1 files changed, 54 insertions, 0 deletions
diff --git a/src/core/Search/Filter.cs b/src/core/Search/Filter.cs
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+/* 
+ * 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.
+ */
+
+using System;
+
+using IndexReader = Lucene.Net.Index.IndexReader;
+using DocIdBitSet = Lucene.Net.Util.DocIdBitSet;
+
+namespace Lucene.Net.Search
+{
+	
+	/// <summary>Abstract base class for restricting which documents may be returned during searching.</summary>
+	[Serializable]
+	public abstract class Filter
+	{
+	    ///<summary>
+	    ///  <para>Creates a <see cref="DocIdSet" /> enumerating the documents that should be
+	    ///  permitted in search results. <b>NOTE:</b> null can be
+	    ///  returned if no documents are accepted by this Filter.</para>
+	    ///  <p/>
+	    ///  <para>Note: This method will be called once per segment in
+	    ///  the index during searching.  The returned <see cref="DocIdSet" />
+	    ///  must refer to document IDs for that segment, not for
+	    ///  the top-level reader.</para>
+	    ///</summary>
+	    /// <returns> a DocIdSet that provides the documents which should be permitted or
+	    /// prohibited in search results. <b>NOTE:</b> null can be returned if
+	    /// no documents will be accepted by this Filter.
+	    /// </returns>
+	    /// <param name="reader">
+	    /// A <see cref="IndexReader" /> instance opened on the index currently
+	    /// searched on. Note, it is likely that the provided reader does not
+	    /// represent the whole underlying index i.e. if the index has more than
+	    /// one segment the given reader only represents a single segment.
+	    /// </param>
+	    /// <seealso cref="DocIdBitSet">
+	    /// </seealso>
+	    public abstract DocIdSet GetDocIdSet(IndexReader reader);
+	}
+}
+\ No newline at end of file