org.apache.lucene.codecs.lucene50.Lucene50CompoundFormat Maven / Gradle / Ivy

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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.
 */
package org.apache.lucene.codecs.lucene50;


import java.io.IOException;
import java.util.Collection;

import org.apache.lucene.codecs.CodecUtil;
import org.apache.lucene.codecs.CompoundFormat;
import org.apache.lucene.index.IndexFileNames;
import org.apache.lucene.index.SegmentInfo;
import org.apache.lucene.store.DataOutput;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.IOContext;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.IndexOutput;

/**
 * Lucene 5.0 compound file format
 * 
 * Files:
 * 

 *    .cfs: An optional "virtual" file consisting of all the other 
 *    index files for systems that frequently run out of file handles.
 *    
.cfe: The "virtual" compound file's entry table holding all 
 *    entries in the corresponding .cfs file.
 * 
 * Description:
 * 
 *   Compound (.cfs) --> Header, FileData ^FileCount, Footer
 *   Compound Entry Table (.cfe) --> Header, FileCount, <FileName,
 *       DataOffset, DataLength> ^FileCount
 *   Header --> {@link CodecUtil#writeIndexHeader IndexHeader}
 *   FileCount --> {@link DataOutput#writeVInt VInt}
 *   DataOffset,DataLength,Checksum --> {@link DataOutput#writeLong UInt64}
 *   FileName --> {@link DataOutput#writeString String}
 *   FileData --> raw file data
 *   Footer --> {@link CodecUtil#writeFooter CodecFooter}
 * 
 * Notes:
 * 
 *   FileCount indicates how many files are contained in this compound file. 
 *       The entry table that follows has that many entries. 
 *   
Each directory entry contains a long pointer to the start of this file's data
 *       section, the files length, and a String with that file's name.
 * 
 */
public final class Lucene50CompoundFormat extends CompoundFormat {

  /** Sole constructor. */
  public Lucene50CompoundFormat() {
  }
  
  @Override
  public Directory getCompoundReader(Directory dir, SegmentInfo si, IOContext context) throws IOException {
    return new Lucene50CompoundReader(dir, si, context);
  }

  @Override
  public void write(Directory dir, SegmentInfo si, IOContext context) throws IOException {
    String dataFile = IndexFileNames.segmentFileName(si.name, "", DATA_EXTENSION);
    String entriesFile = IndexFileNames.segmentFileName(si.name, "", ENTRIES_EXTENSION);
    
    try (IndexOutput data =    dir.createOutput(dataFile, context);
         IndexOutput entries = dir.createOutput(entriesFile, context)) {
      CodecUtil.writeIndexHeader(data,    DATA_CODEC, VERSION_CURRENT, si.getId(), "");
      CodecUtil.writeIndexHeader(entries, ENTRY_CODEC, VERSION_CURRENT, si.getId(), "");
      
      // write number of files
      entries.writeVInt(si.files().size());
      for (String file : si.files()) {
        
        // write bytes for file
        long startOffset = data.getFilePointer();
        try (IndexInput in = dir.openInput(file, IOContext.READONCE)) {
          data.copyBytes(in, in.length());
        }
        long endOffset = data.getFilePointer();
        
        long length = endOffset - startOffset;
        
        // write entry for file
        entries.writeString(IndexFileNames.stripSegmentName(file));
        entries.writeLong(startOffset);
        entries.writeLong(length);
      }
      
      CodecUtil.writeFooter(data);
      CodecUtil.writeFooter(entries);
    }
  }

  /** Extension of compound file */
  static final String DATA_EXTENSION = "cfs";
  /** Extension of compound file entries */
  static final String ENTRIES_EXTENSION = "cfe";
  static final String DATA_CODEC = "Lucene50CompoundData";
  static final String ENTRY_CODEC = "Lucene50CompoundEntries";
  static final int VERSION_START = 0;
  static final int VERSION_CURRENT = VERSION_START;
}