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RDF model implementations.
/*******************************************************************************
* Copyright (c) 2015 Eclipse RDF4J contributors, Aduna, and others.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Distribution License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*******************************************************************************/
package org.eclipse.rdf4j.model.impl;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import org.eclipse.rdf4j.model.IRI;
import org.eclipse.rdf4j.model.Model;
import org.eclipse.rdf4j.model.Namespace;
import org.eclipse.rdf4j.model.Resource;
import org.eclipse.rdf4j.model.Statement;
import org.eclipse.rdf4j.model.Value;
import org.eclipse.rdf4j.model.util.PatternIterator;
/**
* Hash table based implementation of the {@link Model} interface.
*
* This implementation provides constant-time performance for filters using a single term, assuming the hash function
* disperses the elements properly among the buckets. Each term is indexed using a {@link HashMap}. When multiple terms
* are provided in a filter the index, of the term that reduces the possible {@link Statement}s the most, is used and a
* sequential scan is used to filter additional terms.
*
* Note that this implementation is not synchronized. If multiple threads access a model concurrently, and at
* least one of the threads modifies the model, it must be synchronized externally. This is typically accomplished by
* synchronizing on some object that naturally encapsulates the model. If no such object exists, the set should be
* "wrapped" using the * Models.synchronizedModel method.
*
*
* @author James Leigh
*/
@SuppressWarnings("unchecked")
public class LinkedHashModel extends AbstractModel {
private static final long serialVersionUID = -9161104123818983614L;
static final Resource[] NULL_CTX = new Resource[] { null };
final Set namespaces = new LinkedHashSet<>();
transient Map values;
transient Set statements;
public LinkedHashModel() {
this(128);
}
public LinkedHashModel(Model model) {
this(model.getNamespaces());
addAll(model);
}
public LinkedHashModel(Collection c) {
this(c.size());
addAll(c);
}
public LinkedHashModel(int size) {
super();
// assume fewer unique values than statements (eg. some reuse of nodes instatements)
values = new HashMap<>(size, 0.75f);
// compensate for the loadfactor by multiplying by 2
statements = new LinkedHashSet<>(size * 2, 0.75f);
}
public LinkedHashModel(Set namespaces, Collection c) {
this(c);
this.namespaces.addAll(namespaces);
}
public LinkedHashModel(Set namespaces) {
this();
this.namespaces.addAll(namespaces);
}
public LinkedHashModel(Set namespaces, int size) {
this(size);
this.namespaces.addAll(namespaces);
}
@Override
public Optional getNamespace(String prefix) {
for (Namespace nextNamespace : namespaces) {
if (prefix.equals(nextNamespace.getPrefix())) {
return Optional.of(nextNamespace);
}
}
return Optional.empty();
}
@Override
public Set getNamespaces() {
return namespaces;
}
@Override
public Namespace setNamespace(String prefix, String name) {
removeNamespace(prefix);
Namespace result = new SimpleNamespace(prefix, name);
namespaces.add(result);
return result;
}
@Override
public void setNamespace(Namespace namespace) {
removeNamespace(namespace.getPrefix());
namespaces.add(namespace);
}
@Override
public Optional removeNamespace(String prefix) {
Optional result = getNamespace(prefix);
result.ifPresent(namespace -> namespaces.remove(namespace));
return result;
}
@Override
public int size() {
return statements.size();
}
@Override
public boolean add(Statement statement) {
Resource subj = statement.getSubject();
IRI pred = statement.getPredicate();
Value obj = statement.getObject();
Resource context = statement.getContext();
ModelNode s = asNode(subj);
ModelNode p = asNode(pred);
ModelNode o = asNode(obj);
ModelNode c = asNode(context);
ModelStatement modelStatement = new ModelStatement(s, p, o, c, statement);
return addModelStatement(modelStatement);
}
@Override
public boolean add(Resource subj, IRI pred, Value obj, Resource... contexts) {
if (subj == null || pred == null || obj == null) {
throw new UnsupportedOperationException("Incomplete statement");
}
Value[] ctxs = notNull(contexts);
