src/org/hsqldb/persist/LobStoreMem.java

/* Copyright (c) 2001-2010, The HSQL Development Group
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 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
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 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
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 * 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
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package org.hsqldb.persist;

import org.hsqldb.lib.HsqlArrayList;

/**
 * @author Fred Toussi (fredt@users dot sourceforge.net)
 * @version 1.9.0
 * @since 1.9.0
 */
public class LobStoreMem implements LobStore {

    final int     lobBlockSize;
    int           blocksInLargeBlock = 128;
    int           largeBlockSize;
    HsqlArrayList byteStoreList;

    public LobStoreMem(int lobBlockSize) {

        this.lobBlockSize = lobBlockSize;
        largeBlockSize    = lobBlockSize * blocksInLargeBlock;
        byteStoreList     = new HsqlArrayList();
    }

    public byte[] getBlockBytes(int blockAddress, int blockCount) {

        byte[] dataBytes       = new byte[blockCount * lobBlockSize];
        int    dataBlockOffset = 0;

        while (blockCount > 0) {
            int    largeBlockIndex   = blockAddress / blocksInLargeBlock;
            byte[] largeBlock = (byte[]) byteStoreList.get(largeBlockIndex);
            int    blockOffset       = blockAddress % blocksInLargeBlock;
            int    currentBlockCount = blockCount;

            if ((blockOffset + currentBlockCount) > blocksInLargeBlock) {
                currentBlockCount = blocksInLargeBlock - blockOffset;
            }

            System.arraycopy(largeBlock, blockOffset * lobBlockSize,
                             dataBytes, dataBlockOffset * lobBlockSize,
                             currentBlockCount * lobBlockSize);

            blockAddress    += currentBlockCount;
            dataBlockOffset += currentBlockCount;
            blockCount      -= currentBlockCount;
        }

        return dataBytes;
    }

    public void setBlockBytes(byte[] dataBytes, int blockAddress,
                              int blockCount) {

        int dataBlockOffset = 0;

        while (blockCount > 0) {
            int largeBlockIndex = blockAddress / blocksInLargeBlock;
            int largeBlockLimit = (blockAddress + blockCount)
                                  / blocksInLargeBlock;

            if ((blockAddress + blockCount) % blocksInLargeBlock != 0) {
                largeBlockLimit++;
            }

            if (largeBlockIndex >= byteStoreList.size()) {
                byteStoreList.add(new byte[largeBlockSize]);
            }

            byte[] largeBlock = (byte[]) byteStoreList.get(largeBlockIndex);
            int    blockOffset       = blockAddress % blocksInLargeBlock;
            int    currentBlockCount = blockCount;

            if ((blockOffset + currentBlockCount) > blocksInLargeBlock) {
                currentBlockCount = blocksInLargeBlock - blockOffset;
            }

            System.arraycopy(dataBytes, dataBlockOffset * lobBlockSize,
                             largeBlock, blockOffset * lobBlockSize,
                             currentBlockCount * lobBlockSize);

            blockAddress    += currentBlockCount;
            dataBlockOffset += currentBlockCount;
            blockCount      -= currentBlockCount;
        }
    }

    public int getBlockSize() {
        return lobBlockSize;
    }

    public void close() {
        byteStoreList.clear();
    }
}