Lucene example source code file (CompoundFileReader.java)

This example Lucene source code file (CompoundFileReader.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

compoundfilereader, csindexinput, directory, eof, fileentry, indexinput, indexinput, io, ioexception, ioexception, override, override, string, string, unsupportedoperationexception, util

The Lucene CompoundFileReader.java source code

package org.apache.lucene.index;

/**
 * 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.
 */

import org.apache.lucene.store.Directory;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.BufferedIndexInput;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.store.Lock;

import java.util.HashMap;
import java.io.FileNotFoundException;
import java.io.IOException;

/**
 * Class for accessing a compound stream.
 * This class implements a directory, but is limited to only read operations.
 * Directory methods that would normally modify data throw an exception.
 */
class CompoundFileReader extends Directory {
  
  private int readBufferSize;
  
  private static final class FileEntry {
    long offset;
    long length;
  }
    
  // Base info
  private Directory directory;
  private String fileName;
  
  private IndexInput stream;
  private HashMap<String,FileEntry> entries = new HashMap();
  
  public CompoundFileReader(Directory dir, String name) throws IOException {
    this(dir, name, BufferedIndexInput.BUFFER_SIZE);
  }
  
  public CompoundFileReader(Directory dir, String name, int readBufferSize) throws IOException {
    assert !(dir instanceof CompoundFileReader) : "compound file inside of compound file: " + name;
    directory = dir;
    fileName = name;
    this.readBufferSize = readBufferSize;
    
    boolean success = false;
    
    try {
      stream = dir.openInput(name, readBufferSize);
      
      // read the first VInt. If it is negative, it's the version number
      // otherwise it's the count (pre-3.1 indexes)
      int firstInt = stream.readVInt();
      
      final int count;
      final boolean stripSegmentName;
      if (firstInt < CompoundFileWriter.FORMAT_PRE_VERSION) {
        if (firstInt < CompoundFileWriter.FORMAT_CURRENT) {
          throw new CorruptIndexException("Incompatible format version: "
              + firstInt + " expected " + CompoundFileWriter.FORMAT_CURRENT);
        }
        // It's a post-3.1 index, read the count.
        count = stream.readVInt();
        stripSegmentName = false;
      } else {
        count = firstInt;
        stripSegmentName = true;
      }
      
      // read the directory and init files
      FileEntry entry = null;
      for (int i=0; i<count; i++) {
        long offset = stream.readLong();
        String id = stream.readString();
        
        if (stripSegmentName) {
          // Fix the id to not include the segment names. This is relevant for
          // pre-3.1 indexes.
          id = IndexFileNames.stripSegmentName(id);
        }
        
        if (entry != null) {
          // set length of the previous entry
          entry.length = offset - entry.offset;
        }
        
        entry = new FileEntry();
        entry.offset = offset;
        entries.put(id, entry);
      }
      
      // set the length of the final entry
      if (entry != null) {
        entry.length = stream.length() - entry.offset;
      }
      
      success = true;
      
    } finally {
      if (!success && (stream != null)) {
        try {
          stream.close();
        } catch (IOException e) { }
      }
    }
  }
  
  public Directory getDirectory() {
    return directory;
  }
  
  public String getName() {
    return fileName;
  }
  
  @Override
  public synchronized void close() throws IOException {
    if (stream == null)
      throw new IOException("Already closed");
    
    entries.clear();
    stream.close();
    stream = null;
  }
  
  @Override
  public synchronized IndexInput openInput(String id) throws IOException {
    // Default to readBufferSize passed in when we were opened
    return openInput(id, readBufferSize);
  }
  
  @Override
  public synchronized IndexInput openInput(String id, int readBufferSize) throws IOException {
    if (stream == null)
      throw new IOException("Stream closed");
    
    id = IndexFileNames.stripSegmentName(id);
    FileEntry entry = entries.get(id);
    if (entry == null)
      throw new IOException("No sub-file with id " + id + " found (files: " + entries.keySet() + ")");
    
    return new CSIndexInput(stream, entry.offset, entry.length, readBufferSize);
  }
  
  /** Returns an array of strings, one for each file in the directory. */
  @Override
  public String[] listAll() {
    String[] res = entries.keySet().toArray(new String[entries.size()]);
    // Add the segment name
    String seg = fileName.substring(0, fileName.indexOf('.'));
    for (int i = 0; i < res.length; i++) {
      res[i] = seg + res[i];
    }
    return res;
  }
  
