/**
* Copyright 2013 Cloudera Inc.
*
* Licensed 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 com.cloudera.cdk.data.filesystem;
import com.cloudera.cdk.data.DatasetDescriptor;
import com.cloudera.cdk.data.DatasetReader;
import com.cloudera.cdk.data.DatasetReaderException;
import com.cloudera.cdk.data.Format;
import com.cloudera.cdk.data.Formats;
import com.cloudera.cdk.data.UnknownFormatException;
import com.cloudera.cdk.data.spi.AbstractDatasetReader;
import com.cloudera.cdk.data.spi.ReaderWriterState;
import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import java.util.Iterator;
import java.util.NoSuchElementException;
class MultiFileDatasetReader<E> extends AbstractDatasetReader<E> {
private final FileSystem fileSystem;
private final DatasetDescriptor descriptor;
private final Iterator<Path> filesIter;
private DatasetReader<E> reader = null;
private ReaderWriterState state;
public MultiFileDatasetReader(FileSystem fileSystem, Iterable<Path> files,
DatasetDescriptor descriptor) {
Preconditions.checkArgument(fileSystem != null, "FileSystem cannot be null");
Preconditions.checkArgument(descriptor != null, "Descriptor cannot be null");
Preconditions.checkArgument(files != null, "Descriptor cannot be null");
this.fileSystem = fileSystem;
this.descriptor = descriptor;
this.filesIter = files.iterator();
this.state = ReaderWriterState.NEW;
}
@Override
public void open() {
Preconditions.checkState(state.equals(ReaderWriterState.NEW),
"A reader may not be opened more than once - current state:%s", state);
final Format format = descriptor.getFormat();
if (!(Formats.AVRO.equals(format) || Formats.PARQUET.equals(format)
|| Formats.CSV.equals(format))) {
throw new UnknownFormatException("Cannot open format:" + format.getName());
}
this.state = ReaderWriterState.OPEN;
}
@SuppressWarnings("unchecked") // See https://github.com/Parquet/parquet-mr/issues/106
private void openNextReader() {
if (Formats.PARQUET.equals(descriptor.getFormat())) {
reader = new ParquetFileSystemDatasetReader(fileSystem, filesIter.next(),
descriptor.getSchema());
} else if (Formats.CSV.equals(descriptor.getFormat())) {
reader = new CSVFileReader<E>(fileSystem, filesIter.next(), descriptor);
} else {
reader = new FileSystemDatasetReader<E>(fileSystem, filesIter.next(),
descriptor.getSchema());
}
reader.open();
}
@Override
public boolean hasNext() {
Preconditions.checkState(state.equals(ReaderWriterState.OPEN),
"Attempt to read from a file in state:%s", state);
while (true) {
if (reader == null) {
if (filesIter.hasNext()) {
openNextReader();
} else {
return false;
}
} else {
if (reader.hasNext()) {
return true;
} else {
reader.close();
reader = null;
}
}
}
}
@Override
public E next() {
Preconditions.checkState(state.equals(ReaderWriterState.OPEN),
"Attempt to read from a file in state:%s", state);
if (hasNext()) {
// if hasNext => true, then reader is guaranteed to be non-null
return reader.next();
} else {
throw new NoSuchElementException();
}
}
@Override
public void remove() {
Preconditions.checkState(state.equals(ReaderWriterState.OPEN),
"Attempt to remove from a file in state:%s", state);
if (reader == null) {
// If next succeeds, then reader cannot be null. If the reader is null,
// then next did not succeed or hasNext has been used and the reader is
// gone. We could keep track of the last reader that next returned a value
// from, but it probably isn't worth it.
throw new IllegalStateException(
"Remove can only be called after next() returns a value and before calling hasNext()");
}
reader.remove();
}
@Override
public void close() {
if (!state.equals(ReaderWriterState.OPEN)) {
return;
}
if (reader != null) {
reader.close();
}
state = ReaderWriterState.CLOSED;
}
@Override
public boolean isOpen() {
return state.equals(ReaderWriterState.OPEN);
}
@Override
public String toString() {
return Objects.toStringHelper(this)
.add("fileSystem", fileSystem)
.add("descriptor", descriptor)
.add("filesIter", filesIter)
.add("reader", reader)
.add("state", state)
.toString();
}
}