/*

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */
package org.apache.batik.ext.awt.image.codec.util;

import java.io.DataInput;
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.UTFDataFormatException;

/**
 * An abstract subclass of <code>java.io.InputStream</code> that allows seeking
 * within the input, similar to the <code>RandomAccessFile</code> class.
 * Additionally, the <code>DataInput</code> interface is supported and extended
 * to include support for little-endian representations of fundamental data
 * types.
 *
 * <p> In addition to the familiar methods from <code>InputStream</code>, the
 * methods <code>getFilePointer()</code>, <code>seek()</code>, are defined as in
 * the <code>RandomAccessFile</code> class.  The <code>canSeekBackwards()</code>
 * method will return <code>true</code> if it is permissible to seek to a
 * position earlier in the stream than the current value of
 * <code>getFilePointer()</code>.  Some subclasses of
 * <code>SeekableStream</code> guarantee the ability to seek backwards while
 * others may not offer this feature in the interest of providing greater
 * efficiency for those users who do not require it.
 *
 * <p> The <code>DataInput</code> interface is supported as well.  This included
 * the <code>skipBytes()</code> and <code>readFully()</code> methods and a
 * variety of <code>read</code> methods for various data types.
 *
 * <p> A number of concrete subclasses of <code>SeekableStream</code> are
 * supplied in the <code>com.sun.media.jai.codec</code> package.
 *
 * <p> Three classes are provided for the purpose of adapting a standard
 * <code>InputStream</code> to the <code>SeekableStream</code> interface.
 * <code>ForwardSeekableStream</code> does not allows seeking backwards, but is
 * inexpensive to use.  <code>FileCacheSeekableStream</code> maintains a copy of
 * all of the data read from the input in a temporary file; this file will be
 * discarded automatically when the <code>FileSeekableStream</code> is
 * finalized, or when the JVM exits normally.
 * <code>FileCacheSeekableStream</code> is intended to be reasonably efficient
 * apart from the unavoidable use of disk space.  In circumstances where the
 * creation of a temporary file is not possible,
 * <code>MemoryCacheSeekableStream</code> may be used.
 * <code>MemoryCacheSeekableStream</code> creates a potentially large in-memory
 * buffer to store the stream data and so should be avoided when possible.
 *
 * <p> The <code>FileSeekableStream</code> class wraps a <code>File</code> or
 * <code>RandomAccessFile</code>. It forwards requests to the real underlying
 * file.  It performs a limited amount of caching in order to avoid excessive
 * I/O costs.
 *
 * <p> The <code>SegmentedSeekableStream</code> class performs a different sort
 * of function.  It creates a <code>SeekableStream</code> from another
 * <code>SeekableStream</code> by selecting a series of portions or "segments".
 * Each segment starts at a specified location within the source
 * <code>SeekableStream</code> and extends for a specified number of bytes.  The
 * <code>StreamSegmentMapper</code> interface and <code>StreamSegment</code>
 * class may be used to compute the segment positions dynamically.
 *
 * <p> A convenience methods, <code>wrapInputStream</code> is provided to
 * construct a suitable <code>SeekableStream</code> instance whose data is
 * supplied by a given <code>InputStream</code>.  The caller, by means of the
 * <code>canSeekBackwards</code> parameter, determines whether support for
 * seeking backwards is required.
 *
 * @version $Id: SeekableStream.java 522271 2007-03-25 14:42:45Z dvholten $
 */
public abstract class SeekableStream extends InputStream implements DataInput {

    /**
     * Returns a <code>SeekableStream</code> that will read from a
     * given <code>InputStream</code>, optionally including support
     * for seeking backwards.  This is a convenience method that
     * avoids the need to instantiate specific subclasses of
     * <code>SeekableStream</code> depending on the current security
     * model.
     *
     * @param is An <code>InputStream</code>.
     * @param canSeekBackwards <code>true</code> if the ability to seek
     *        backwards in the output is required.
     * @return An instance of <code>SeekableStream</code>.
     */
    public static SeekableStream wrapInputStream(InputStream is,
                                                 boolean canSeekBackwards) {
        SeekableStream stream = null;

        if (canSeekBackwards) {
            try {
                stream = new FileCacheSeekableStream(is);
            } catch (Exception e) {
                stream = new MemoryCacheSeekableStream(is);
            }
        } else {
            stream = new ForwardSeekableStream(is);
        }
        return stream;
    }

