package org.drools.reteoo;
/*
* $Id: FactHandleList.java,v 1.7 2005/05/08 16:13:33 memelet Exp $
*
* Copyright 2001-2004 (C) The Werken Company. All Rights Reserved.
*
* Redistribution and use of this software and associated documentation
* ("Software"), with or without modification, are permitted provided that the
* following conditions are met:
*
* 1. Redistributions of source code must retain copyright statements and
* notices. Redistributions must also contain a copy of this document.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The name "drools" must not be used to endorse or promote products derived
* from this Software without prior written permission of The Werken Company.
* For written permission, please contact bob@werken.com.
*
* 4. Products derived from this Software may not be called "drools" nor may
* "drools" appear in their names without prior written permission of The Werken
* Company. "drools" is a trademark of The Werken Company.
*
* 5. Due credit should be given to The Werken Company. (http://werken.com/)
*
* THIS SOFTWARE IS PROVIDED BY THE WERKEN COMPANY AND CONTRIBUTORS ``AS IS''
* AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE WERKEN COMPANY OR ITS CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*/
import java.io.Serializable;
import java.util.Arrays;
import org.drools.FactHandle;
/**
* Specialised array of {@link FactHandle}s intended to be keyed by a {@link Declaration}s
* index. The list only ever contains as many elements as necessary to hold a handle at the
* position specified by the largest Declaration index. As a result, the list will neccessarily
* contain <code>NULL</code> values.
*
* This class exists purely for performance reasons and as such, many assumptions have been
* made regarding behaviour based on know usage. Therefore, this class should in no way be
* considered a general purpose data structure. Hence it resides in this package and not a more
* generic "util" package.
*
* @author <a href="mailto:simon@redhillconsulting.com.au">Simon Harris</a>
*/
final class FactHandleList implements Serializable
{
/** Empty list for testing purposes only. */
static final FactHandleList EMPTY_LIST = new FactHandleList( );
/** The list of handles. */
private final FactHandle[] handles;
/** The cached hash code value. */
private final int hashCode;
/**
* Private constructor for creating the {@link #EMPTY_LIST}.
*/
private FactHandleList()
{
handles = new FactHandleImpl[ 0 ];
hashCode = 0;
}
/**
* Join two lists.
* @param left The left list.
* @param right The right list.
*/
public FactHandleList( FactHandleList left,
FactHandleList right )
{
this.handles = new FactHandle[ Math.max( left.handles.length, right.handles.length ) ];
System.arraycopy( left.handles, 0, this.handles, 0, left.handles.length );
int hashCode = left.hashCode;
FactHandle handle;
for ( int i = right.handles.length - 1; i >= 0; i-- )
{
handle = right.handles[ i ];
if ( handle != null && this.handles[ i ] == null )
{
this.handles[ i ] = handle;
hashCode += handle.hashCode( );
}
}
this.hashCode = hashCode;
}
/**
* Single value constructor.
* @param index The index at which the handle will be placed.
* @param handle The handle to use.
*/
public FactHandleList( int index, FactHandle handle )
{
this.handles = new FactHandleImpl[ index + 1 ];
this.handles[ index ] = handle;
this.hashCode = handle.hashCode( );
}
/**
* Obtains the handle at a specified index.
* @param index The position from which the handle should be obtained.
* @return The handle; or <code>null</code> if no handle exists.
* @throws ArrayIndexOutOfBoundsException if <code>index</code> > {@link #size()}.
*/
public FactHandle get( int index )
{
return this.handles[ index ];
}
/**
* Determines if the list contains a specified handle.
* @param handle The handle to search for.
* @return <code>true</code> if the handle is found; otherwise <code>false</code>
*/
public boolean contains( FactHandle handle )
{
for ( int i = handles.length - 1; i >= 0; i-- )
{
if ( handle.equals( handles[ i ] ) )
{
return true;
}
}
return false;
}
/**
* Determines if the list is a super-set of another list.
* @param other The list to be checked.
* @return <code>true</code> if this list contains all values
* from the other list; <code>false</code> otherwise.
*/
public boolean containsAll( FactHandleList other )
{
if ( other.handles.length > this.handles.length )
{
return false;
}
FactHandle handle;
for ( int i = other.handles.length - 1; i >= 0; i-- )
{
handle = other.handles[ i ];
if ( handle != null && !handle.equals( this.handles[ i ] ) )
{
return false;
}
}
return true;
}
/**
* Obtains the length of the list.
* @return The length of the list, including all <code>null</code> values.
*/
public int size()
{
return this.handles.length;
}
public int hashCode()
{
return this.hashCode;
}
public boolean equals( Object object )
{
if ( this == object )
{
return true;
}
if ( object == null || getClass( ) != object.getClass( ) )
{
return false;
}
return Arrays.equals( this.handles, ( ( FactHandleList ) object ).handles );
}
}