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/*******************************************************************************
* Copyright (c) 2009, 2017 Cloudsmith Inc. and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* Cloudsmith Inc. - initial API and implementation
*******************************************************************************/
package org.eclipse.equinox.internal.p2.metadata.expression;
import java.lang.reflect.Array;
import java.util.*;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.equinox.p2.metadata.index.IIndexProvider;
import org.eclipse.equinox.p2.query.IQuery;
import org.eclipse.equinox.p2.query.IQueryResult;
/**
* A result optimized for dealing with iterators returned from
* expression evaluation.
*/
public class QueryResult<T> implements IQueryResult<T> {
private final IRepeatableIterator<T> iterator;
private boolean firstUse = true;
/**
* Create an QueryResult based on the given iterator. The <code>oneShot</code> parameter
* can be set to <code>true</code> if the returned instance is expected to be perused
* only once. This will allow some optimizations since the result of the iteration doesn't
* need to be copied in preparation for a second iteration.
*
* @param iterator The iterator to use as the result iterator.
*/
public QueryResult(Iterator<T> iterator) {
this.iterator = (iterator instanceof IRepeatableIterator<?>) ? (IRepeatableIterator<T>) iterator : RepeatableIterator.create(iterator);
}
public QueryResult(Collection<T> collection) {
this.iterator = RepeatableIterator.create(collection);
}
@Override
public boolean isEmpty() {
return !iterator.hasNext();
}
@Override
public Iterator<T> iterator() {
if (firstUse) {
firstUse = false;
return iterator;
}
return iterator.getCopy();
}
@Override
@SuppressWarnings("unchecked")
public T[] toArray(Class<T> clazz) {
Object provider = iterator.getIteratorProvider();
if (provider.getClass().isArray())
return (T[]) provider;
Collection<T> c = toUnmodifiableSet();
return c.toArray((T[]) Array.newInstance(clazz, c.size()));
}
@Override
@SuppressWarnings("unchecked")
public Set<T> toSet() {
Object provider = iterator.getIteratorProvider();
if (provider instanceof Collection<?>)
return new HashSet<>((Collection<T>) provider);
if (provider instanceof IIndexProvider<?>)
return iteratorToSet(((IIndexProvider<T>) provider).everything());
if (provider.getClass().isArray()) {
T[] elems = (T[]) provider;
int idx = elems.length;
HashSet<T> copy = new HashSet<>(idx);
while (--idx >= 0)
copy.add(elems[idx]);
return copy;
}
if (provider instanceof Map<?, ?>)
return new HashSet<>((Set<T>) ((Map<?, ?>) provider).entrySet());
return iteratorToSet(iterator());
}
@Override
public IQueryResult<T> query(IQuery<T> query, IProgressMonitor monitor) {
return query.perform(iterator());
}
@Override
@SuppressWarnings("unchecked")
public Set<T> toUnmodifiableSet() {
Object provider = iterator.getIteratorProvider();
if (provider instanceof Set<?>)
return Collections.unmodifiableSet((Set<T>) provider);
if (provider instanceof Map<?, ?>)
return Collections.unmodifiableSet((Set<T>) ((Map<?, ?>) provider).entrySet());
return toSet();
}
private Set<T> iteratorToSet(Iterator<T> iter) {
HashSet<T> set = new HashSet<>();
while (iter.hasNext())
set.add(iter.next());
return set;
}
}
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