/*
* Copyright 1999-2006 University of Chicago
*
* 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 org.dcache.ftp.client;
import java.io.IOException;
/**
* Data channel uses this interface to read outgoing data.
* Implement it to provide your own ways of reading data.
* It must be thread safe; in parallel transfer mode several
* streams may attempt to read.
**/
public interface DataSource
{
/**
* Reads a data buffer from this data source.
*
* @return The data buffer read. Null, if there is
* no more data to be read.
* @throws IOException if an I/O error occurs.
*/
Buffer read()
throws IOException;
/**
* Closes this data source and releases any system
* resources associated with this source.
*
* @throws IOException if an I/O error occurs.
*/
void close()
throws IOException;
/**
* Optional operation. Returns the total size, in bytes, of the
* data in this source. If the implementation is not able to
* provide a total size for the data source, it should return
* -1
*
* @throws IOException if an I/O exception occurs
*/
long totalSize() throws IOException;
}