gnu.trove.TByteHash Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of trove4j Show documentation
Show all versions of trove4j Show documentation
The Trove library provides high speed regular and primitive
collections for Java.
///////////////////////////////////////////////////////////////////////////////
// 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;
//////////////////////////////////////////////////
// THIS IS A GENERATED CLASS. DO NOT HAND EDIT! //
//////////////////////////////////////////////////
/**
* An open addressed hashing implementation for byte primitives.
*
* Created: Sun Nov 4 08:56:06 2001
*
* @author Eric D. Friedman
* @version $Id: PHash.template,v 1.2 2007/06/29 22:39:46 robeden Exp $
*/
abstract public class TByteHash extends TPrimitiveHash implements TByteHashingStrategy {
/** the set of bytes */
protected transient byte[] _set;
/** strategy used to hash values in this collection */
protected TByteHashingStrategy _hashingStrategy;
/**
* Creates a new TByteHash instance with the default
* capacity and load factor.
*/
public TByteHash() {
super();
this._hashingStrategy = this;
}
/**
* Creates a new TByteHash instance whose capacity
* is the next highest prime above initialCapacity + 1
* unless that value is already prime.
*
* @param initialCapacity an int value
*/
public TByteHash(int initialCapacity) {
super(initialCapacity);
this._hashingStrategy = this;
}
/**
* Creates a new TByteHash instance with a prime
* value at or near the specified capacity and load factor.
*
* @param initialCapacity used to find a prime capacity for the table.
* @param loadFactor used to calculate the threshold over which
* rehashing takes place.
*/
public TByteHash(int initialCapacity, float loadFactor) {
super(initialCapacity, loadFactor);
this._hashingStrategy = this;
}
/**
* Creates a new TByteHash instance with the default
* capacity and load factor.
* @param strategy used to compute hash codes and to compare keys.
*/
public TByteHash(TByteHashingStrategy strategy) {
super();
this._hashingStrategy = strategy;
}
/**
* Creates a new TByteHash instance whose capacity
* is the next highest prime above initialCapacity + 1
* unless that value is already prime.
*
* @param initialCapacity an int value
* @param strategy used to compute hash codes and to compare keys.
*/
public TByteHash(int initialCapacity, TByteHashingStrategy strategy) {
super(initialCapacity);
this._hashingStrategy = strategy;
}
/**
* Creates a new TByteHash instance with a prime
* value at or near the specified capacity and load factor.
*
* @param initialCapacity used to find a prime capacity for the table.
* @param loadFactor used to calculate the threshold over which
* rehashing takes place.
* @param strategy used to compute hash codes and to compare keys.
*/
public TByteHash(int initialCapacity, float loadFactor, TByteHashingStrategy strategy) {
super(initialCapacity, loadFactor);
this._hashingStrategy = strategy;
}
/**
* @return a deep clone of this collection
*/
public Object clone() {
TByteHash h = (TByteHash)super.clone();
h._set = (byte[])this._set.clone();
return h;
}
/**
* 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);
_set = new byte[capacity];
return capacity;
}
/**
* Searches the set for val
*
* @param val an byte value
* @return a boolean value
*/
public boolean contains(byte val) {
return index(val) >= 0;
}
/**
* Executes procedure for each element in the set.
*
* @param procedure a TObjectProcedure value
* @return false if the loop over the set terminated because
* the procedure returned false for some value.
*/
public boolean forEach(TByteProcedure procedure) {
byte[] states = _states;
byte[] set = _set;
for (int i = set.length; i-- > 0;) {
if (states[i] == FULL && ! procedure.execute(set[i])) {
return false;
}
}
return true;
}
/**
* Releases the element currently stored at index.
*
* @param index an int value
*/
protected void removeAt(int index) {
_set[index] = (byte)0;
super.removeAt(index);
}
/**
* Locates the index of val.
*
* @param val an byte value
* @return the index of val or -1 if it isn't in the set.
*/
protected int index(byte val) {
int hash, probe, index, length;
final byte[] states = _states;
final byte[] set = _set;
length = states.length;
hash = _hashingStrategy.computeHashCode(val) & 0x7fffffff;
index = hash % length;
if (states[index] != FREE &&
(states[index] == REMOVED || set[index] != val)) {
// see Knuth, p. 529
probe = 1 + (hash % (length - 2));
do {
index -= probe;
if (index < 0) {
index += length;
}
} while (states[index] != FREE &&
(states[index] == REMOVED || set[index] != val));
}
return states[index] == FREE ? -1 : index;
}
/**
* Locates the index at which val can be inserted. if
* there is already a value equal()ing val in the set,
* returns that value as a negative integer.
*
* @param val an byte value
* @return an int value
*/
protected int insertionIndex(byte val) {
int hash, probe, index, length;
final byte[] states = _states;
final byte[] set = _set;
length = states.length;
hash = _hashingStrategy.computeHashCode(val) & 0x7fffffff;
index = hash % length;
if (states[index] == FREE) {
return index; // empty, all done
} else if (states[index] == FULL && set[index] == val) {
return -index -1; // already stored
} else { // already FULL or REMOVED, must probe
// compute the double hash
probe = 1 + (hash % (length - 2));
// if the slot we landed on is FULL (but not removed), probe
// until we find an empty slot, a REMOVED slot, or an element
// equal to the one we are trying to insert.
// finding an empty slot means that the value is not present
// and that we should use that slot as the insertion point;
// finding a REMOVED slot means that we need to keep searching,
// however we want to remember the offset of that REMOVED slot
// so we can reuse it in case a "new" insertion (i.e. not an update)
// is possible.
// finding a matching value means that we've found that our desired
// key is already in the table
if (states[index] != REMOVED) {
// starting at the natural offset, probe until we find an
// offset that isn't full.
do {
index -= probe;
if (index < 0) {
index += length;
}
} while (states[index] == FULL && set[index] != val);
}
// if the index we found was removed: continue probing until we
// locate a free location or an element which equal()s the
// one we have.
if (states[index] == REMOVED) {
int firstRemoved = index;
while (states[index] != FREE &&
(states[index] == REMOVED || set[index] != val)) {
index -= probe;
if (index < 0) {
index += length;
}
}
return states[index] == FULL ? -index -1 : firstRemoved;
}
// if it's full, the key is already stored
return states[index] == FULL ? -index -1 : index;
}
}
/**
* Default implementation of TByteHashingStrategy:
* delegates hashing to HashFunctions.hash(byte).
*
* @param val the value to hash
* @return the hashcode.
*/
public final int computeHashCode(byte val) {
return HashFunctions.hash(val);
}
} // TByteHash