    // Methods from InputStream

    /**
     * Reads the next byte of data from the 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. This method
     * blocks until input data is available, the end of the stream is detected,
     * or an exception is thrown.
     *
     * <p> A subclass must provide an implementation of this method.
     *
     * @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 abstract int read() throws IOException;

    /**
     * Reads up to <code>len</code> bytes of data from the input stream into
     * an array of bytes.  An attempt is made to read as many as
     * <code>len</code> bytes, but a smaller number may be read, possibly
     * zero. The number of bytes actually read is returned as an integer.
     *
     * <p> This method blocks until input data is available, end of stream is
     * detected, or an exception is thrown.
     *
     * <p> If <code>b</code> is <code>null</code>, a
     * <code>NullPointerException</code> is thrown.
     *
     * <p> If <code>off</code> is negative, or <code>len</code> is negative, or
     * <code>off+len</code> is greater than the length of the array
     * <code>b</code>, then an <code>IndexOutOfBoundsException</code> is
     * thrown.
     *
     * <p> If <code>len</code> is zero, then no bytes are read and
     * <code>0</code> is returned; otherwise, there is an attempt to read at
     * least one byte. If no byte is available because the stream is at end of
     * stream, the value <code>-1</code> is returned; otherwise, at least one
     * byte is read and stored into <code>b</code>.
     *
     * <p> The first byte read is stored into element <code>b[off]</code>, the
     * next one into <code>b[off+1]</code>, and so on. The number of bytes read
     * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
     * bytes actually read; these bytes will be stored in elements
     * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
     * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
     * <code>b[off+len-1]</code> unaffected.
     *
     * <p> In every case, elements <code>b[0]</code> through
     * <code>b[off]</code> and elements <code>b[off+len]</code> through
     * <code>b[b.length-1]</code> are unaffected.
     *
     * <p> If the first byte cannot be read for any reason other than end of
     * stream, then an <code>IOException</code> is thrown. In particular, an
     * <code>IOException</code> is thrown if the input stream has been closed.
     *
     * <p> A subclass must provide an implementation of this method.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset in array <code>b</code>
     *                   at which the data is written.
     * @param      len   the maximum number of bytes to 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 abstract int read(byte[] b, int off, int len) throws IOException;

    // Implemented in InputStream:
    //
    // public int read(byte[] b) throws IOException {
    // public long skip(long n) throws IOException
    // public int available) throws IOException
    // public void close() throws IOException;

    /** Marked position, shared by {@link ForwardSeekableStream} */
    protected long markPos = -1L;

    /**
     * Marks the current file position for later return using
     * the <code>reset()</code> method.
     */
    public synchronized void mark(int readLimit) {
        try {
            markPos = getFilePointer();
        } catch (IOException e) {
            markPos = -1L;
        }
    }

    /**
     * Returns the file position to its position at the time of
     * the immediately previous call to the <code>mark()</code>
     * method.
     */
    public synchronized void reset() throws IOException {
        if (markPos != -1) {
            seek(markPos);
        }
    }

    /**
     * Returns <code>true</code> if marking is supported.
     * Marking is automatically supported for <code>SeekableStream</code>
     * subclasses that support seeking backeards.  Subclasses that do
     * not support seeking backwards but do support marking must override
     * this method.
     */
    public boolean markSupported() {
        return canSeekBackwards();
    }

    /**
     * Returns <code>true</code> if this object supports calls to
     * <code>seek(pos)</code> with an offset <code>pos</code> smaller
     * than the current offset, as returned by <code>getFilePointer</code>.
     */
    public boolean canSeekBackwards() {
        return false;
    }

    /**
     * Returns the current offset in this stream.
     *
     * @return     the offset from the beginning of the stream, in bytes,
     *             at which the next read occurs.
     * @exception  IOException  if an I/O error occurs.
     */
    public abstract long getFilePointer() throws IOException;

