OSysBucket.java example

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orientdb-master
/*
 *
 *  *  Copyright 2014 Orient Technologies LTD (info(at)orientechnologies.com)
 *  *
 *  *  Licensed 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.
 *  *
 *  * For more information: http://www.orientechnologies.com
 *
 */

package com.orientechnologies.orient.core.index.sbtreebonsai.local;

import com.orientechnologies.common.serialization.types.OByteSerializer;
import com.orientechnologies.common.serialization.types.OLongSerializer;
import com.orientechnologies.orient.core.storage.cache.OCacheEntry;
import com.orientechnologies.orient.core.storage.impl.local.paginated.wal.OWALChanges;

import java.io.IOException;

/**
 * <p>
 * A system bucket for bonsai tree pages. Single per file.
 * </p>
 * <p>
 * Holds an information about:
 * </p>
 * <ul>
 * <li>head of free list</li>
 * <li>length of free list</li>
 * <li>pointer to free space</li>
 * </ul>
 * 
 * @author Artem Orobets (enisher-at-gmail.com)
 */
public class OSysBucket extends OBonsaiBucketAbstract {
  private static final int  SYS_MAGIC_OFFSET        = WAL_POSITION_OFFSET + OLongSerializer.LONG_SIZE;
  private static final int  FREE_SPACE_OFFSET       = SYS_MAGIC_OFFSET + OByteSerializer.BYTE_SIZE;
  private static final int  FREE_LIST_HEAD_OFFSET   = FREE_SPACE_OFFSET + OBonsaiBucketPointer.SIZE;
  private static final int  FREE_LIST_LENGTH_OFFSET = FREE_LIST_HEAD_OFFSET + OBonsaiBucketPointer.SIZE;

  /**
   * Magic number to check if the sys bucket is initialized.
   */
  private static final byte SYS_MAGIC               = (byte) 41;

  public OSysBucket(OCacheEntry cacheEntry, OWALChanges changes) {
    super(cacheEntry, changes);
  }

  public void init() throws IOException {
    setByteValue(SYS_MAGIC_OFFSET, SYS_MAGIC);
    setBucketPointer(FREE_SPACE_OFFSET, new OBonsaiBucketPointer(0, OSBTreeBonsaiBucket.MAX_BUCKET_SIZE_BYTES));
    setBucketPointer(FREE_LIST_HEAD_OFFSET, OBonsaiBucketPointer.NULL);
    setLongValue(FREE_LIST_LENGTH_OFFSET, 0L);
  }

  public boolean isInitialized() {
    return getByteValue(SYS_MAGIC_OFFSET) != 41;
  }

  public long freeListLength() {
    return getLongValue(FREE_LIST_LENGTH_OFFSET);
  }

  public void setFreeListLength(long length) throws IOException {
    setLongValue(FREE_LIST_LENGTH_OFFSET, length);
  }

  public OBonsaiBucketPointer getFreeSpacePointer() {
    return getBucketPointer(FREE_SPACE_OFFSET);
  }

  public void setFreeSpacePointer(OBonsaiBucketPointer pointer) throws IOException {
    setBucketPointer(FREE_SPACE_OFFSET, pointer);
  }

  public OBonsaiBucketPointer getFreeListHead() {
    return getBucketPointer(FREE_LIST_HEAD_OFFSET);
  }

  public void setFreeListHead(OBonsaiBucketPointer pointer) throws IOException {
    setBucketPointer(FREE_LIST_HEAD_OFFSET, pointer);
  }
}