if (ctxs.length == 0) {
ctxs = NULL_CTX;
}
boolean changed = false;
for (Value ctx : ctxs) {
ModelNode s = asNode(subj);
ModelNode p = asNode(pred);
ModelNode o = asNode(obj);
ModelNode c = asNode((Resource) ctx);
ModelStatement st = new ModelStatement(s, p, o, c);
changed |= addModelStatement(st);
}
return changed;
}
@Override
public void clear() {
values.clear();
statements.clear();
}
@Override
public boolean contains(Object o) {
if (o instanceof Statement) {
if (o instanceof ModelStatement) {
return statements.contains(o);
}
return find((Statement) o).hasNext();
}
return false;
}
@Override
public Iterator iterator() {
return matchPattern(null, null, null);
}
@Override
public boolean contains(Resource subj, IRI pred, Value obj, Resource... contexts) {
return matchPattern(subj, pred, obj, contexts).hasNext();
}
@Override
public boolean remove(Resource subj, IRI pred, Value obj, Resource... contexts) {
if (isEmpty()) {
return false;
}
Iterator iter = matchPattern(subj, pred, obj, contexts);
if (!iter.hasNext()) {
return false;
}
while (iter.hasNext()) {
iter.next();
iter.remove();
}
return true;
}
@Override
public Model filter(final Resource subj, final IRI pred, final Value obj, final Resource... contexts) {
return new FilteredModel(this, subj, pred, obj, contexts) {
private static final long serialVersionUID = 396293781006255959L;
@Override
public Iterator iterator() {
return matchPattern(subj, pred, obj, contexts);
}
@Override
protected void removeFilteredTermIteration(Iterator iter, Resource subj, IRI pred, Value obj,
Resource... contexts) {
LinkedHashModel.this.removeTermIteration(iter, subj, pred, obj, contexts);
}
};
}
@Override
public void removeTermIteration(Iterator iterator, Resource subj, IRI pred, Value obj, Resource... contexts) {
Set owner = ((ModelIterator) iterator).getOwner();
Set chosen = choose(subj, pred, obj, contexts);
Iterator iter = chosen.iterator();
iter = new PatternIterator<>(iter, subj, pred, obj, contexts);
while (iter.hasNext()) {
ModelStatement last = iter.next();
if (statements == owner) {
statements = new LinkedHashSet<>(statements);
statements.remove(last);
} else if (statements != chosen) {
statements.remove(last);
}
if (last.subj.subjects == owner) {
last.subj.subjects = new LinkedHashSet<>(last.subj.subjects);
last.subj.subjects.remove(last);
} else if (last.subj.subjects != chosen) {
last.subj.subjects.remove(last);
}
if (last.pred.predicates == owner) {
last.pred.predicates = new LinkedHashSet<>(statements);
last.pred.predicates.remove(last);
} else if (last.pred.predicates != chosen) {
last.pred.predicates.remove(last);
}
if (last.obj.objects == owner) {
last.obj.objects = new LinkedHashSet<>(statements);
last.obj.objects.remove(last);
} else if (last.obj.objects != chosen) {
last.obj.objects.remove(last);
}
if (last.ctx.contexts == owner) {
last.ctx.contexts = new LinkedHashSet<>(statements);
last.ctx.contexts.remove(last);
} else if (last.ctx.contexts != chosen) {
last.ctx.contexts.remove(last);
}
if (owner != chosen) {
iter.remove(); // remove from chosen
}
}
}
@Override
public boolean isEmpty() {
return statements.isEmpty();
}
private class ModelIterator implements Iterator {
private final Iterator iter;
private final Set owner;
private ModelStatement last;
public ModelIterator(Iterator iter, Set owner) {
this.iter = iter;
this.owner = owner;
}
public Set getOwner() {
return owner;
}
@Override
public boolean hasNext() {
return iter.hasNext();
}
@Override
public ModelStatement next() {
return last = iter.next();
}
@Override
public void remove() {
if (last == null) {
throw new IllegalStateException();
}
removeFrom(statements);
removeFrom(last.subj.subjects);
removeFrom(last.pred.predicates);
removeFrom(last.obj.objects);
removeFrom(last.ctx.contexts);
iter.remove(); // remove from owner
}
private void removeFrom(Set subjects) {
if (subjects != owner) {
subjects.remove(last);
}
}
}
private static class ModelNode implements Serializable {
private static final long serialVersionUID = -1205676084606998540L;
Set subjects = new LinkedHashSet<>();
Set predicates = new LinkedHashSet<>();
Set objects = new LinkedHashSet<>();
Set contexts = new LinkedHashSet<>();
private final V value;
public ModelNode(V value) {
this.value = value;
}
public V getValue() {
return value;
}
}
