// Copyright 2004, 2005, 2006 The Apache Software Foundation | |
// | |
// 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.apache.tapestry5.ioc.internal.util; | |
import java.util.HashMap; | |
import java.util.IdentityHashMap; | |
import java.util.List; | |
import java.util.Map; | |
/** | |
* Used to "uniquify" names within a given context. A base name is passed in, and the return value is the base name, or | |
* the base name extended with a suffix to make it unique. | |
* <p/> | |
* This class is not threadsafe. | |
*/ | |
public final class IdAllocator | |
{ | |
private static final String SEPARATOR = "_"; | |
/** | |
* Map from allocated id to a generator for names associated with the allocated id. | |
*/ | |
private final Map<String, NameGenerator> generatorMap; | |
private final String namespace; | |
/** | |
* Generates unique names with a particular prefix. | |
*/ | |
private static class NameGenerator implements Cloneable | |
{ | |
private final String baseId; | |
private int index; | |
NameGenerator(String baseId) | |
{ | |
this.baseId = baseId + SEPARATOR; | |
} | |
public String nextId() | |
{ | |
return baseId + index++; | |
} | |
/** | |
* Clones this instance, returning an equivalent but seperate copy. | |
*/ | |
@SuppressWarnings({ "CloneDoesntDeclareCloneNotSupportedException" }) | |
@Override | |
public NameGenerator clone() | |
{ | |
try | |
{ | |
return (NameGenerator) super.clone(); | |
} | |
catch (CloneNotSupportedException ex) | |
{ | |
// Unreachable! | |
throw new RuntimeException(ex); | |
} | |
} | |
} | |
/** | |
* Creates a new allocator with no namespace. | |
*/ | |
public IdAllocator() | |
{ | |
this(""); | |
} | |
/** | |
* Creates a new allocator with the provided namespace. | |
*/ | |
public IdAllocator(String namespace) | |
{ | |
this(namespace, new HashMap<String, NameGenerator>()); | |
} | |
private IdAllocator(String namespace, Map<String, NameGenerator> generatorMap) | |
{ | |
this.namespace = namespace; | |
this.generatorMap = generatorMap; | |
} | |
/** | |
* Returns a list of all allocated ids, sorted alphabetically. | |
*/ | |
public List<String> getAllocatedIds() | |
{ | |
return InternalUtils.sortedKeys(generatorMap); | |
} | |
/** | |
* Creates a clone of this IdAllocator instance, copying the allocator's namespace and key map. | |
*/ | |
@SuppressWarnings({ "CloneDoesntCallSuperClone" }) | |
@Override | |
public IdAllocator clone() | |
{ | |
// Copying the generatorMap is tricky; multiple keys will point to the same NameGenerator | |
// instance. We need to clone the NameGenerators, then build a new map around the clones. | |
IdentityHashMap<NameGenerator, NameGenerator> transformMap = new IdentityHashMap<NameGenerator, NameGenerator>(); | |
for (NameGenerator original : generatorMap.values()) | |
{ | |
NameGenerator copy = original.clone(); | |
transformMap.put(original, copy); | |
} | |
Map<String, NameGenerator> mapCopy = CollectionFactory.newMap(); | |
for (String key : generatorMap.keySet()) | |
{ | |
NameGenerator original = generatorMap.get(key); | |
NameGenerator copy = transformMap.get(original); | |
mapCopy.put(key, copy); | |
} | |
return new IdAllocator(namespace, mapCopy); | |
} | |
/** | |
* Allocates the id. Repeated calls for the same name will return "name", "name_0", "name_1", etc. | |
*/ | |
public String allocateId(String name) | |
{ | |
String key = name + namespace; | |
NameGenerator g = generatorMap.get(key); | |
String result; | |
if (g == null) | |
{ | |
g = new NameGenerator(key); | |
result = key; | |
} | |
else result = g.nextId(); | |
// Handle the degenerate case, where a base name of the form "foo_0" has been | |
// requested. Skip over any duplicates thus formed. | |
while (generatorMap.containsKey(result)) result = g.nextId(); | |
generatorMap.put(result, g); | |
return result; | |
} | |
/** | |
* Checks to see if a given name has been allocated. | |
*/ | |
public boolean isAllocated(String name) | |
{ | |
return generatorMap.containsKey(name); | |
} | |
/** | |
* Clears the allocator, resetting it to freshly allocated state. | |
*/ | |
public void clear() | |
{ | |
generatorMap.clear(); | |
} | |
} |