src/Lucene.Net/Search/PrefixTermsEnum.cs

namespace Lucene.Net.Search
{
    /*
     * 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 BytesRef = Lucene.Net.Util.BytesRef;
    using FilteredTermsEnum = Lucene.Net.Index.FilteredTermsEnum;
    using StringHelper = Lucene.Net.Util.StringHelper;
    using TermsEnum = Lucene.Net.Index.TermsEnum;

    /// <summary>
    /// Subclass of <see cref="FilteredTermsEnum"/> for enumerating all terms that match the
    /// specified prefix filter term.
    /// <para>Term enumerations are always ordered by
    /// <see cref="TermsEnum.Comparer"/>.  Each term in the enumeration is
    /// greater than all that precede it.</para>
    /// </summary>
    public class PrefixTermsEnum : FilteredTermsEnum
    {
        private readonly BytesRef prefixRef;

        public PrefixTermsEnum(TermsEnum tenum, BytesRef prefixText)
            : base(tenum)
        {
            SetInitialSeekTerm(this.prefixRef = prefixText);
        }

        protected override AcceptStatus Accept(BytesRef term)
        {
            if (StringHelper.StartsWith(term, prefixRef))
            {
                return AcceptStatus.YES;
            }
            else
            {
                return AcceptStatus.END;
            }
        }
    }
}