HSQLDB example source code file (DataFileBlockManager.java)

This example HSQLDB source code file (DataFileBlockManager.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 - HSQLDB tags/keywords

datafileblockmanager, datafileblockmanager, doubleintindex, doubleintindex, nullpointerexception, nullpointerexception

The HSQLDB DataFileBlockManager.java source code

/* Copyright (c) 2001-2008, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


package org.hsqldb.persist;

import org.hsqldb.lib.DoubleIntIndex;

/**
 * Maintains a list of free file blocks with fixed capacity.<p>
 *
 * @author fredt@users
 * @version 1.8.0
 * @since 1.8.0
 */
public class DataFileBlockManager {

    private DoubleIntIndex lookup;
    private final int      capacity;
    private int            midSize;
    private final int      scale;
    private long           releaseCount;
    private long           requestCount;
    private long           requestSize;

    // reporting vars
    long    lostFreeBlockSize;
    boolean isModified;

    /**
     *
     */
    public DataFileBlockManager(int capacity, int scale, long lostSize) {

        lookup = new DoubleIntIndex(capacity, true);

        lookup.setValuesSearchTarget();

        this.capacity          = capacity;
        this.scale             = scale;
        this.lostFreeBlockSize = lostSize;
        this.midSize           = 128;    // arbitrary initial value
    }

    /**
     */
    void add(int pos, int rowSize) {

        isModified = true;

        if (capacity == 0) {
            lostFreeBlockSize += rowSize;

            return;
        }

        releaseCount++;

        //
        if (lookup.size() == capacity) {
            resetList();
        }

        lookup.add(pos, rowSize);
    }

    /**
     * Returns the position of a free block or 0.
     */
    int get(int rowSize) {

        if (lookup.size() == 0) {
            return -1;
        }

        int index = lookup.findFirstGreaterEqualKeyIndex(rowSize);

        if (index == -1) {
            return -1;
        }

        // statistics for successful requests only - to be used later for midSize
        requestCount++;

        requestSize += rowSize;

        int length     = lookup.getValue(index);
        int difference = length - rowSize;
        int key        = lookup.getKey(index);

        lookup.remove(index);

        if (difference >= midSize) {
            int pos = key + (rowSize / scale);

            lookup.add(pos, difference);
        } else {
            lostFreeBlockSize += difference;
        }

        return key;
    }

    int size() {
        return lookup.size();
    }

    long getLostBlocksSize() {
        return lostFreeBlockSize;
    }

    boolean isModified() {
        return isModified;
    }

    void clear() {
        removeBlocks(lookup.size());
    }

    private void resetList() {

        if (requestCount != 0) {
            midSize = (int) (requestSize / requestCount);
        }

        int first = lookup.findFirstGreaterEqualSlotIndex(midSize);

        if (first < lookup.size() / 4) {
            first = lookup.size() / 4;
        }

        removeBlocks(first);
    }

    private void removeBlocks(int blocks) {

        for (int i = 0; i < blocks; i++) {
            lostFreeBlockSize += lookup.getValue(i);
        }

        lookup.removeRange(0, blocks);
    }

    private void checkIntegrity() throws NullPointerException {}
}