Quadcap Embeddable Database

com/quadcap/sql/file/RandomAccess.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.IOException;

/**
 * This interface is used to access a region of consecutive bytes in a
 * random access manner.<p>
 *
 * @author Stan Bailes
 */

public abstract class RandomAccess {
    byte[]              fmtBuf = new  byte[8];
    /**
     * Return the size of the managed region.
     */
    public abstract long size();

    /**
     * Resize the managed region.
     */
    public abstract void resize(long newSize) throws IOException;

    /* Write <tt>len</tt> bytes from position <tt>offset</tt> in buffer
     * <tt>buf</tt> to position <tt>pos</tt> bytes into the managed
     * area.
     */
    public abstract void write(long pos, byte[] buf, int offset, int len)
        throws IOException;

    /**
     * Read <tt>len</tt> bytes from location <tt>pos</tt> of the region
     * into the buffer <tt>buf</tt>, starting at <tt>offset</tt>.
     */
    public abstract void read(long pos, byte[] buf, int offset, int len)
        throws IOException;

    /**
     * Finalization...
     */
    public abstract void close() throws IOException;

    public abstract void flush() throws IOException;

    public void writeByte(int pos, int val) throws IOException {
        synchronized (fmtBuf) {
            fmtBuf[0] = (byte)(val & 0xff);
            write(pos, fmtBuf, 0, 1);
        }
    }

    public int readByte(int pos) throws IOException {
        synchronized (fmtBuf) {
            read(pos, fmtBuf, 0, 1);
            return fmtBuf[0] & 0xff;
        }
    }

    /**
     * Write a integer value to the specified position in the buffer
     */
    public void writeInt(long pos, int val) throws IOException {
        synchronized (fmtBuf) {
            ByteUtil.putInt(fmtBuf, 0, val);
            write(pos, fmtBuf, 0, 4);
        }
    }

    /**
     * Write a integer value to the specified position in the buffer
     */
    public int readInt(long pos) throws IOException {
        synchronized (fmtBuf) {        
            read(pos, fmtBuf, 0, 4);
            return ByteUtil.getInt(fmtBuf, 0);
        }
    }

    /**
     * Write a long value to the specified position in the buffer
     */
    public void writeLong(long pos, long val) throws IOException {
        synchronized (fmtBuf) {
            ByteUtil.putLong(fmtBuf, 0, val);
            write(pos, fmtBuf, 0, 8);
        }
    }

    /**
     * Write a long value to the specified position in the buffer
     */
    public long readLong(long pos) throws IOException {
        synchronized (fmtBuf) {
            read(pos, fmtBuf, 0, 8);
            return ByteUtil.getLong(fmtBuf, 0);
        }
    }
}