HSQLDB example source code file (ScaledRAFileHybrid.java)

This example HSQLDB source code file (ScaledRAFileHybrid.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

database, database, io, ioexception, ioexception, scaledrafile, scaledrafilehybrid, scaledrafilehybrid, scaledrafilenio, scaledrainterface, string, string, throwable

The HSQLDB ScaledRAFileHybrid.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 java.io.IOException;

import org.hsqldb.Database;

/**
 * Mixe NIO / non-NIO version of ScaledRAFile.
 * This class is used only for storing a CACHED
 * TABLE .data file and cannot be used for TEXT TABLE source files.
 *
 * Due to various issues with java.nio classes, this class will use a mapped
 * channel of fixed size. After reaching this size, the file and channel are
 * closed and a new one opened, up to the maximum size.
 *
 * @author fredt@users
 * @version  1.8.0.5
 * @since 1.7.2
 */
public final class ScaledRAFileHybrid implements ScaledRAInterface {

    final Database    database;
    final String      fileName;
    final boolean     isReadOnly;
    final boolean     wasNio;
    long              maxLength;
    ScaledRAInterface store;

    public ScaledRAFileHybrid(Database database, String name,
                              boolean readOnly) throws IOException {

        this.database   = database;
        this.fileName   = name;
        this.isReadOnly = readOnly;

        newStore(0);

        this.wasNio = store.wasNio();
    }

    public long length() throws IOException {
        return store.length();
    }

    public void seek(long position) throws IOException {
        checkSeek(position);
        store.seek(position);
    }

    public long getFilePointer() throws IOException {
        return store.getFilePointer();
    }

    public int read() throws IOException {

        checkLength(1);

        return store.read();
    }

    public void read(byte[] b, int offset, int length) throws IOException {
        checkLength(length);
        store.read(b, offset, length);
    }

    public void write(byte[] b, int offset, int length) throws IOException {
        checkLength(length);
        store.write(b, offset, length);
    }

    public int readInt() throws IOException {

        checkLength(4);

        return store.readInt();
    }

    public void writeInt(int i) throws IOException {
        checkLength(4);
        store.writeInt(i);
    }

    public long readLong() throws IOException {

        checkLength(8);

        return store.readLong();
    }

    public void writeLong(long i) throws IOException {
        checkLength(8);
        store.writeLong(i);
    }

    public void close() throws IOException {
        store.close();
    }

    public boolean isReadOnly() {
        return store.isReadOnly();
    }

    public boolean wasNio() {
        return wasNio;
    }

    public boolean canAccess(int length) {
        return true;
    }

    public boolean canSeek(long position) {
        return true;
    }

    public Database getDatabase() {
        return null;
    }

    public void synch() {
        store.synch();
    }

    private void checkLength(int length) throws IOException {

        if (store.canAccess(length)) {
            return;
        }

        newStore(store.getFilePointer() + length);
    }

    private void checkSeek(long position) throws IOException {

        if (store.canSeek(position)) {
            return;
        }

        newStore(position);
    }

    void newStore(long requiredPosition) throws IOException {

        long currentPosition = 0;

        if (store != null) {
            currentPosition = store.getFilePointer();

            store.close();
        }

        if (requiredPosition <= ScaledRAFile.MAX_NIO_LENGTH) {
            try {
                store = new ScaledRAFileNIO(database, fileName, isReadOnly,
                                            (int) requiredPosition);

                store.seek(currentPosition);

                return;
            } catch (Throwable e) {}
        }

        store = new ScaledRAFile(database, fileName, isReadOnly);

        store.seek(currentPosition);
    }
}