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Lucene example source code file (ByteSliceReader.java)

This example Lucene source code file (ByteSliceReader.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

byteblockpool, byteblockpool, byteslicereader, indexinput, indexinput, io, ioexception, override, override, runtimeexception, runtimeexception

The Lucene ByteSliceReader.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.IndexInput;
import org.apache.lucene.store.IndexOutput;
import java.io.IOException;

/* IndexInput that knows how to read the byte slices written
 * by Posting and PostingVector.  We read the bytes in
 * each slice until we hit the end of that slice at which
 * point we read the forwarding address of the next slice
 * and then jump to it.*/
final class ByteSliceReader extends IndexInput {
  ByteBlockPool pool;
  int bufferUpto;
  byte[] buffer;
  public int upto;
  int limit;
  int level;
  public int bufferOffset;

  public int endIndex;

  public void init(ByteBlockPool pool, int startIndex, int endIndex) {

    assert endIndex-startIndex >= 0;
    assert startIndex >= 0;
    assert endIndex >= 0;

    this.pool = pool;
    this.endIndex = endIndex;

    level = 0;
    bufferUpto = startIndex / DocumentsWriter.BYTE_BLOCK_SIZE;
    bufferOffset = bufferUpto * DocumentsWriter.BYTE_BLOCK_SIZE;
    buffer = pool.buffers[bufferUpto];
    upto = startIndex & DocumentsWriter.BYTE_BLOCK_MASK;

    final int firstSize = ByteBlockPool.levelSizeArray[0];

    if (startIndex+firstSize >= endIndex) {
      // There is only this one slice to read
      limit = endIndex & DocumentsWriter.BYTE_BLOCK_MASK;
    } else
      limit = upto+firstSize-4;
  }

  public boolean eof() {
    assert upto + bufferOffset <= endIndex;
    return upto + bufferOffset == endIndex;
  }

  @Override
  public byte readByte() {
    assert !eof();
    assert upto <= limit;
    if (upto == limit)
      nextSlice();
    return buffer[upto++];
  }

  public long writeTo(IndexOutput out) throws IOException {
    long size = 0;
    while(true) {
      if (limit + bufferOffset == endIndex) {
        assert endIndex - bufferOffset >= upto;
        out.writeBytes(buffer, upto, limit-upto);
        size += limit-upto;
        break;
      } else {
        out.writeBytes(buffer, upto, limit-upto);
        size += limit-upto;
        nextSlice();
      }
    }

    return size;
  }

  public void nextSlice() {

    // Skip to our next slice
    final int nextIndex = ((buffer[limit]&0xff)<<24) + ((buffer[1+limit]&0xff)<<16) + ((buffer[2+limit]&0xff)<<8) + (buffer[3+limit]&0xff);

    level = ByteBlockPool.nextLevelArray[level];
    final int newSize = ByteBlockPool.levelSizeArray[level];

    bufferUpto = nextIndex / DocumentsWriter.BYTE_BLOCK_SIZE;
    bufferOffset = bufferUpto * DocumentsWriter.BYTE_BLOCK_SIZE;

    buffer = pool.buffers[bufferUpto];
    upto = nextIndex & DocumentsWriter.BYTE_BLOCK_MASK;

    if (nextIndex + newSize >= endIndex) {
      // We are advancing to the final slice
      assert endIndex - nextIndex > 0;
      limit = endIndex - bufferOffset;
    } else {
      // This is not the final slice (subtract 4 for the
      // forwarding address at the end of this new slice)
      limit = upto+newSize-4;
    }
  }

  @Override
  public void readBytes(byte[] b, int offset, int len) {
    while(len > 0) {
      final int numLeft = limit-upto;
      if (numLeft < len) {
        // Read entire slice
        System.arraycopy(buffer, upto, b, offset, numLeft);
        offset += numLeft;
        len -= numLeft;
        nextSlice();
      } else {
        // This slice is the last one
        System.arraycopy(buffer, upto, b, offset, len);
        upto += len;
        break;
      }
    }
  }

  @Override
  public long getFilePointer() {throw new RuntimeException("not implemented");}
  @Override
  public long length() {throw new RuntimeException("not implemented");}
  @Override
  public void seek(long pos) {throw new RuntimeException("not implemented");}
  @Override
  public void close() {throw new RuntimeException("not implemented");}
}

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