// This software is released into the Public Domain. See copying.txt for details.
package org.openstreetmap.osmosis.xml.common;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.zip.GZIPOutputStream;
import org.apache.commons.compress.compressors.bzip2.BZip2CompressorInputStream;
import org.apache.commons.compress.compressors.bzip2.BZip2CompressorOutputStream;
import org.openstreetmap.osmosis.core.OsmosisRuntimeException;
import org.openstreetmap.osmosis.core.util.MultiMemberGZIPInputStream;
/**
* A utility class for layering compression streams on top of underlying byte
* streams based upon a specified compression algorithm.
*
* @author Brett Henderson
*/
public class CompressionActivator {
private CompressionMethod compressionMethod;
/**
* Creates a new instance.
*
* @param compressionMethod
* The compression method to employ.
*/
public CompressionActivator(CompressionMethod compressionMethod) {
this.compressionMethod = compressionMethod;
}
/**
* Wraps a compression stream around the destination stream based upon the
* requested compression method. If this method returns successfully, the
* input destination stream does not require closing after use because it
* will be closed when the returned output stream is closed.
*
* @param destinationStream
* The destination stream for receiving compressed data.
* @return A stream for writing compressed data to the destination stream.
*/
public OutputStream createCompressionOutputStream(OutputStream destinationStream) {
try {
if (CompressionMethod.None.equals(compressionMethod)) {
return destinationStream;
}
if (CompressionMethod.GZip.equals(compressionMethod)) {
return new GZIPOutputStream(destinationStream);
}
if (CompressionMethod.BZip2.equals(compressionMethod)) {
return new BZip2CompressorOutputStream(destinationStream);
}
throw new OsmosisRuntimeException("Compression method " + compressionMethod + " is not recognized.");
} catch (IOException e) {
throw new OsmosisRuntimeException(
"Unable to instantiate a " + compressionMethod + " compression stream.", e);
}
}
/**
* Wraps a compression stream around the source stream based upon the
* requested compression method. If this method returns successfully, the
* input source stream does not require closing after use because it will be
* closed when the returned input stream is closed.
*
* @param sourceStream
* The source stream for providing compressed data.
* @return A stream for writing compressed data to the destination stream.
*/
public InputStream createCompressionInputStream(InputStream sourceStream) {
try {
if (CompressionMethod.None.equals(compressionMethod)) {
return sourceStream;
}
if (CompressionMethod.GZip.equals(compressionMethod)) {
return new MultiMemberGZIPInputStream(sourceStream);
}
if (CompressionMethod.BZip2.equals(compressionMethod)) {
return new BZip2CompressorInputStream(sourceStream);
}
throw new OsmosisRuntimeException("Compression method " + compressionMethod + " is not recognized.");
} catch (IOException e) {
throw new OsmosisRuntimeException(
"Unable to instantiate a " + compressionMethod + " compression stream.", e);
}
}
}