils.newInstance(clazz, null);
}
@Override
public Iterator<T> read(FileSystem fs, final Path path) {
mapFn.initialize();
try {
final SequenceFile.Reader reader = new SequenceFile.Reader(fs, path, fs.getConf());
return new AutoClosingIterator<T>(reader, new UnmodifiableIterator<T>() {
boolean nextChecked = false;
boolean hasNext = false;
@Override
public boolean hasNext() {
if (nextChecked == true) {
return hasNext;
}
try {
hasNext = reader.next(key, value);
nextChecked = true;
return hasNext;
} catch (IOException e) {
LOG.info("Error reading from path: " + path, e);
return false;
}
}
@Override
public T next() {
if (!nextChecked && !hasNext()) {
return null;
}
nextChecked = false;
return mapFn.map(converter.convertInput(key, value));
}
});
} catch (IOException e) {
LOG.info("Could not read seqfile at path: " + path, e);
return Iterators.emptyIterator();
}
}
}