gnu.trove.TPrimitiveHash Maven / Gradle / Ivy
///////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2001, Eric D. Friedman All Rights Reserved.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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 General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
///////////////////////////////////////////////////////////////////////////////
package gnu.trove;
/**
* The base class for hashtables of primitive values. Since there is
* no notion of object equality for primitives, it isn't possible to
* use a `REMOVED' object to track deletions in an open-addressed table.
* So, we have to resort to using a parallel `bookkeeping' array of bytes,
* in which flags can be set to indicate that a particular slot in the
* hash table is FREE, FULL, or REMOVED.
*
* Created: Fri Jan 11 18:55:16 2002
*
* @author Eric D. Friedman
* @version $Id: TPrimitiveHash.java,v 1.5 2008/10/08 16:39:10 robeden Exp $
*/
abstract public class TPrimitiveHash extends THash {
/** flags indicating whether each position in the hash is
* FREE, FULL, or REMOVED */
protected transient byte[] _states;
/* constants used for state flags */
/** flag indicating that a slot in the hashtable is available */
protected static final byte FREE = 0;
/** flag indicating that a slot in the hashtable is occupied */
protected static final byte FULL = 1;
/** flag indicating that the value of a slot in the hashtable
* was deleted */
protected static final byte REMOVED = 2;
/**
* Creates a new THash instance with the default
* capacity and load factor.
*/
public TPrimitiveHash() {
super();
}
/**
* Creates a new TPrimitiveHash instance with a prime
* capacity at or near the specified capacity and with the default
* load factor.
*
* @param initialCapacity an int value
*/
public TPrimitiveHash(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Creates a new TPrimitiveHash instance with a prime
* capacity at or near the minimum needed to hold
* initialCapacity elements with load factor
* loadFactor without triggering a rehash.
*
* @param initialCapacity an int value
* @param loadFactor a float value
*/
public TPrimitiveHash(int initialCapacity, float loadFactor) {
super();
_loadFactor = loadFactor;
setUp(HashFunctions.fastCeil(initialCapacity / loadFactor));
}
public Object clone() {
TPrimitiveHash h = (TPrimitiveHash)super.clone();
h._states = (byte[])this._states.clone();
return h;
}
/**
* Returns the capacity of the hash table. This is the true
* physical capacity, without adjusting for the load factor.
*
* @return the physical capacity of the hash table.
*/
protected int capacity() {
return _states.length;
}
/**
* Delete the record at index.
*
* @param index an int value
*/
protected void removeAt(int index) {
_states[index] = REMOVED;
super.removeAt(index);
}
/**
* initializes the hashtable to a prime capacity which is at least
* initialCapacity + 1.
*
* @param initialCapacity an int value
* @return the actual capacity chosen
*/
protected int setUp(int initialCapacity) {
int capacity;
capacity = super.setUp(initialCapacity);
_states = new byte[capacity];
return capacity;
}
} // TPrimitiveHash