    /**
     * Sets the offset, measured from the beginning of this
     * stream, at which the next read occurs.
     *
     * <p> If <code>canSeekBackwards()</code> returns <code>false</code>,
     * then setting <code>pos</code> to an offset smaller than
     * the current value of <code>getFilePointer()</code> will have
     * no effect.
     *
     * @param      pos   the offset position, measured in bytes from the
     *                   beginning of the stream, at which to set the stream
     *                   pointer.
     * @exception  IOException  if <code>pos</code> is less than
     *                          <code>0</code> or if an I/O error occurs.
     */
    public abstract void seek(long pos) throws IOException;

    // Methods from RandomAccessFile

    /**
     * Reads <code>b.length</code> bytes from this stream into the byte
     * array, starting at the current stream pointer. This method reads
     * repeatedly from the stream until the requested number of bytes are
     * read. This method blocks until the requested number of bytes are
     * read, the end of the stream is detected, or an exception is thrown.
     *
     * @param      b   the buffer into which the data is read.
     * @exception  EOFException  if this stream reaches the end before reading
     *               all the bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final void readFully(byte[] b) throws IOException {
        readFully(b, 0, b.length);
    }

    /**
     * Reads exactly <code>len</code> bytes from this stream into the byte
     * array, starting at the current stream pointer. This method reads
     * repeatedly from the stream until the requested number of bytes are
     * read. This method blocks until the requested number of bytes are
     * read, the end of the stream is detected, or an exception is thrown.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset of the data.
     * @param      len   the number of bytes to read.
     * @exception  EOFException  if this stream reaches the end before reading
     *               all the bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final void readFully(byte[] b, int off, int len)
        throws IOException {
        int n = 0;
        do {
            int count = this.read(b, off + n, len - n);
            if (count < 0)
                throw new EOFException();
            n += count;
        } while (n < len);
    }

    // Methods from DataInput, plus little-endian versions

    /**
     * Attempts to skip over <code>n</code> bytes of input discarding the
     * skipped bytes.
     * <p>
     *
     * This method may skip over some smaller number of bytes, possibly zero.
     * This may result from any of a number of conditions; reaching end of
     * stream before <code>n</code> bytes have been skipped is only one
     * possibility. This method never throws an <code>EOFException</code>.
     * The actual number of bytes skipped is returned.  If <code>n</code>
     * is negative, no bytes are skipped.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @exception  IOException  if an I/O error occurs.
     */
    public int skipBytes(int n) throws IOException {
        if (n <= 0) {
            return 0;
        }
        return (int)skip(n);
    }

    /**
     * Reads a <code>boolean</code> from this stream. This method reads a
     * single byte from the stream, starting at the current stream pointer.
     * A value of <code>0</code> represents
     * <code>false</code>. Any other value represents <code>true</code>.
     * This method blocks until the byte is read, the end of the stream
     * is detected, or an exception is thrown.
     *
     * @return     the <code>boolean</code> value read.
     * @exception  EOFException  if this stream has reached the end.
     * @exception  IOException   if an I/O error occurs.
     */
    public final boolean readBoolean() throws IOException {
        int ch = this.read();
        if (ch < 0)
            throw new EOFException();
        return (ch != 0);
    }

    /**
     * Reads a signed eight-bit value from this stream. This method reads a
     * byte from the stream, starting from the current stream pointer.
     * If the byte read is <code>b</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
     * then the result is:
     * <blockquote><pre>
     *     (byte)(b)
     * </pre></blockquote>
     * <p>
     * This method blocks until the byte is read, the end of the stream
     * is detected, or an exception is thrown.
     *
     * @return     the next byte of this stream as a signed eight-bit
     *             <code>byte</code>.
     * @exception  EOFException  if this stream has reached the end.
     * @exception  IOException   if an I/O error occurs.
     */
    public final byte readByte() throws IOException {
        int ch = this.read();
        if (ch < 0)
            throw new EOFException();
        return (byte)(ch);
    }

