Lucene example source code file (RAMOutputStream.java)

This example Lucene source code file (RAMOutputStream.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, indexoutput, io, ioexception, ioexception, override, override, ramfile, ramoutputstream, ramoutputstream

The Lucene RAMOutputStream.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;

/**
 * A memory-resident {@link IndexOutput} implementation.
 *
 * @lucene.internal
 */
public class RAMOutputStream extends IndexOutput {
  static final int BUFFER_SIZE = 1024;

  private RAMFile file;

  private byte[] currentBuffer;
  private int currentBufferIndex;
  
  private int bufferPosition;
  private long bufferStart;
  private int bufferLength;

  /** Construct an empty output buffer. */
  public RAMOutputStream() {
    this(new RAMFile());
  }

  public RAMOutputStream(RAMFile f) {
    file = f;

    // make sure that we switch to the
    // first needed buffer lazily
    currentBufferIndex = -1;
    currentBuffer = null;
  }

  /** Copy the current contents of this buffer to the named output. */
  public void writeTo(IndexOutput out) throws IOException {
    flush();
    final long end = file.length;
    long pos = 0;
    int buffer = 0;
    while (pos < end) {
      int length = BUFFER_SIZE;
      long nextPos = pos + length;
      if (nextPos > end) {                        // at the last buffer
        length = (int)(end - pos);
      }
      out.writeBytes(file.getBuffer(buffer++), length);
      pos = nextPos;
    }
  }

  /** Resets this to an empty file. */
  public void reset() {
    currentBuffer = null;
    currentBufferIndex = -1;
    bufferPosition = 0;
    bufferStart = 0;
    bufferLength = 0;
    file.setLength(0);
  }

  @Override
  public void close() throws IOException {
    flush();
  }

  @Override
  public void seek(long pos) throws IOException {
    // set the file length in case we seek back
    // and flush() has not been called yet
    setFileLength();
    if (pos < bufferStart || pos >= bufferStart + bufferLength) {
      currentBufferIndex = (int) (pos / BUFFER_SIZE);
      switchCurrentBuffer();
    }

    bufferPosition = (int) (pos % BUFFER_SIZE);
  }

  @Override
  public long length() {
    return file.length;
  }

  @Override
  public void writeByte(byte b) throws IOException {
    if (bufferPosition == bufferLength) {
      currentBufferIndex++;
      switchCurrentBuffer();
    }
    currentBuffer[bufferPosition++] = b;
  }

  @Override
  public void writeBytes(byte[] b, int offset, int len) throws IOException {
    assert b != null;
    while (len > 0) {
      if (bufferPosition ==  bufferLength) {
        currentBufferIndex++;
        switchCurrentBuffer();
      }

      int remainInBuffer = currentBuffer.length - bufferPosition;
      int bytesToCopy = len < remainInBuffer ? len : remainInBuffer;
      System.arraycopy(b, offset, currentBuffer, bufferPosition, bytesToCopy);
      offset += bytesToCopy;
      len -= bytesToCopy;
      bufferPosition += bytesToCopy;
    }
  }

  private final void switchCurrentBuffer() throws IOException {
    if (currentBufferIndex == file.numBuffers()) {
      currentBuffer = file.addBuffer(BUFFER_SIZE);
    } else {
      currentBuffer = file.getBuffer(currentBufferIndex);
    }
    bufferPosition = 0;
    bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex;
    bufferLength = currentBuffer.length;
  }

  private void setFileLength() {
    long pointer = bufferStart + bufferPosition;
    if (pointer > file.length) {
      file.setLength(pointer);
    }
  }

  @Override
  public void flush() throws IOException {
    file.setLastModified(System.currentTimeMillis());
    setFileLength();
  }

  @Override
  public long getFilePointer() {
    return currentBufferIndex < 0 ? 0 : bufferStart + bufferPosition;
  }

  /** Returns byte usage of all buffers. */
  public long sizeInBytes() {
    return file.numBuffers() * BUFFER_SIZE;
  }
  
  @Override
  public void copyBytes(DataInput input, long numBytes) throws IOException {
    assert numBytes >= 0: "numBytes=" + numBytes;

    while (numBytes > 0) {
      if (bufferPosition == bufferLength) {
        currentBufferIndex++;
        switchCurrentBuffer();
      }

      int toCopy = currentBuffer.length - bufferPosition;
      if (numBytes < toCopy) {
        toCopy = (int) numBytes;
      }
      input.readBytes(currentBuffer, bufferPosition, toCopy, false);
      numBytes -= toCopy;
      bufferPosition += toCopy;
    }

  }
  
}