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Lucene example source code file (SegmentNorms.java)

This example Lucene source code file (SegmentNorms.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

atomicinteger, atomicinteger, clonenotsupportedexception, clonenotsupportedexception, indexoutput, io, ioexception, ioexception, n','r','m',-1, norms_header, object, segmentnorms, segmentnorms, segmentreader, string

The Lucene SegmentNorms.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 java.io.IOException;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.IndexOutput;

/**
 * Byte[] referencing is used because a new norm object needs 
 * to be created for each clone, and the byte array is all 
 * that is needed for sharing between cloned readers.  The 
 * current norm referencing is for sharing between readers 
 * whereas the byte[] referencing is for copy on write which 
 * is independent of reader references (i.e. incRef, decRef).
 */

final class SegmentNorms implements Cloneable {

  /** norms header placeholder */
  static final byte[] NORMS_HEADER = new byte[]{'N','R','M',-1};

  int refCount = 1;

  // If this instance is a clone, the originalNorm
  // references the Norm that has a real open IndexInput:
  private SegmentNorms origNorm;

  private IndexInput in;
  private long normSeek;

  // null until bytes is set
  private AtomicInteger bytesRef;
  private byte[] bytes;
  private int number;

  boolean dirty;
  boolean rollbackDirty;
  
  private final SegmentReader owner;
  
  public SegmentNorms(IndexInput in, int number, long normSeek, SegmentReader owner) {
    this.in = in;
    this.number = number;
    this.normSeek = normSeek;
    this.owner = owner;
  }

  public synchronized void incRef() {
    assert refCount > 0 && (origNorm == null || origNorm.refCount > 0);
    refCount++;
  }

  private void closeInput() throws IOException {
    if (in != null) {
      if (in != owner.singleNormStream) {
        // It's private to us -- just close it
        in.close();
      } else {
        // We are sharing this with others -- decRef and
        // maybe close the shared norm stream
        if (owner.singleNormRef.decrementAndGet() == 0) {
          owner.singleNormStream.close();
          owner.singleNormStream = null;
        }
      }

      in = null;
    }
  }

  public synchronized void decRef() throws IOException {
    assert refCount > 0 && (origNorm == null || origNorm.refCount > 0);

    if (--refCount == 0) {
      if (origNorm != null) {
        origNorm.decRef();
        origNorm = null;
      } else {
        closeInput();
      }

      if (bytes != null) {
        assert bytesRef != null;
        bytesRef.decrementAndGet();
        bytes = null;
        bytesRef = null;
      } else {
        assert bytesRef == null;
      }
    }
  }

  // Load bytes but do not cache them if they were not
  // already cached
  public synchronized void bytes(byte[] bytesOut, int offset, int len) throws IOException {
    assert refCount > 0 && (origNorm == null || origNorm.refCount > 0);
    if (bytes != null) {
      // Already cached -- copy from cache:
      assert len <= owner.maxDoc();
      System.arraycopy(bytes, 0, bytesOut, offset, len);
    } else {
      // Not cached
      if (origNorm != null) {
        // Ask origNorm to load
        origNorm.bytes(bytesOut, offset, len);
      } else {
        // We are orig -- read ourselves from disk:
        synchronized(in) {
          in.seek(normSeek);
          in.readBytes(bytesOut, offset, len, false);
        }
      }
    }
  }

  // Load & cache full bytes array.  Returns bytes.
  public synchronized byte[] bytes() throws IOException {
    assert refCount > 0 && (origNorm == null || origNorm.refCount > 0);
    if (bytes == null) {                     // value not yet read
      assert bytesRef == null;
      if (origNorm != null) {
        // Ask origNorm to load so that for a series of
        // reopened readers we share a single read-only
        // byte[]
        bytes = origNorm.bytes();
        bytesRef = origNorm.bytesRef;
        bytesRef.incrementAndGet();

        // Once we've loaded the bytes we no longer need
        // origNorm:
        origNorm.decRef();
        origNorm = null;

      } else {
        // We are the origNorm, so load the bytes for real
        // ourself:
        final int count = owner.maxDoc();
        bytes = new byte[count];

        // Since we are orig, in must not be null
        assert in != null;

        // Read from disk.
        synchronized(in) {
          in.seek(normSeek);
          in.readBytes(bytes, 0, count, false);
        }

        bytesRef = new AtomicInteger(1);
        closeInput();
      }
    }

    return bytes;
  }

  // Only for testing
  AtomicInteger bytesRef() {
    return bytesRef;
  }

  // Called if we intend to change a norm value.  We make a
  // private copy of bytes if it's shared with others:
  public synchronized byte[] copyOnWrite() throws IOException {
    assert refCount > 0 && (origNorm == null || origNorm.refCount > 0);
    bytes();
    assert bytes != null;
    assert bytesRef != null;
    if (bytesRef.get() > 1) {
      // I cannot be the origNorm for another norm
      // instance if I'm being changed.  Ie, only the
      // "head Norm" can be changed:
      assert refCount == 1;
      final AtomicInteger oldRef = bytesRef;
      bytes = owner.cloneNormBytes(bytes);
      bytesRef = new AtomicInteger(1);
      oldRef.decrementAndGet();
    }
    dirty = true;
    return bytes;
  }
  
  // Returns a copy of this Norm instance that shares
  // IndexInput & bytes with the original one
  @Override
  public synchronized Object clone() {
    assert refCount > 0 && (origNorm == null || origNorm.refCount > 0);
      
    SegmentNorms clone;
    try {
      clone = (SegmentNorms) super.clone();
    } catch (CloneNotSupportedException cnse) {
      // Cannot happen
      throw new RuntimeException("unexpected CloneNotSupportedException", cnse);
    }
    clone.refCount = 1;

    if (bytes != null) {
      assert bytesRef != null;
      assert origNorm == null;

      // Clone holds a reference to my bytes:
      clone.bytesRef.incrementAndGet();
    } else {
      assert bytesRef == null;
      if (origNorm == null) {
        // I become the origNorm for the clone:
        clone.origNorm = this;
      }
      clone.origNorm.incRef();
    }

    // Only the origNorm will actually readBytes from in:
    clone.in = null;

    return clone;
  }

  // Flush all pending changes to the next generation
  // separate norms file.
  public void reWrite(SegmentInfo si) throws IOException {
    assert refCount > 0 && (origNorm == null || origNorm.refCount > 0): "refCount=" + refCount + " origNorm=" + origNorm;

    // NOTE: norms are re-written in regular directory, not cfs
    si.advanceNormGen(this.number);
    final String normFileName = si.getNormFileName(this.number);
    IndexOutput out = owner.directory().createOutput(normFileName);
    boolean success = false;
    try {
      try {
        out.writeBytes(SegmentNorms.NORMS_HEADER, 0, SegmentNorms.NORMS_HEADER.length);
        out.writeBytes(bytes, owner.maxDoc());
      } finally {
        out.close();
      }
      success = true;
    } finally {
      if (!success) {
        try {
          owner.directory().deleteFile(normFileName);
        } catch (Throwable t) {
          // suppress this so we keep throwing the
          // original exception
        }
      }
    }
    this.dirty = false;
  }
}

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