Quadcap Embeddable Database

com/quadcap/sql/file/RandomAccessInputStream.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.InputStream;
import java.io.IOException;

import com.quadcap.util.Debug;

/**
 * An input stream attached to a <code>RandomAccess</code> object.
 *
 * @author Stan Bailes
 */
public class RandomAccessInputStream extends InputStream {
    RandomAccess                        ra;
    int                                 position;
    byte[]                              buf1 = new byte[1];
    
    public RandomAccessInputStream(RandomAccess ra) {
        this.ra = ra;
        this.position = 0;
    }

    public int getPosition() { return position; }
    public void setPosition(int p) { position = p; }

    /**
     * Reads the next byte of data from this input stream. The value 
     * byte is returned as an <code>int</code> in the range 
     * <code>0</code> to <code>255</code>. If no byte is available 
     * because the end of the stream has been reached, the value 
     * <code>-1</code> is returned.
     *
     * @return     the next byte of data, or <code>-1</code> if the end of the
     *             stream is reached.
     * @exception  IOException  if an I/O error occurs.
     */
    public int read() throws IOException {
        if (position >= ra.size()) return -1;

        ra.read(position, buf1, 0, 1);
        position++;
        return buf1[0] & 0xff;
    }

    /**
     * Reads up to <code>len</code> bytes of data from this input stream 
     * into an array of bytes. This method blocks until some input is 
     * available. If the first argument is <code>null,</code> up to 
     * <code>len</code> bytes are read and discarded. 
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset of the data.
     * @param      len   the maximum number of bytes read.
     * @return     the total number of bytes read into the buffer, or
     *             <code>-1</code> if there is no more data because the end of
     *             the stream has been reached.
     * @exception  IOException  if an I/O error occurs.
     */
    public int read(byte b[], int off, int len) throws IOException {
        if (position >= ra.size()) return -1;
        if (ra.size() - position < len) len = (int)(ra.size() - position);

        if (b != null) ra.read(position, b, off, len);
        position += len;
        return len;
    }

    /**
     * Skips over and discards <code>n</code> bytes of data from this 
     * input stream. The <code>skip</code> method may, for a variety of 
     * reasons, end up skipping over some smaller number of bytes, 
     * possibly <code>0</code>. The actual number of bytes skipped is 
     * returned. 
     * <p>
     * The <code>skip</code> method of <code>InputStream</code> creates 
     * a byte array of length <code>n</code> and then reads into it until 
     * <code>n</code> bytes have been read or the end of the stream has 
     * been reached. Subclasses are encouraged to provide a more 
     * efficient implementation of this method. 
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @exception  IOException  if an I/O error occurs.
     * @since      JDK1.0
     */
    public long skip(long n) throws IOException {
        return read(null, 0, (int)n);
    }

    /**
     * Returns the number of bytes that can be read from this input 
     * stream without blocking. The available method of 
     * <code>InputStream</code> returns <code>0</code>. This method 
     * <B>should</B> be overridden by subclasses. 
     *
     * @return     the number of bytes that can be read from this input stream
     *             without blocking.
     * @exception  IOException  if an I/O error occurs.
     */
    public int available() throws IOException {
        return (int)(ra.size() - position);
    }

    /**
     * Closes this input stream and releases any system resources 
     * associated with the stream. 
     *
     * @exception  IOException  if an I/O error occurs.
     */
    public void close() throws IOException {
        ra.close();
    }

}