TransferContext.java

/*
 * 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.dc;

/**
 * Represents an environment shared by all data channels
 * performing the same transfer.
 **/
public interface TransferContext
{

    /**
     * A thread can ask for a quit token to perform the operations associated with closing the transfer.
     * The token is interpreted as a permission to perform these operations. The reason for such policy
     * lies mainly in the nature of multithreaded transfer, where there are many transfer threads sharing
     * the same context, but the closing should be done only once.
     *
     * @return a non-null token is a permission for closing, null means no permission.
     **/
    Object getQuitToken();
}