/*******************************************************************************
* Copyright 2014 Analog Devices, Inc.
*
* 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 com.analog.lyric.dimple.model.domains;
import org.eclipse.jdt.annotation.Nullable;
import com.analog.lyric.collect.WeakInterner;
import com.analog.lyric.math.Utilities;
import com.google.common.collect.Interner;
import net.jcip.annotations.Immutable;
/**
* A finite field of characteristic 2 (GF(2<sup>N</sup>)). The domain is determined by the length, N,
* as well as the primitive polynomial.
*/
@Immutable
public class FiniteFieldDomain extends TypedDiscreteDomain<FiniteFieldNumber>
{
private static final long serialVersionUID = 1L;
private int _primitivePolynomial;
private int _N;
private int _size;
private static enum InternedDomains
{
INSTANCE;
private final Interner<FiniteFieldDomain> interner = WeakInterner.create();
}
/*--------------
* Construction
*/
/**
* Create finite field domain with specified primitive polynomial.
* @since 0.07
*/
public static FiniteFieldDomain create(int primitivePolynomial)
{
return new FiniteFieldDomain(primitivePolynomial).intern();
}
FiniteFieldDomain(int primitivePolynomial)
{
super(computeHashCode(primitivePolynomial));
_primitivePolynomial = primitivePolynomial;
_N = Utilities.findMSB(primitivePolynomial) - 1;
_size = 1 << _N;
}
private static int computeHashCode(int primitivePolynomial)
{
return primitivePolynomial;
}
@Override
protected FiniteFieldDomain intern()
{
return InternedDomains.INSTANCE.interner.intern(this);
}
public final int getPrimitivePolynomial()
{
return _primitivePolynomial;
}
public int getN()
{
return _N;
}
/*----------------
* Object methods
*/
@Override
public final boolean equals(@Nullable Object that)
{
if (this == that)
return true;
if (that instanceof FiniteFieldDomain)
{
FiniteFieldDomain thatFF = (FiniteFieldDomain)that;
return _primitivePolynomial == thatFF._primitivePolynomial;
}
return false;
}
/*------------------------
* DiscreteDomain methods
*/
@Override
public final int size()
{
return _size;
}
/*------------------------
* TypedDiscreteDomain methods
*/
@Override
public final FiniteFieldNumber getElement(int i)
{
assertIndexInBounds(i, _size);
return new FiniteFieldNumber(i, this);
}
@Override
public final Class<FiniteFieldNumber> getElementClass()
{
return FiniteFieldNumber.class;
}
@Override
public final int getIndex(@Nullable Object value)
{
if (value instanceof FiniteFieldNumber)
return ((FiniteFieldNumber)value).intValue();
else if (value instanceof Integer)
return (Integer)value; // Already an index
else
return -1;
}
/*----------------
* Domain methods
*/
@Override
public boolean hasIntCompatibleValues()
{
return true;
}
@Override
public boolean isIntegral()
{
return true;
}
}