HSQLDB example source code file (ScaledRAFileInJar.java)

This example HSQLDB source code file (ScaledRAFileInJar.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, datainputstream, datainputstream, filenotfoundexception, hsqlbytearrayinputstream, hsqlbytearrayinputstream, inputstream, io, ioexception, ioexception, scaledrafileinjar, scaledrafileinjar, scaledrainterface, string

The HSQLDB ScaledRAFileInJar.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.DataInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

import org.hsqldb.Database;
import org.hsqldb.lib.HsqlByteArrayInputStream;
import org.hsqldb.lib.ResourceStreamProvider;

/**
 * This class is a random access wrapper around a DataInputStream object and
 * enables access to cached tables when a database is included in a jar.
 *
 * A proof-of-concept prototype was first contributed by winfriedthom@users.
 *
 * @author Fred Toussi (fredt@users dot sourceforge.net)
 * @version  1.9.0
 * @since  1.8.0
 */
final class ScaledRAFileInJar implements ScaledRAInterface {

    DataInputStream          file;
    final String             fileName;
    long                     fileLength;
    boolean                  bufferDirty = true;
    byte[]                   buffer      = new byte[4096];
    HsqlByteArrayInputStream ba = new HsqlByteArrayInputStream(buffer);
    long                     bufferOffset;

    //
    long seekPosition;
    long realPosition;

    ScaledRAFileInJar(String name) throws FileNotFoundException, IOException {

        fileName = name;

        fileLength = getLength();

        resetStream();
    }

    public long length() throws IOException {
        return fileLength;
    }

    /**
     * Some JVM's do not allow seek beyond end of file, so zeros are written
     * first in that case. Reported by bohgammer@users in Open Disucssion
     * Forum.
     */
    public void seek(long position) throws IOException {
        seekPosition = position;
    }

    public long getFilePointer() throws IOException {
        return seekPosition;
    }

    private void readIntoBuffer() throws IOException {

        long filePos = seekPosition;

        bufferDirty = false;

        long subOffset  = filePos % buffer.length;
        long readLength = fileLength - (filePos - subOffset);

        if (readLength <= 0) {
            throw new IOException("read beyond end of file");
        }

        if (readLength > buffer.length) {
            readLength = buffer.length;
        }

        fileSeek(filePos - subOffset);
        file.readFully(buffer, 0, (int) readLength);

        bufferOffset = filePos - subOffset;
        realPosition = bufferOffset + readLength;
    }

    public int read() throws IOException {

        if (seekPosition >= fileLength) {
            return -1;
        }

        if (bufferDirty || seekPosition < bufferOffset
                || seekPosition >= bufferOffset + buffer.length) {
            readIntoBuffer();
        }

        ba.reset();
        ba.skip(seekPosition - bufferOffset);

        int val = ba.read();

        seekPosition++;

        return val;
    }

    public long readLong() throws IOException {

        long hi = readInt();
        long lo = readInt();

        return (hi << 32) + (lo & 0xffffffffL);
    }

    public int readInt() throws IOException {

        if (bufferDirty || seekPosition < bufferOffset
                || seekPosition >= bufferOffset + buffer.length) {
            readIntoBuffer();
        }

        ba.reset();
        ba.skip(seekPosition - bufferOffset);

        int val = ba.readInt();

        seekPosition += 4;

        return val;
    }

    public void read(byte[] b, int offset, int length) throws IOException {

        if (bufferDirty || seekPosition < bufferOffset
                || seekPosition >= bufferOffset + buffer.length) {
            readIntoBuffer();
        }

        ba.reset();
        ba.skip(seekPosition - bufferOffset);

        int bytesRead = ba.read(b, offset, length);

        seekPosition += bytesRead;

        if (bytesRead < length) {
            if (seekPosition != realPosition) {
                fileSeek(seekPosition);
            }

            file.readFully(b, offset + bytesRead, length - bytesRead);

            seekPosition += (length - bytesRead);
            realPosition = seekPosition;
        }
    }

    public void write(byte[] b, int off, int len) throws IOException {}

    public void writeInt(int i) throws IOException {}

    public void writeLong(long i) throws IOException {}

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

    public boolean isReadOnly() {
        return true;
    }

    public boolean wasNio() {
        return false;
    }

    private long getLength() throws IOException {

        int count = 0;
        resetStream();


        while(true) {
            if (file.read() < 1) {
                break;
            }

            count++;

        }

        return count;
    }
    private void resetStream() throws IOException {

        if (file != null) {
            file.close();
        }

        InputStream fis = ResourceStreamProvider.getResourceAsStream(fileName);

        file = new DataInputStream(fis);
    }

    private void fileSeek(long position) throws IOException {

        long skipPosition = realPosition;

        if (position < skipPosition) {
            resetStream();

            skipPosition = 0;
        }

        while (position > skipPosition) {
            skipPosition += file.skip(position - skipPosition);
        }
    }

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

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

    public Database getDatabase() {
        return null;
    }

    public void synch() {}
}