/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.hp.hpl.jena.sparql.path.eval;
import java.util.ArrayList ;
import java.util.Collection ;
import java.util.HashSet ;
import java.util.Iterator ;
import java.util.Set ;
import org.apache.jena.atlas.iterator.Iter ;
import com.hp.hpl.jena.graph.Graph ;
import com.hp.hpl.jena.graph.Node ;
import com.hp.hpl.jena.sparql.path.P_FixedLength ;
import com.hp.hpl.jena.sparql.path.P_Mod ;
import com.hp.hpl.jena.sparql.path.P_NegPropSet ;
import com.hp.hpl.jena.sparql.path.Path ;
// ----
/** Path evaluator that produces duplicates.
* This is NOT SPARQL semantics.
* This class exists for experimentation.
* It is written to get the right results - not necessarily with maximum efficiency.
*/
final class PathEngineN extends PathEngine
{
private final Graph graph ;
private boolean forwardMode ;
public PathEngineN(Graph graph, boolean forward)
{
this.graph = graph ;
this.forwardMode = forward ;
}
@Override
protected Collection<Node> collector() { return new ArrayList<Node>() ; }
@Override
protected void flipDirection()
{ forwardMode = ! forwardMode ; }
@Override
protected boolean direction()
{ return forwardMode ; }
@Override
protected void doNegatedPropertySet(P_NegPropSet pathNotOneOf, Node node, Collection<Node> output)
{
// X !(:a|:b|^:c|^:d) Y = { X !(:a|:b) Y } UNION { Y !(:c|:d) X }
if ( pathNotOneOf.getFwdNodes().size() > 0 )
{
Iterator<Node> nodes1 = stepExcludeForwards(graph, node, pathNotOneOf.getFwdNodes()) ;
fill(nodes1, output) ;
}
if ( pathNotOneOf.getBwdNodes().size() > 0 )
{
Iterator<Node> nodes2 = stepExcludeBackwards(graph, node, pathNotOneOf.getBwdNodes()) ;
fill(nodes2, output) ;
}
}
@Override
protected void doAlt(Path pathStepLeft, Path pathStepRight, Node node, Collection<Node> output)
{
// Try both sizes, accumulate into output.
Iterator<Node> iter = eval(graph, pathStepLeft, node) ;
fill(iter, output) ;
iter = eval(graph, pathStepRight, node) ;
fill(iter, output) ;
}
@Override
protected void doSeq(Path pathStepLeft, Path pathStepRight, Node node, Collection<Node> output)
{
Path part1 = forwardMode ? pathStepLeft : pathStepRight ;
Path part2 = forwardMode ? pathStepRight : pathStepLeft ;
// Feed one side into the other
Iter<Node> iter = eval(graph, part1, node) ;
for ( Node n : iter )
eval(graph, part2, n, output) ;
}
@Override
protected void doMultiLengthPath(Path pathStep, Node node, long min1, long max1, Collection<Node> output)
{
// Why not always reduce {N,M} to {N} and {0,M-N}
// Why not iterate, not recurse, for {N,}
// -- optimizer wil have expanded this so only in unoptimized mode.
if ( min1 == P_Mod.UNSET )
// {,N}
min1 = 0 ;
// ----------------
// This code is for p{n,m} and :p{,n} inc :p{0,n}
// and for :p{N,}
//if ( max1 == P_Mod.UNSET ) max1 = 0 ;
if ( min1 == 0 )
output.add(node) ;
if ( max1 == 0 )
return ;
// The next step
long min2 = dec(min1) ;
long max2 = dec(max1) ;
// TODO Rewrite
Path p1 = pathStep ;
Path p2 = new P_Mod(pathStep, min2, max2) ;
if ( !forwardMode )
{
// Reverse order. Do the second bit first.
Path tmp = p1 ;
p1 = p2 ; p2 = tmp ;
// This forces execution to be in the order that it's written, when working backwards.
// {N,*} is {*} then {N} backwards != do {N} then do {*} as cardinality of the
// two operations is different.
}
// ****
// One step.
Iterator<Node> iter = eval(graph, p1, node) ;
// Moved on one step
for ( ; iter.hasNext() ; )
{
Node n2 = iter.next() ;
Iterator<Node> iter2 = eval(graph, p2, n2) ;
fill(iter2, output) ;
}
// If no matches, will not call eval and we drop out.
}
@Override
protected void doFixedLengthPath(Path pathStep, Node node, long fixedLength, Collection<Node> output)
{
if ( fixedLength == 0 )
{
output.add(node) ;
return ;
}
// P_Mod(path, count, count)
// One step.
Iterator<Node> iter = eval(graph, pathStep, node) ;
// Build a path for all remaining steps.
long count2 = dec(fixedLength) ;
P_FixedLength nextPath = new P_FixedLength(pathStep, count2) ;
// For each element in the first step, do remaining step
// Accumulate across everything from first step.
for ( ; iter.hasNext() ; )
{
Node n2 = iter.next() ;
Iterator<Node> iter2 = eval(graph, nextPath, n2) ;
fill(iter2, output) ;
}
}
@Override
protected void doZeroOrOne(Path pathStep, Node node, Collection<Node> output)
{
doZero(pathStep, node, output) ;
doOne(pathStep, node, output) ;
}
private void doOne(Path path, Node node, Collection<Node> output)
{
Iterator<Node> iter = eval(graph, path, node) ;
fill(iter, output) ;
}
@Override
protected void doZero(Path path, Node node, Collection<Node> output)
{
output.add(node) ;
}
@Override
protected void doZeroOrMore(Path path, Node node, Collection<Node> output)
{
Set<Node> visited = new HashSet<Node>() ;
ALP(node, path, visited, output) ;
}
@Override
protected void doOneOrMore(Path path, Node node, Collection<Node> output)
{
Set<Node> visited = new HashSet<Node>() ;
// Do one step without including.
Iterator<Node> iter1 = eval(graph, path, node) ;
for ( ; iter1.hasNext() ; )
{
Node n1 = iter1.next();
ALP(n1, path, visited, output) ;
}
}
// This is the worker function for path*
private void ALP(Node node, Path path, Collection<Node> visited, Collection<Node> output)
{
if ( visited.contains(node) ) return ;
// If output is a set, then no point going on if node has been added to the results.
// If output includes duplicates, more solutions are generated
// "visited" is nodes on this path (see the matching .remove).
if ( ! output.add(node) )
return ;
visited.add(node) ;
Iterator<Node> iter1 = eval(graph, path, node) ;
// For each step, add to results and recurse.
for ( ; iter1.hasNext() ; )
{
Node n1 = iter1.next();
ALP(n1, path, visited, output) ;
}
visited.remove(node) ;
}
}