| using System; |
| using Lucene.Net.Analysis.TokenAttributes; |
| using Lucene.Net.Util; |
| |
| namespace Lucene.Net.Analysis.Miscellaneous |
| { |
| /* |
| * 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. |
| */ |
| |
| /// <summary> |
| /// Trims leading and trailing whitespace from Tokens in the stream. |
| /// <para>As of Lucene 4.4, this filter does not support updateOffsets=true anymore |
| /// as it can lead to broken token streams. |
| /// </para> |
| /// </summary> |
| public sealed class TrimFilter : TokenFilter |
| { |
| private readonly bool updateOffsets; |
| private readonly ICharTermAttribute termAtt; |
| private readonly IOffsetAttribute offsetAtt; |
| |
| /// <summary> |
| /// Create a new <see cref="TrimFilter"/>. </summary> |
| /// <param name="version"> the Lucene match version </param> |
| /// <param name="in"> the stream to consume </param> |
| /// <param name="updateOffsets"> whether to update offsets </param> |
| /// @deprecated Offset updates are not supported anymore as of Lucene 4.4. |
| [Obsolete("Offset updates are not supported anymore as of Lucene 4.4.")] |
| public TrimFilter(LuceneVersion version, TokenStream @in, bool updateOffsets) |
| : base(@in) |
| { |
| if (updateOffsets && version.OnOrAfter(LuceneVersion.LUCENE_44)) |
| { |
| throw new ArgumentException("updateOffsets=true is not supported anymore as of Lucene 4.4"); |
| } |
| termAtt = AddAttribute<ICharTermAttribute>(); |
| offsetAtt = AddAttribute<IOffsetAttribute>(); |
| this.updateOffsets = updateOffsets; |
| } |
| |
| /// <summary> |
| /// Create a new <see cref="TrimFilter"/> on top of <paramref name="in"/>. </summary> |
| public TrimFilter(LuceneVersion version, TokenStream @in) |
| #pragma warning disable 612, 618 |
| : this(version, @in, false) |
| #pragma warning restore 612, 618 |
| { |
| } |
| |
| public override bool IncrementToken() |
| { |
| if (!m_input.IncrementToken()) |
| { |
| return false; |
| } |
| |
| char[] termBuffer = termAtt.Buffer; |
| int len = termAtt.Length; |
| //TODO: Is this the right behavior or should we return false? Currently, " ", returns true, so I think this should |
| //also return true |
| if (len == 0) |
| { |
| return true; |
| } |
| int start = 0; |
| int end = 0; |
| int endOff = 0; |
| |
| // eat the first characters |
| for (start = 0; start < len && char.IsWhiteSpace(termBuffer[start]); start++) |
| { |
| } |
| // eat the end characters |
| for (end = len; end >= start && char.IsWhiteSpace(termBuffer[end - 1]); end--) |
| { |
| endOff++; |
| } |
| if (start > 0 || end < len) |
| { |
| if (start < end) |
| { |
| termAtt.CopyBuffer(termBuffer, start, (end - start)); |
| } |
| else |
| { |
| termAtt.SetEmpty(); |
| } |
| if (updateOffsets && len == offsetAtt.EndOffset - offsetAtt.StartOffset) |
| { |
| int newStart = offsetAtt.StartOffset + start; |
| int newEnd = offsetAtt.EndOffset - (start < end ? endOff : 0); |
| offsetAtt.SetOffset(newStart, newEnd); |
| } |
| } |
| |
| return true; |
| } |
| } |
| } |