/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.jena.riot.system;
import java.util.Map ;
import org.apache.jena.atlas.lib.InternalErrorException ;
/** Maps A's to B's, based on a scope S */
public class MapWithScope<A, B, S>
{
// ======== Interfaces
public interface ScopePolicy<A, B, S>
{
Map<A, B> getScope(S scope) ;
void clear() ;
}
/** Allocate a B, given some A.
* Only called once per instance of B if the ScopePolicy map is non-null.
*/
public interface Allocator<A,B,S>
{
/** Allocate - return the same B for a given A.
* "same" means .equals, not ==
*/
public B alloc(S scope, A item) ;
/** Create a fresh, unique (to within policy) B */
public B create() ;
public void reset() ;
}
// ======== The Object
// To be fully general, we should have an allocator per scope (and have an allocator factory).
// But we don't need that complexity.
private final ScopePolicy<A,B,S> scopePolicy ;
private final Allocator<A,B,S> allocator ;
protected MapWithScope(ScopePolicy<A,B,S> scopePolicy, Allocator<A,B,S> allocator)
{
this.scopePolicy = scopePolicy ;
this.allocator = allocator ;
}
/** Get a B object for an A object in scope S object */
public B get(S scope, A item)
{
if ( item == null )
throw new InternalErrorException("null in MapWithScope.get(,null)") ;
Map<A, B> map = scopePolicy.getScope(scope) ;
if ( map == null )
// No map - no item->allocation tracking.
return allocator.alloc(scope, item) ;
B mappedItem = map.get(item) ;
if ( mappedItem == null )
{
mappedItem = allocator.alloc(scope, item) ;
map.put(item, mappedItem) ;
}
return mappedItem ;
}
/** Create a label that is guaranteed to be fresh */
public B create() { return allocator.create() ; }
/** Clear scope and allocation */
public void clear() { scopePolicy.clear() ; allocator.reset() ; }
}