    /**
     * Reads an unsigned eight-bit number from this stream. This method reads
     * a byte from this stream, starting at the current stream pointer,
     * and returns that byte.
     * <p>
     * This method blocks until the byte is read, the end of the stream
     * is detected, or an exception is thrown.
     *
     * @return     the next byte of this stream, interpreted as an unsigned
     *             eight-bit number.
     * @exception  EOFException  if this stream has reached the end.
     * @exception  IOException   if an I/O error occurs.
     */
    public final int readUnsignedByte() throws IOException {
        int ch = this.read();
        if (ch < 0)
            throw new EOFException();
        return ch;
    }

    /**
     * Reads a signed 16-bit number from this stream.
     * The method reads two
     * bytes from this stream, starting at the current stream pointer.
     * If the two bytes read, in order, are
     * <code>b1</code> and <code>b2</code>, where each of the two values is
     * between <code>0</code> and <code>255</code>, inclusive, then the
     * result is equal to:
     * <blockquote><pre>
     *     (short)((b1 &lt;&lt; 8) | b2)
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this stream, interpreted as a signed
     *             16-bit number.
     * @exception  EOFException  if this stream reaches the end before reading
     *               two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final short readShort() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (short)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * Reads a signed 16-bit number from this stream in little-endian order.
     * The method reads two
     * bytes from this stream, starting at the current stream pointer.
     * If the two bytes read, in order, are
     * <code>b1</code> and <code>b2</code>, where each of the two values is
     * between <code>0</code> and <code>255</code>, inclusive, then the
     * result is equal to:
     * <blockquote><pre>
     *     (short)((b2 &lt;&lt; 8) | b1)
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this stream, interpreted as a signed
     *             16-bit number.
     * @exception  EOFException  if this stream reaches the end before reading
     *               two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final short readShortLE() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (short)((ch2 << 8) + (ch1 << 0));
    }

    /**
     * Reads an unsigned 16-bit number from this stream. This method reads
     * two bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are
     * <code>b1</code> and <code>b2</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (b1 &lt;&lt; 8) | b2
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this stream, interpreted as an
     *             unsigned 16-bit integer.
     * @exception  EOFException  if this stream reaches the end before reading
     *             two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final int readUnsignedShort() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (ch1 << 8) + (ch2 << 0);
    }

    /**
     * Reads an unsigned 16-bit number from this stream in little-endian order.
     * This method reads
     * two bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are
     * <code>b1</code> and <code>b2</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (b2 &lt;&lt; 8) | b1
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this stream, interpreted as an
     *             unsigned 16-bit integer.
     * @exception  EOFException  if this stream reaches the end before reading
     *               two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final int readUnsignedShortLE() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (ch2 << 8) + (ch1 << 0);
    }

    /**
     * Reads a Unicode character from this stream. This method reads two
     * bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are
     * <code>b1</code> and <code>b2</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (char)((b1 &lt;&lt; 8) | b2)
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this stream as a Unicode character.
     * @exception  EOFException  if this stream reaches the end before reading
     *               two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final char readChar() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (char)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * Reads a Unicode character from this stream in little-endian order.
     * This method reads two
     * bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are
     * <code>b1</code> and <code>b2</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (char)((b2 &lt;&lt; 8) | b1)
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this stream as a Unicode character.
     * @exception  EOFException  if this stream reaches the end before reading
     *               two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final char readCharLE() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (char)((ch2 << 8) + (ch1 << 0));
    }

    /**
     * Reads a signed 32-bit integer from this stream. This method reads 4
     * bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are <code>b1</code>,
     * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
     * </pre></blockquote>
     * <p>
     * This method blocks until the four bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next four bytes of this stream, interpreted as an
     *             <code>int</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *               four bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final int readInt() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        int ch3 = this.read();
        int ch4 = this.read();
        if ((ch1 | ch2 | ch3 | ch4) < 0)
            throw new EOFException();
        return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
    }

    /**
     * Reads a signed 32-bit integer from this stream in little-endian order.
     * This method reads 4
     * bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are <code>b1</code>,
     * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (b4 &lt;&lt; 24) | (b3 &lt;&lt; 16) + (b2 &lt;&lt; 8) + b1
     * </pre></blockquote>
     * <p>
     * This method blocks until the four bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next four bytes of this stream, interpreted as an
     *             <code>int</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *               four bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final int readIntLE() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        int ch3 = this.read();
        int ch4 = this.read();
        if ((ch1 | ch2 | ch3 | ch4) < 0)
            throw new EOFException();
        return ((ch4 << 24) + (ch3 << 16) + (ch2 << 8) + (ch1 << 0));
    }

