ImageInputStreamImpl2.java

/*
 * @(#)ImageInputStreamImpl2.java 
 * 
 * Copyright (c) 2011 Werner Randelshofer, Immensee, Switzerland.
 * All rights reserved.
 * 
 * You may not use, copy or modify this file, except in compliance with the
 * license agreement you entered into with Werner Randelshofer.
 * For details see accompanying license terms.
 */
package ch.randelshofer.media.io;

import java.io.IOException;
import java.nio.ByteOrder;
import javax.imageio.stream.ImageInputStreamImpl;

/**
 * {@code ImageInputStreamImpl2} fixes bugs in ImageInputStreamImpl.
 * <p>
 * ImageInputStreamImpl uses read(byte[]) instead of readFully(byte[]) inside of
 * readShort. This results in corrupt data input if the underlying stream can
 * not fulfill the read operation in a single step.
 *
 * @author Werner Randelshofer
 * @version $Id: ImageInputStreamImpl2.java 134 2011-12-02 16:23:00Z werner $
 */
public abstract class ImageInputStreamImpl2 extends ImageInputStreamImpl {
    // Length of the buffer used for readFully(type[], int, int)
    private static final int BYTE_BUF_LENGTH = 8192;
    /**
     * Byte buffer used for readFully(type[], int, int).  Note that this
     * array is also used for bulk reads in readShort(), readInt(), etc, so
     * it should be large enough to hold a primitive value (i.e. >= 8 bytes).
     * Also note that this array is package protected, so that it can be
     * used by ImageOutputStreamImpl in a similar manner.
     */
    byte[] byteBuf = new byte[BYTE_BUF_LENGTH];

    @Override
        public short readShort() throws IOException {
        readFully(byteBuf, 0, 2);

        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            return (short)
                (((byteBuf[0] & 0xff) << 8) | ((byteBuf[1] & 0xff) << 0));
        } else {
            return (short)
                (((byteBuf[1] & 0xff) << 8) | ((byteBuf[0] & 0xff) << 0));
        }
    }
    public int readInt() throws IOException {
        readFully(byteBuf, 0, 4);

        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            return
                (((byteBuf[0] & 0xff) << 24) | ((byteBuf[1] & 0xff) << 16) |
                 ((byteBuf[2] & 0xff) <<  8) | ((byteBuf[3] & 0xff) <<  0));
        } else {
            return
                (((byteBuf[3] & 0xff) << 24) | ((byteBuf[2] & 0xff) << 16) |
                 ((byteBuf[1] & 0xff) <<  8) | ((byteBuf[0] & 0xff) <<  0));
        }
    }

}