TailIdentityHashMap.java
/*
** Module : TailIdentityHashMap.java
** Abstract : Dictionary that supports registering new items in a new dictionary while iterating.
**
** Copyright (c) 2022, Golden Code Development Corporation.
**
** -#- -I- --Date-- --JPRM-- ----------------------------Description----------------------------
** 001 TW 20220617 Initial implementation.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
** You must preserve all legal notices or author attributions in the covered
** work or Appropriate Legal Notices displayed by works containing the covered
** work. You may not remove from the covered work any author or developer
** credit already included within the covered work.
**
** 1. No License To Use Trademarks.
**
** This license does not grant any license or rights to use the trademarks
** Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
** of Golden Code Development Corporation. You are not authorized to use the
** name Golden Code, FWD, or the names of any author or contributor, for
** publicity purposes without written authorization.
**
** 2. No Misrepresentation of Affiliation.
**
** You may not represent yourself as Golden Code Development Corporation or FWD.
**
** You may not represent yourself for publicity purposes as associated with
** Golden Code Development Corporation, FWD, or any author or contributor to
** the covered work, without written authorization.
**
** 3. No Misrepresentation of Source or Origin.
**
** You may not represent the covered work as solely your work. All modified
** versions of the covered work must be marked in a reasonable way to make it
** clear that the modified work is not originating from Golden Code Development
** Corporation or FWD. All modified versions must contain the notices of
** attribution required in this license.
*/
package com.goldencode.p2j.util;
import java.util.*;
import static com.goldencode.p2j.util.TailMapInternal.*;
/**
* A dictionary that supports registering new items in a
* new Map tail while iterating the collection.
*
* @param <K>
* Dictionary key type
* @param <V>
* Dictionary value type
*/
public class TailIdentityHashMap<K, V>
extends IdentityHashMap<K, V>
implements TailMapInternal<K, V>
{
/** Generated version UID */
private static final long serialVersionUID = 8374591041603079207L;
/** Flag iterating state */
private boolean iteratingActive = false;
/** Prevents nested use of IteratingActive */
private AutoCloseable iteratingActiveSegment = null;
/**
* If {@link #iteratingActive} is true, new items
* are added to {@link #tailingMap}, since adding while iterating is
* prohibited.
* Use {@link #pop} to take control of this tail dictionary.
* The caller is responsible for iterating the tail.
*/
private Map<K, V> tailingMap = null;
/**
* Default constructor.
*/
public TailIdentityHashMap()
{
super();
}
/**
* Constructor with expected maximum size.
*
* @param expectedMaxSize
* The expected maximum size of the hash map.
*/
public TailIdentityHashMap(int expectedMaxSize)
{
super(expectedMaxSize);
}
/**
* Do a 'pop' of the single tail dictionary.
* The caller is responsible for iterating it.
*
* @return <code>null</code> if no tail map present, otherwise a map with at least one item.
*/
public Map<K, V> pop()
{
Map<K, V> ret = tailingMap;
tailingMap = null;
return ret;
}
/**
* Add or replace a key value pair at this key.
*
* @return <code>V</code>
*/
@Override
public V put(K key, V value)
{
return putAtDefault(this, key) ?
super.put(key, value) :
getOrCreateTailingMap().put(key, value);
}
/**
* Reports if this dictionary has the "being iterated" flag.
*
* @return <code>true</code> if this dictionary is being iterated.
*/
public boolean isIteratingActive()
{
return iteratingActive;
}
/**
* The caller is responsible for setting the iterating active flag, by
* implementing a <code>try(AutoCloseable obj = dict.flagIterating())</code>
* block.
*
* @return a new AutoClosable object.
*/
public AutoCloseable flagIterating()
{
if (iteratingActiveSegment != null)
{
throw new UnsupportedOperationException();
}
iteratingActiveSegment = new TailMapAutoClosable<>(this);
return iteratingActiveSegment;
}
/**
* Sets the iterating active flag
*
* @param iteratingActive
* Iterating active true or false.
*/
@Override
public void setIteratingActive(boolean iteratingActive)
{
this.iteratingActive = iteratingActive;
}
/**
* Sets the auto-closable object, which may be set once as soon as the iterating active flag becomes true.
*
* @param iteratingActiveSegment
* Pass the auto-closable object at the instant the iterating active flag becomes true.
* Pass <code>null</code> as soon as the iterating active flag becomes false.
*/
@Override
public void setIteratingActiveSegment(AutoCloseable iteratingActiveSegment)
{
this.iteratingActiveSegment = iteratingActiveSegment;
}
/**
* Get the tail map. Create it if not present.
*
* @return {@link #tailingMap}.
*/
private Map<K, V> getOrCreateTailingMap()
{
if (tailingMap == null)
{
tailingMap = new IdentityHashMap<>(4);
}
return tailingMap;
}
}