1 files changed, 57 insertions, 0 deletions
diff --git a/bundles/org.eclipse.equinox.p2.metadata/src/org/eclipse/equinox/p2/query/LimitQuery.java b/bundles/org.eclipse.equinox.p2.metadata/src/org/eclipse/equinox/p2/query/LimitQuery.java
new file mode 100644
index 000000000..6da75ca1f
--- /dev/null
+++ b/bundles/org.eclipse.equinox.p2.metadata/src/org/eclipse/equinox/p2/query/LimitQuery.java
@@ -0,0 +1,57 @@
+/******************************************************************************* 
+* Copyright (c) 2009 EclipseSource and others. All rights reserved. This
+* program and the accompanying materials are made available under the terms of
+* the Eclipse Public License v1.0 which accompanies this distribution, and is
+* available at http://www.eclipse.org/legal/epl-v10.html
+*
+* Contributors:
+*   EclipseSource - initial API and implementation
+******************************************************************************/
+package org.eclipse.equinox.p2.query;
+
+import java.util.*;
+
+/**
+ * A limit query can be used to limit the number of query results returned.  Once
+ * the limit is reached, the query is terminated.
+ * @since 2.0
+ */
+public class LimitQuery<T> extends ContextQuery<T> implements ICompositeQuery<T> {
+
+	private final IQuery<T> query;
+	private final int limit;
+
+	public LimitQuery(IQuery<T> query, int limit) {
+		this.query = query;
+		this.limit = limit;
+	}
+
+	public IQueryResult<T> perform(Iterator<T> iterator) {
+		if (limit == 0)
+			return Collector.emptyCollector();
+
+		int count = 0;
+		Collector<T> result = new Collector<T>();
+		if (query instanceof IMatchQuery<?>) {
+			IMatchQuery<T> matchQuery = (IMatchQuery<T>) query;
+			while (iterator.hasNext()) {
+				T candidate = iterator.next();
+				if (matchQuery.isMatch(candidate)) {
+					result.accept(candidate);
+					if (++count >= limit)
+						break;
+				}
+			}
+		} else {
+			iterator = query.perform(iterator).iterator();
+			while (++count <= limit && iterator.hasNext())
+				result.accept(iterator.next());
+		}
+		return result;
+	}
+
+	public List<IQuery<T>> getQueries() {
+		return Collections.singletonList(query);
+	}
+
+}