    /**
     * Reads an unsigned 32-bit integer from this stream. This method reads 4
     * bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are <code>b1</code>,
     * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
     * </pre></blockquote>
     * <p>
     * This method blocks until the four bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next four bytes of this stream, interpreted as a
     *             <code>long</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *               four bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final long readUnsignedInt() throws IOException {
        long ch1 = this.read();
        long ch2 = this.read();
        long ch3 = this.read();
        long ch4 = this.read();
        if ((ch1 | ch2 | ch3 | ch4) < 0)
            throw new EOFException();
        return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
    }

    private byte[] ruileBuf = new byte[4];

    /**
     * Reads an unsigned 32-bit integer from this stream in little-endian
     * order.  This method reads 4
     * bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are <code>b1</code>,
     * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where
     * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (b4 &lt;&lt; 24) | (b3 &lt;&lt; 16) + (b2 &lt;&lt; 8) + b1
     * </pre></blockquote>
     * <p>
     * This method blocks until the four bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next four bytes of this stream, interpreted as a
     *             <code>long</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *               four bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final long readUnsignedIntLE() throws IOException {
        this.readFully(ruileBuf);
        long ch1 = (ruileBuf[0] & 0xff);
        long ch2 = (ruileBuf[1] & 0xff);
        long ch3 = (ruileBuf[2] & 0xff);
        long ch4 = (ruileBuf[3] & 0xff);

        return ((ch4 << 24) + (ch3 << 16) + (ch2 << 8) + (ch1 << 0));
    }

    /**
     * Reads a signed 64-bit integer from this stream. This method reads eight
     * bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are
     * <code>b1</code>, <code>b2</code>, <code>b3</code>,
     * <code>b4</code>, <code>b5</code>, <code>b6</code>,
     * <code>b7</code>, and <code>b8,</code> where:
     * <blockquote><pre>
     *     0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
     * </pre></blockquote>
     * <p>
     * then the result is equal to:
     * <p><blockquote><pre>
     *     ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
     *     + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
     *     + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
     *     + ((long)b7 &lt;&lt; 8) + b8
     * </pre></blockquote>
     * <p>
     * This method blocks until the eight bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next eight bytes of this stream, interpreted as a
     *             <code>long</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *               eight bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final long readLong() throws IOException {
        return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
    }

    /**
     * Reads a signed 64-bit integer from this stream in little-endian
     * order. This method reads eight
     * bytes from the stream, starting at the current stream pointer.
     * If the bytes read, in order, are
     * <code>b1</code>, <code>b2</code>, <code>b3</code>,
     * <code>b4</code>, <code>b5</code>, <code>b6</code>,
     * <code>b7</code>, and <code>b8,</code> where:
     * <blockquote><pre>
     *     0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
     * </pre></blockquote>
     * <p>
     * then the result is equal to:
     * <p><blockquote><pre>
     *     ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
     *     + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
     *     + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
     *     + ((long)b7 &lt;&lt; 8) + b8
     * </pre></blockquote>
     * <p>
     * This method blocks until the eight bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next eight bytes of this stream, interpreted as a
     *             <code>long</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *               eight bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final long readLongLE() throws IOException {
        int i1 = readIntLE();
        int i2 = readIntLE();
        return ((long)i2 << 32) + (i1 & 0xFFFFFFFFL);
    }

    /**
     * Reads a <code>float</code> from this stream. This method reads an
     * <code>int</code> value, starting at the current stream pointer,
     * as if by the <code>readInt</code> method
     * and then converts that <code>int</code> to a <code>float</code>
     * using the <code>intBitsToFloat</code> method in class
     * <code>Float</code>.
     * <p>
     * This method blocks until the four bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next four bytes of this stream, interpreted as a
     *             <code>float</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *             four bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final float readFloat() throws IOException {
        return Float.intBitsToFloat(readInt());
    }