  /** Returns true iff a file with the given name exists. */
  @Override
  public boolean fileExists(String name) {
    return entries.containsKey(IndexFileNames.stripSegmentName(name));
  }
  
  /** Returns the time the compound file was last modified. */
  @Override
  public long fileModified(String name) throws IOException {
    return directory.fileModified(fileName);
  }
  
  /** Set the modified time of the compound file to now.
   *  @deprecated Lucene never uses this API; it will be
   *  removed in 4.0. */
  @Override
  @Deprecated
  public void touchFile(String name) throws IOException {
    directory.touchFile(fileName);
  }
  
  /** Not implemented
   * @throws UnsupportedOperationException */
  @Override
  public void deleteFile(String name) {
    throw new UnsupportedOperationException();
  }
  
  /** Not implemented
   * @throws UnsupportedOperationException */
  public void renameFile(String from, String to) {
    throw new UnsupportedOperationException();
  }
  
  /** Returns the length of a file in the directory.
   * @throws IOException if the file does not exist */
  @Override
  public long fileLength(String name) throws IOException {
    FileEntry e = entries.get(IndexFileNames.stripSegmentName(name));
    if (e == null)
      throw new FileNotFoundException(name);
    return e.length;
  }
  
  /** Not implemented
   * @throws UnsupportedOperationException */
  @Override
  public IndexOutput createOutput(String name) {
    throw new UnsupportedOperationException();
  }
  
  /** Not implemented
   * @throws UnsupportedOperationException */
  @Override
  public Lock makeLock(String name) {
    throw new UnsupportedOperationException();
  }
  
  /** Implementation of an IndexInput that reads from a portion of the
   *  compound file. The visibility is left as "package" *only* because
   *  this helps with testing since JUnit test cases in a different class
   *  can then access package fields of this class.
   */
  static final class CSIndexInput extends BufferedIndexInput {
    IndexInput base;
    long fileOffset;
    long length;
    
    CSIndexInput(final IndexInput base, final long fileOffset, final long length) {
      this(base, fileOffset, length, BufferedIndexInput.BUFFER_SIZE);
    }
    
    CSIndexInput(final IndexInput base, final long fileOffset, final long length, int readBufferSize) {
      super(readBufferSize);
      this.base = (IndexInput)base.clone();
      this.fileOffset = fileOffset;
      this.length = length;
    }
    
    @Override
    public Object clone() {
      CSIndexInput clone = (CSIndexInput)super.clone();
      clone.base = (IndexInput)base.clone();
      clone.fileOffset = fileOffset;
      clone.length = length;
      return clone;
    }
    
    /** Expert: implements buffer refill.  Reads bytes from the current
     *  position in the input.
     * @param b the array to read bytes into
     * @param offset the offset in the array to start storing bytes
     * @param len the number of bytes to read
     */
    @Override
    protected void readInternal(byte[] b, int offset, int len) throws IOException {
      long start = getFilePointer();
      if(start + len > length)
        throw new IOException("read past EOF");
      base.seek(fileOffset + start);
      base.readBytes(b, offset, len, false);
    }
    
    /** Expert: implements seek.  Sets current position in this file, where
     *  the next {@link #readInternal(byte[],int,int)} will occur.
     * @see #readInternal(byte[],int,int)
     */
    @Override
    protected void seekInternal(long pos) {}
    
    /** Closes the stream to further operations. */
    @Override
    public void close() throws IOException {
      base.close();
    }
    
    @Override
    public long length() {
      return length;
    }
    
    @Override
    public void copyBytes(IndexOutput out, long numBytes) throws IOException {
      // Copy first whatever is in the buffer
      numBytes -= flushBuffer(out, numBytes);
      
      // If there are more bytes left to copy, delegate the copy task to the
      // base IndexInput, in case it can do an optimized copy.
      if (numBytes > 0) {
        long start = getFilePointer();
        if (start + numBytes > length) {
          throw new IOException("read past EOF");
        }
        base.seek(fileOffset + start);
        base.copyBytes(out, numBytes);
      }
    }
  }
}