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package org.apache.qpid.nclient.util;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import org.apache.qpid.transport.DeliveryProperties;
import org.apache.qpid.transport.MessageProperties;
import org.apache.qpid.transport.Header;
import org.apache.qpid.api.Message;
/**
* FileMessage provides pull style semantics for
* larges messages backed by a disk.
* Instead of loading all data into memeory it uses
* FileChannel to map regions of the file into memeory
* at a time.
*
* The write methods are not supported.
*
* From the standpoint of performance it is generally
* only worth mapping relatively large files into memory.
*
* FileMessage msg = new FileMessage(in,delProps,msgProps);
* session.messageTransfer(dest,msg,0,0);
*
* The messageTransfer method will read the file in chunks
* and stream it.
*
*/
public class FileMessage extends ReadOnlyMessage implements Message
{
private FileChannel _fileChannel;
private int _chunkSize;
private long _fileSize;
private long _pos = 0;
public FileMessage(FileInputStream in,int chunkSize,DeliveryProperties deliveryProperties,MessageProperties messageProperties)throws IOException
{
_messageProperties = messageProperties;
_deliveryProperties = deliveryProperties;
_fileChannel = in.getChannel();
_chunkSize = chunkSize;
_fileSize = _fileChannel.size();
if (_fileSize <= _chunkSize)
{
_chunkSize = (int)_fileSize;
}
}
public void setHeader(Header header) {
//To change body of implemented methods use File | Settings | File Templates.
}
public Header getHeader() {
return null; //To change body of implemented methods use File | Settings | File Templates.
}
public void readData(byte[] target) throws IOException
{
throw new UnsupportedOperationException();
}
public ByteBuffer readData() throws IOException
{
if (_pos == _fileSize)
{
throw new EOFException();
}
if (_pos + _chunkSize > _fileSize)
{
_chunkSize = (int)(_fileSize - _pos);
}
MappedByteBuffer bb = _fileChannel.map(FileChannel.MapMode.READ_ONLY, _pos, _chunkSize);
_pos += _chunkSize;
return bb;
}
/**
* This message is used by an application user to
* provide data to the client library using pull style
* semantics. Since the message is not transfered yet, it
* does not have a transfer id. Hence this method is not
* applicable to this implementation.
*/
public int getMessageTransferId()
{
throw new UnsupportedOperationException();
}
}
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