sharedfileinputstream.java

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	    len = (int)(datalen - (bufpos - start + pos));
	int n = in.read(buf, pos, len);
        if (n > 0)
            count = n + pos;
    }

    /**
     * See the general contract of the <code>read</code>
     * method of <code>InputStream</code>.
     *
     * @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 synchronized int read() throws IOException {
        ensureOpen();
	if (pos >= count) {
	    fill();
	    if (pos >= count)
		return -1;
	}
	return buf[pos++] & 0xff;
    }

    /**
     * Read characters into a portion of an array, reading from the underlying
     * stream at most once if necessary.
     */
    private int read1(byte[] b, int off, int len) throws IOException {
	int avail = count - pos;
	if (avail <= 0) {
	    if (false) {
	    /* If the requested length is at least as large as the buffer, and
	       if there is no mark/reset activity, do not bother to copy the
	       bytes into the local buffer.  In this way buffered streams will
	       cascade harmlessly. */
	    if (len >= buf.length && markpos < 0) {
		// XXX - seek, update bufpos - how?
		return in.read(b, off, len);
	    }
	    }
	    fill();
	    avail = count - pos;
	    if (avail <= 0) return -1;
	}
	int cnt = (avail < len) ? avail : len;
	System.arraycopy(buf, pos, b, off, cnt);
	pos += cnt;
	return cnt;
    }

    /**
     * Reads bytes from this stream into the specified byte array,
     * starting at the given offset.
     *
     * <p> This method implements the general contract of the corresponding
     * <code>{@link java.io.InputStream#read(byte[], int, int) read}</code>
     * method of the <code>{@link java.io.InputStream}</code> class.
     *
     * @param      b     destination buffer.
     * @param      off   offset at which to start storing bytes.
     * @param      len   maximum number of bytes to read.
     * @return     the number of bytes read, or <code>-1</code> if the end of
     *             the stream has been reached.
     * @exception  IOException  if an I/O error occurs.
     */
    public synchronized int read(byte b[], int off, int len)
	throws IOException
    {
        ensureOpen();
        if ((off | len | (off + len) | (b.length - (off + len))) < 0) {
	    throw new IndexOutOfBoundsException();
	} else if (len == 0) {
	    return 0;
	}

	int n = read1(b, off, len);
	if (n <= 0) return n;
	while ((n < len) /* && (in.available() > 0) */) {
	    int n1 = read1(b, off + n, len - n);
	    if (n1 <= 0) break;
	    n += n1;
	}
	return n;
    }

    /**
     * See the general contract of the <code>skip</code>
     * method of <code>InputStream</code>.
     *
     * @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 synchronized long skip(long n) throws IOException {
        ensureOpen();
	if (n <= 0) {
	    return 0;
	}
	long avail = count - pos;
     
        if (avail <= 0) {
            // If no mark position set then don't keep in buffer
	    /*
            if (markpos <0) 
                return in.skip(n);
	    */
            
            // Fill in buffer to save bytes for reset
            fill();
            avail = count - pos;
            if (avail <= 0)
                return 0;
        }
        
        long skipped = (avail < n) ? avail : n;
        pos += skipped;
        return skipped;
    }

    /**
     * Returns the number of bytes that can be read from this input 
     * stream without blocking. 
     *
     * @return     the number of bytes that can be read from this input
     *             stream without blocking.
     * @exception  IOException  if an I/O error occurs.
     */
    public synchronized int available() throws IOException {
        ensureOpen();
	return (count - pos) + in_available();
    }

    private int in_available() throws IOException {
	// XXX - overflow
	return (int)((start + datalen) - (bufpos + count));
    }

    /** 
     * See the general contract of the <code>mark</code>
     * method of <code>InputStream</code>.
     *
     * @param   readlimit   the maximum limit of bytes that can be read before
     *                      the mark position becomes invalid.
     * @see     #reset()
     */
    public synchronized void mark(int readlimit) {
	marklimit = readlimit;
	markpos = pos;
    }

    /**
     * See the general contract of the <code>reset</code>
     * method of <code>InputStream</code>.
     * <p>
     * If <code>markpos</code> is <code>-1</code>
     * (no mark has been set or the mark has been
     * invalidated), an <code>IOException</code>
     * is thrown. Otherwise, <code>pos</code> is
     * set equal to <code>markpos</code>.
     *
     * @exception  IOException  if this stream has not been marked or
     *               if the mark has been invalidated.
     * @see        #mark(int)
     */
    public synchronized void reset() throws IOException {
        ensureOpen();
	if (markpos < 0)
	    throw new IOException("Resetting to invalid mark");
	pos = markpos;
    }

    /**
     * Tests if this input stream supports the <code>mark</code> 
     * and <code>reset</code> methods. The <code>markSupported</code> 
     * method of <code>SharedFileInputStream</code> returns 
     * <code>true</code>. 
     *
     * @return  a <code>boolean</code> indicating if this stream type supports
     *          the <code>mark</code> and <code>reset</code> methods.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.InputStream#reset()
     */
    public boolean markSupported() {
	return true;
    }

    /**
     * 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 {
        if (in == null)
            return;
	try {
	    if (master)
		sf.forceClose();
	    else
		sf.close();
	} finally {
	    sf = null;
	    in = null;
	    buf = null;
	}
    }

    /**
     * Return the current position in the InputStream, as an
     * offset from the beginning of the InputStream.
     *
     * @return  the current position
     */
    public long getPosition() {
//System.out.println("getPosition: start " + start + " pos " + pos + " bufpos " + bufpos + " = " + (bufpos + pos - start));
	if (in == null)
	    throw new RuntimeException("Stream closed");
	return bufpos + pos - start;
    }

    /**
     * Return a new InputStream representing a subset of the data
     * from this InputStream, starting at <code>start</code> (inclusive)
     * up to <code>end</code> (exclusive).  <code>start</code> must be
     * non-negative.  If <code>end</code> is -1, the new stream ends
     * at the same place as this stream.  The returned InputStream
     * will also implement the SharedInputStream interface.
     *
     * @param	start	the starting position
     * @param	end	the ending position + 1
     * @return		the new stream
     */
    public InputStream newStream(long start, long end) {
	if (in == null)
	    throw new RuntimeException("Stream closed");
	if (start < 0)
	    throw new IllegalArgumentException("start < 0");
	if (end == -1)
	    end = datalen;
	return new SharedFileInputStream(sf,
			this.start + (int)start, (int)(end - start), bufsize);
    }

    // for testing...
    /*
    public static void main(String[] argv) throws Exception {
	SharedFileInputStream is = new SharedFileInputStream(argv[0]);
	java.util.Random r = new java.util.Random();
	int b;
	while ((b = is.read()) >= 0) {
	    System.out.write(b);
	    if (r.nextDouble() < 0.3) {
		InputStream is2 = is.newStream(is.getPosition(), -1);
		int b2;
		while ((b2 = is2.read()) >= 0)
		    ;
	    }
	}
    }
    */

    /**
     * Force this stream to close.
     */
    protected void finalize() throws Throwable {
	super.finalize();
	close();
    }
}