Quadcap Embeddable Database

com/quadcap/sql/file/MemoryBlockStore.java

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package com.quadcap.sql.file;

/* Copyright 1997 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.io.File;
import java.io.FileDescriptor;
import java.io.IOException;
import java.io.RandomAccessFile;

import java.util.BitSet;

import com.quadcap.util.collections.LongIterator;
import com.quadcap.util.collections.LongMap;

import com.quadcap.util.Debug;
import com.quadcap.util.Util;

import com.quadcap.sql.Version;

/**
 * Below the cache, this class handles the actual I/O to the underlying file.
 * Block write operations are logged by this class.
 *
 * @author Stan Bailes
 */
public class MemoryBlockStore extends  BlockStore {
    LongMap                         blocks;

    public MemoryBlockStore() {}

    /**
     * Initialize a new BlockStore object using the specified file and
     * blocksize.
     *
     * @param file the underlying file.
     * @param mode "r" for readonly access, otherwise "rw"
     * @param blocksize the block size to use when creating the file.
     * @param the synchronization object
     */
    public void init(File file, String mode, int blockSize, Object lock)
        throws IOException
    {
        this.blockSize = blockSize;
        this.lock = lock;
        this.blocks = new LongMap(8888);
        createHeader(blockSize);
    }

    /**
     * Read a block into a buffer.  If the specified block is beyond the
     * current end of file, then grow the file
     *
     * @param blockNum the number of the block to read.
     * @param buf the buffer into which the data is read.
     */
    public void read(long blockNum, byte[] buf, int off)
        throws IOException
    {
        //bug.println("read(" + blockNum + ")");
        synchronized (lock) {
            byte[] block = (byte[])blocks.get(blockNum);
            if (block == null) {
                block = new byte[blockSize];
                blocks.put(blockNum, block);
            }
            System.arraycopy(block, 0, buf, off, blockSize);
            readCount++;
        }
    }
    
    /**
     * Write a block from a buffer into the file.
     *
     * @param blockNum the number of the block to write.
     * @param buf the buffer from which the data is written.
     * @exception IOException if an I/O error occurs.
     */
    public void write(long blockNum, byte[] buf)
        throws IOException
    {
        //bug.println("write(" + blockNum + "): \n" + Util.strBytes(buf, 0, 64));
        synchronized (lock) {
            byte[] block = (byte[])blocks.get(blockNum);
            boolean exists = (block != null);
            if (!exists) {
                block = new byte[blockSize];
                blocks.put(blockNum, block);
            }
            if (log != null && !modified.get((int)blockNum)) {
                modified.set((int)blockNum);
                if (exists) {
                    log.saveBlock(blockNum);
                }
            }
            System.arraycopy(buf, 0, block, 0, blockSize);
            writeCount++;
            //#ifdef DEBUG
            if (Trace.bit(20)) {
                Debug.println(toString() + ".write(" + blockNum + ")");
            }
            //#endif
        }
    }

    /**
     * Restore a block image
     */
    public void restore(long blockNum, byte[] buf, int off)
        throws IOException
    {
        synchronized (lock) {
            byte[] block = (byte[]) blocks.get(blockNum);
            if (block == null) {
                throw new IOException("No block to restore: " + blockNum);
            }
            System.arraycopy(buf, off, block, 0, blockSize);
        }
        
    }

    public void setLength(long length) throws IOException {
        length /= blockSize;
        LongIterator iter = blocks.keys();
        while (iter.hasNext()) {
            long blockNum = iter.nextLong();
            if (blockNum >= length) {
                iter.remove();
            }
        }
    }

    private void createHeader(int blockSize) throws IOException {
        this.blockSize = blockSize;
        byte[] buf = newHeader(blockSize, 2);
        blocks.put(0, buf);
    }

    public boolean isEncrypted() {
        return false;
    }
    
    public void close() throws IOException {
    }

    public void flush() throws IOException {
        readCount = writeCount = 0;
    }

    //#ifdef JDK14
    public void setKey(com.quadcap.crypto.SymmetricKey key)
        throws IOException
    {
        throw new IOException("Not encrypted");
    }
    //#endif
    
    //#ifdef DEBUG
    public String toString() {
        return "MemoryBlockStore()";
    }

    public static String rw() {
        return "(r=" + BlockStore.readCount +
            " w=" + BlockStore.writeCount + ")";
    }
                   
    //#endif

}