public static class ModelStatement extends GenericStatement {
private static final long serialVersionUID = 2200404772364346279L;
private Statement statement;
ModelNode subj;
ModelNode pred;
ModelNode obj;
ModelNode ctx;
ModelStatement(ModelNode subj, ModelNode pred, ModelNode obj,
ModelNode ctx) {
super(subj.getValue(), pred.getValue(), obj.getValue(), ctx.getValue());
this.subj = subj;
this.pred = pred;
this.obj = obj;
this.ctx = ctx;
}
ModelStatement(ModelNode subj, ModelNode pred, ModelNode obj,
ModelNode ctx, Statement statement) {
super(subj.getValue(), pred.getValue(), obj.getValue(), ctx.getValue());
this.subj = subj;
this.pred = pred;
this.obj = obj;
this.ctx = ctx;
this.statement = statement;
}
@Override
public Resource getSubject() {
return subj.getValue();
}
@Override
public IRI getPredicate() {
return pred.getValue();
}
@Override
public Value getObject() {
return obj.getValue();
}
@Override
public Resource getContext() {
if (ctx == null) {
return null;
}
return ctx.getValue();
}
@Override
public boolean equals(Object other) {
if (this == other) {
return true;
}
if (!super.equals(other)) {
return false;
}
if (getContext() == null) {
return ((Statement) other).getContext() == null;
}
return getContext().equals(((Statement) other).getContext());
}
public Statement getStatement() {
return statement;
}
}
private void writeObject(ObjectOutputStream s) throws IOException {
// Write out any hidden serialization magic
s.defaultWriteObject();
// Write in size
s.writeInt(statements.size());
// Write in all elements
for (ModelStatement st : statements) {
Resource subj = st.getSubject();
IRI pred = st.getPredicate();
Value obj = st.getObject();
Resource ctx = st.getContext();
s.writeObject(new GenericStatement<>(subj, pred, obj, ctx));
}
}
private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
// Read in any hidden serialization magic
s.defaultReadObject();
// Read in size
int size = s.readInt();
values = new HashMap<>(size * 2);
statements = new LinkedHashSet<>(size);
// Read in all elements
for (int i = 0; i < size; i++) {
Statement st = (Statement) s.readObject();
add(st);
}
}
private ModelIterator matchPattern(Resource subj, IRI pred, Value obj, Resource... contexts) {
Set set = choose(subj, pred, obj, contexts);
Iterator it = set.iterator();
Iterator iter;
iter = new PatternIterator<>(it, subj, pred, obj, contexts);
return new ModelIterator(iter, set);
}
private Set choose(Resource subj, IRI pred, Value obj, Resource... contexts) {
contexts = notNull(contexts);
Set s = null;
Set p = null;
Set o = null;
if (subj != null) {
ModelNode modelNode = values.get(subj);
if (modelNode == null) {
return Collections.emptySet();
}
s = modelNode.subjects;
}
if (pred != null) {
ModelNode modelNode = values.get(pred);
if (modelNode == null) {
return Collections.emptySet();
}
p = modelNode.predicates;
}
if (obj != null) {
ModelNode modelNode = values.get(obj);
if (modelNode == null) {
return Collections.emptySet();
}
o = modelNode.objects;
}
if (contexts.length == 1) {
ModelNode modelNode = values.get(contexts[0]);
if (modelNode == null) {
return Collections.emptySet();
}
Set c = modelNode.contexts;
return smallest(statements, s, p, o, c);
} else {
return smallest(statements, s, p, o);
}
}
private Resource[] notNull(Resource[] contexts) {
if (contexts == null) {
return new Resource[] { null };
}
return contexts;
}
private Iterator find(Statement st) {
Resource subj = st.getSubject();
IRI pred = st.getPredicate();
Value obj = st.getObject();
Resource ctx = st.getContext();
return matchPattern(subj, pred, obj, ctx);
}
private boolean addModelStatement(ModelStatement st) {
Set subj = st.subj.subjects;
Set pred = st.pred.predicates;
Set obj = st.obj.objects;
Set ctx = st.ctx.contexts;
if (smallest(subj, pred, obj, ctx).contains(st)) {
return false;
}
statements.add(st);
subj.add(st);
pred.add(st);
obj.add(st);
ctx.add(st);
return true;
}
private Set smallest(Set... sets) {
int minSize = Integer.MAX_VALUE;
Set minSet = null;
for (Set set : sets) {
if (set != null && set.size() < minSize) {
minSet = set;
minSize = set.size();
}
}
return minSet;
}
private ModelNode asNode(V value) {
ModelNode node = values.get(value);
if (node != null) {
return node;
}
node = new ModelNode<>(value);
values.put(value, node);
return node;
}
}