    /**
     * Reads a <code>float</code> from this stream in little-endian order.
     * This method reads an
     * <code>int</code> value, starting at the current stream pointer,
     * as if by the <code>readInt</code> method
     * and then converts that <code>int</code> to a <code>float</code>
     * using the <code>intBitsToFloat</code> method in class
     * <code>Float</code>.
     * <p>
     * This method blocks until the four bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next four bytes of this stream, interpreted as a
     *             <code>float</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *             four bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final float readFloatLE() throws IOException {
        return Float.intBitsToFloat(readIntLE());
    }

    /**
     * Reads a <code>double</code> from this stream. This method reads a
     * <code>long</code> value, starting at the current stream pointer,
     * as if by the <code>readLong</code> method
     * and then converts that <code>long</code> to a <code>double</code>
     * using the <code>longBitsToDouble</code> method in
     * class <code>Double</code>.
     * <p>
     * This method blocks until the eight bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next eight bytes of this stream, interpreted as a
     *             <code>double</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *             eight bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final double readDouble() throws IOException {
        return Double.longBitsToDouble(readLong());
    }

    /**
     * Reads a <code>double</code> from this stream in little-endian order.
     * This method reads a
     * <code>long</code> value, starting at the current stream pointer,
     * as if by the <code>readLong</code> method
     * and then converts that <code>long</code> to a <code>double</code>
     * using the <code>longBitsToDouble</code> method in
     * class <code>Double</code>.
     * <p>
     * This method blocks until the eight bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next eight bytes of this stream, interpreted as a
     *             <code>double</code>.
     * @exception  EOFException  if this stream reaches the end before reading
     *             eight bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final double readDoubleLE() throws IOException {
        return Double.longBitsToDouble(readLongLE());
    }

    /**
     * Reads the next line of text from this stream.  This method successively
     * reads bytes from the stream, starting at the current stream pointer,
     * until it reaches a line terminator or the end
     * of the stream.  Each byte is converted into a character by taking the
     * byte's value for the lower eight bits of the character and setting the
     * high eight bits of the character to zero.  This method does not,
     * therefore, support the full Unicode character set.
     *
     * <p> A line of text is terminated by a carriage-return character
     * (<code>'&#92;r'</code>), a newline character (<code>'&#92;n'</code>), a
     * carriage-return character immediately followed by a newline character,
     * or the end of the stream.  Line-terminating characters are discarded and
     * are not included as part of the string returned.
     *
     * <p> This method blocks until a newline character is read, a carriage
     * return and the byte following it are read (to see if it is a newline),
     * the end of the stream is reached, or an exception is thrown.
     *
     * @return     the next line of text from this stream, or null if end
     *             of stream is encountered before even one byte is read.
     * @exception  IOException  if an I/O error occurs.
     */
    public final String readLine() throws IOException {
        StringBuffer input = new StringBuffer();
        int c = -1;
        boolean eol = false;

        while (!eol) {
            switch (c = read()) {
            case -1:
            case '\n':
                eol = true;
                break;
            case '\r':
                eol = true;
                long cur = getFilePointer();
                if ((read()) != '\n') {
                    seek(cur);
                }
                break;
            default:
                input.append((char)c);
                break;
            }
        }

        if ((c == -1) && (input.length() == 0)) {
            return null;
        }
        return input.toString();
    }

    /**
     * Reads in a string from this stream. The string has been encoded
     * using a modified UTF-8 format.
     * <p>
     * The first two bytes are read, starting from the current stream
     * pointer, as if by
     * <code>readUnsignedShort</code>. This value gives the number of
     * following bytes that are in the encoded string, not
     * the length of the resulting string. The following bytes are then
     * interpreted as bytes encoding characters in the UTF-8 format
     * and are converted into characters.
     * <p>
     * This method blocks until all the bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     a Unicode string.
     * @exception  EOFException            if this stream reaches the end before
     *               reading all the bytes.
     * @exception  IOException             if an I/O error occurs.
     * @exception  UTFDataFormatException  if the bytes do not represent
     *               valid UTF-8 encoding of a Unicode string.
     */
    public final String readUTF() throws IOException {
        return DataInputStream.readUTF(this);
    }

    /**
     * Releases any system resources associated with this stream
     * by calling the <code>close()</code> method.
     */
    protected void finalize() throws Throwable {
        super.finalize();
        close();
    }
}
