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Lucene example source code file (BufferedIndexOutput.java)

This example Lucene source code file (BufferedIndexOutput.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

buffer_size, buffer_size, bufferedindexoutput, bufferedindexoutput, indexoutput, io, ioexception, ioexception, override, override

The Lucene BufferedIndexOutput.java source code

package org.apache.lucene.store;

/**
 * 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 java.io.IOException;

/** Base implementation class for buffered {@link IndexOutput}. */
public abstract class BufferedIndexOutput extends IndexOutput {
  static final int BUFFER_SIZE = 16384;

  private final byte[] buffer = new byte[BUFFER_SIZE];
  private long bufferStart = 0;           // position in file of buffer
  private int bufferPosition = 0;         // position in buffer

  /** Writes a single byte.
   * @see IndexInput#readByte()
   */
  @Override
  public void writeByte(byte b) throws IOException {
    if (bufferPosition >= BUFFER_SIZE)
      flush();
    buffer[bufferPosition++] = b;
  }

  /** Writes an array of bytes.
   * @param b the bytes to write
   * @param length the number of bytes to write
   * @see IndexInput#readBytes(byte[],int,int)
   */
  @Override
  public void writeBytes(byte[] b, int offset, int length) throws IOException {
    int bytesLeft = BUFFER_SIZE - bufferPosition;
    // is there enough space in the buffer?
    if (bytesLeft >= length) {
      // we add the data to the end of the buffer
      System.arraycopy(b, offset, buffer, bufferPosition, length);
      bufferPosition += length;
      // if the buffer is full, flush it
      if (BUFFER_SIZE - bufferPosition == 0)
        flush();
    } else {
      // is data larger then buffer?
      if (length > BUFFER_SIZE) {
        // we flush the buffer
        if (bufferPosition > 0)
          flush();
        // and write data at once
        flushBuffer(b, offset, length);
        bufferStart += length;
      } else {
        // we fill/flush the buffer (until the input is written)
        int pos = 0; // position in the input data
        int pieceLength;
        while (pos < length) {
          pieceLength = (length - pos < bytesLeft) ? length - pos : bytesLeft;
          System.arraycopy(b, pos + offset, buffer, bufferPosition, pieceLength);
          pos += pieceLength;
          bufferPosition += pieceLength;
          // if the buffer is full, flush it
          bytesLeft = BUFFER_SIZE - bufferPosition;
          if (bytesLeft == 0) {
            flush();
            bytesLeft = BUFFER_SIZE;
          }
        }
      }
    }
  }

  /** Forces any buffered output to be written. */
  @Override
  public void flush() throws IOException {
    flushBuffer(buffer, bufferPosition);
    bufferStart += bufferPosition;
    bufferPosition = 0;
  }

  /** Expert: implements buffer write.  Writes bytes at the current position in
   * the output.
   * @param b the bytes to write
   * @param len the number of bytes to write
   */
  private void flushBuffer(byte[] b, int len) throws IOException {
    flushBuffer(b, 0, len);
  }

  /** Expert: implements buffer write.  Writes bytes at the current position in
   * the output.
   * @param b the bytes to write
   * @param offset the offset in the byte array
   * @param len the number of bytes to write
   */
  protected abstract void flushBuffer(byte[] b, int offset, int len) throws IOException;
  
  /** Closes this stream to further operations. */
  @Override
  public void close() throws IOException {
    flush();
  }

  /** Returns the current position in this file, where the next write will
   * occur.
   * @see #seek(long)
   */
  @Override
  public long getFilePointer() {
    return bufferStart + bufferPosition;
  }

  /** Sets current position in this file, where the next write will occur.
   * @see #getFilePointer()
   */
  @Override
  public void seek(long pos) throws IOException {
    flush();
    bufferStart = pos;
  }

  /** The number of bytes in the file. */
  @Override
  public abstract long length() throws IOException;


}

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Here is a short list of links related to this Lucene BufferedIndexOutput.java source code file:



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