| using Lucene.Net.Store; |
| using Lucene.Net.Support; |
| |
| namespace Lucene.Net.Codecs.Lucene3x |
| { |
| /* |
| * 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> |
| /// PreFlexRW skiplist implementation. |
| /// <para/> |
| /// @lucene.experimental |
| /// </summary> |
| public class PreFlexRWSkipListWriter : MultiLevelSkipListWriter |
| { |
| private readonly int[] lastSkipDoc; // LUCENENET: marked readonly |
| private readonly int[] lastSkipPayloadLength; // LUCENENET: marked readonly |
| private readonly long[] lastSkipFreqPointer; // LUCENENET: marked readonly |
| private readonly long[] lastSkipProxPointer; // LUCENENET: marked readonly |
| |
| private readonly IndexOutput freqOutput; // LUCENENET: marked readonly |
| private readonly IndexOutput proxOutput; // LUCENENET: marked readonly |
| |
| private int curDoc; |
| private bool curStorePayloads; |
| private int curPayloadLength; |
| private long curFreqPointer; |
| private long curProxPointer; |
| |
| public PreFlexRWSkipListWriter(int skipInterval, int numberOfSkipLevels, int docCount, IndexOutput freqOutput, IndexOutput proxOutput) |
| : base(skipInterval, numberOfSkipLevels, docCount) |
| { |
| this.freqOutput = freqOutput; |
| this.proxOutput = proxOutput; |
| |
| lastSkipDoc = new int[numberOfSkipLevels]; |
| lastSkipPayloadLength = new int[numberOfSkipLevels]; |
| lastSkipFreqPointer = new long[numberOfSkipLevels]; |
| lastSkipProxPointer = new long[numberOfSkipLevels]; |
| } |
| |
| /// <summary> |
| /// Sets the values for the current skip data. |
| /// </summary> |
| public virtual void SetSkipData(int doc, bool storePayloads, int payloadLength) |
| { |
| this.curDoc = doc; |
| this.curStorePayloads = storePayloads; |
| this.curPayloadLength = payloadLength; |
| this.curFreqPointer = freqOutput.GetFilePointer(); |
| if (proxOutput != null) |
| { |
| this.curProxPointer = proxOutput.GetFilePointer(); |
| } |
| } |
| |
| public override void ResetSkip() |
| { |
| base.ResetSkip(); |
| Arrays.Fill(lastSkipDoc, 0); |
| Arrays.Fill(lastSkipPayloadLength, -1); // we don't have to write the first length in the skip list |
| Arrays.Fill(lastSkipFreqPointer, freqOutput.GetFilePointer()); |
| if (proxOutput != null) |
| { |
| Arrays.Fill(lastSkipProxPointer, proxOutput.GetFilePointer()); |
| } |
| } |
| |
| protected override void WriteSkipData(int level, IndexOutput skipBuffer) |
| { |
| // To efficiently store payloads in the posting lists we do not store the length of |
| // every payload. Instead we omit the length for a payload if the previous payload had |
| // the same length. |
| // However, in order to support skipping the payload length at every skip point must be known. |
| // So we use the same length encoding that we use for the posting lists for the skip data as well: |
| // Case 1: current field does not store payloads |
| // SkipDatum --> DocSkip, FreqSkip, ProxSkip |
| // DocSkip,FreqSkip,ProxSkip --> VInt |
| // DocSkip records the document number before every SkipInterval th document in TermFreqs. |
| // Document numbers are represented as differences from the previous value in the sequence. |
| // Case 2: current field stores payloads |
| // SkipDatum --> DocSkip, PayloadLength?, FreqSkip,ProxSkip |
| // DocSkip,FreqSkip,ProxSkip --> VInt |
| // PayloadLength --> VInt |
| // In this case DocSkip/2 is the difference between |
| // the current and the previous value. If DocSkip |
| // is odd, then a PayloadLength encoded as VInt follows, |
| // if DocSkip is even, then it is assumed that the |
| // current payload length equals the length at the previous |
| // skip point |
| if (curStorePayloads) |
| { |
| int delta = curDoc - lastSkipDoc[level]; |
| if (curPayloadLength == lastSkipPayloadLength[level]) |
| { |
| // the current payload length equals the length at the previous skip point, |
| // so we don't store the length again |
| skipBuffer.WriteVInt32(delta * 2); |
| } |
| else |
| { |
| // the payload length is different from the previous one. We shift the DocSkip, |
| // set the lowest bit and store the current payload length as VInt. |
| skipBuffer.WriteVInt32(delta * 2 + 1); |
| skipBuffer.WriteVInt32(curPayloadLength); |
| lastSkipPayloadLength[level] = curPayloadLength; |
| } |
| } |
| else |
| { |
| // current field does not store payloads |
| skipBuffer.WriteVInt32(curDoc - lastSkipDoc[level]); |
| } |
| |
| skipBuffer.WriteVInt32((int)(curFreqPointer - lastSkipFreqPointer[level])); |
| skipBuffer.WriteVInt32((int)(curProxPointer - lastSkipProxPointer[level])); |
| |
| lastSkipDoc[level] = curDoc; |
| |
| lastSkipFreqPointer[level] = curFreqPointer; |
| lastSkipProxPointer[level] = curProxPointer; |
| } |
| } |
| } |