/**
 * Copyright (c) 2001 Alexander V. Konstantinou (akonstan@acm.org)
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Alexander V. Konstantinou makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

import java.io.*;
import javax.net.ssl.*;

/**
 * Registers the last read() operation with SecureRMISocketFactory
 *
 * @see SecureRMISocketFactory#setLocalThreadLastReadSocket(SSLSocket)
 *
 * @version $Revision: 1.1 $ ; $Date: 2001/12/10 20:43:27 $
 * @author Alexander V. Konstantinou (akonstan@acm.org)   
 */
public class InputStreamMonitor extends InputStream {
  
  /** Wrapped input stream */
  protected final InputStream istream;

  /** Input stream SSL socket source */
  protected final SSLSocket socket;

  /**
   * Wrap the input stream generated from the specified SSL socket
   */
  public InputStreamMonitor(InputStream istream, SSLSocket socket) {
    this.istream = istream;
    this.socket = socket;
  }

  /**
   * 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 int read() throws IOException {
    SecureRMISocketFactory.setLocalThreadLastReadSocket(socket);
    return(istream.read());
  }
    
  /**
   * Reads some number of bytes from the input stream and stores them into
   * the buffer array <code>b</code>. The number of bytes actually read is
   * returned as an integer.  This method blocks until input data is
   * available, end of file is detected, or an exception is thrown.
   *
   * <p> If <code>b</code> is <code>null</code>, a
   * <code>NullPointerException</code> is thrown.  If the length of
   * <code>b</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 file, 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[0]</code>, the
   * next one into <code>b[1]</code>, and so on. The number of bytes read is,
   * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
   * number of bytes actually read; these bytes will be stored in elements
   * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
   * leaving elements <code>b[</code><i>k</i><code>]</code> through
   * <code>b[b.length-1]</code> unaffected.
   *
   * <p> If the first byte cannot be read for any reason other than end of
   * file, then an <code>IOException</code> is thrown. In particular, an
   * <code>IOException</code> is thrown if the input stream has been closed.
   *
   * <p> The <code>read(b)</code> method for class <code>InputStream</code>
   * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
   *
   * @param      b   the buffer into which the data is read.
   * @return     the total number of bytes read into the buffer, or
   *             <code>-1</code> is there is no more data because the end of
   *             the stream has been reached.
   * @exception  IOException  if an I/O error occurs.
   * @see        java.io.InputStream#read(byte[], int, int)
   */
  public int read(byte b[]) throws IOException {
    SecureRMISocketFactory.setLocalThreadLastReadSocket(socket);
    return(istream.read(b));
  }

  /**
   * 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 file 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
   * file, 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
   * file, then an <code>IOException</code> is thrown. In particular, an
   * <code>IOException</code> is thrown if the input stream has been closed.
   *
   * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
   * for class <code>InputStream</code> simply calls the method
   * <code>read()</code> repeatedly. If the first such call results in an
   * <code>IOException</code>, that exception is returned from the call to
   * the <code>read(b,</code> <code>off,</code> <code>len)</code> method.  If
   * any subsequent call to <code>read()</code> results in a
   * <code>IOException</code>, the exception is caught and treated as if it
   * were end of file; the bytes read up to that point are stored into
   * <code>b</code> and the number of bytes read before the exception
   * occurred is returned.  Subclasses are encouraged to provide a more
   * efficient 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.
   * @see        java.io.InputStream#read()
   */
  public int read(byte b[], int off, int len) throws IOException {
    SecureRMISocketFactory.setLocalThreadLastReadSocket(socket);
    return(istream.read(b, off, 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>.
   * This may result from any of a number of conditions; reaching end of file
   * before <code>n</code> bytes have been skipped is only one possibility.
   * The actual number of bytes skipped is returned.  If <code>n</code> is
   * negative, no bytes are skipped.
   *
   * <p> The <code>skip</code> method of <code>InputStream</code> creates a
   * byte array and then repeatedly 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.
   */
  public long skip(long n) throws IOException {
    return(istream.skip(n));
  }

  /**
   * Returns the number of bytes that can be read (or skipped over) from
   * this input stream without blocking by the next caller of a method for
   * this input stream.  The next caller might be the same thread or or
   * another thread.
   *
   * <p> The <code>available</code> method for class <code>InputStream</code>
   * always returns <code>0</code>.
   *
   * <p> This method should 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(istream.available());
  }

  /**
   * Closes this input stream and releases any system resources associated
   * with the stream.
   *
   * <p> The <code>close</code> method of <code>InputStream</code> does
   * nothing.
   *
   * @exception  IOException  if an I/O error occurs.
   */
  public void close() throws IOException {
    istream.close();
  }

  /**
   * Marks the current position in this input stream. A subsequent call to
   * the <code>reset</code> method repositions this stream at the last marked
   * position so that subsequent reads re-read the same bytes.
   *
   * <p> The <code>readlimit</code> arguments tells this input stream to
   * allow that many bytes to be read before the mark position gets
   * invalidated.
   *
   * <p> The general contract of <code>mark</code> is that, if the method
   * <code>markSupported</code> returns <code>true</code>, the stream somehow
   * remembers all the bytes read after the call to <code>mark</code> and
   * stands ready to supply those same bytes again if and whenever the method
   * <code>reset</code> is called.  However, the stream is not required to
   * remember any data at all if more than <code>readlimit</code> bytes are
   * read from the stream before <code>reset</code> is called.
   *
   * <p> The <code>mark</code> method of <code>InputStream</code> does
   * nothing.
   *
   * @param   readlimit   the maximum limit of bytes that can be read before
   *                      the mark position becomes invalid.
   * @see     java.io.InputStream#reset()
   */
  public void mark(int readlimit) {
    istream.mark(readlimit);
  }

  /**
   * Repositions this stream to the position at the time the
   * <code>mark</code> method was last called on this input stream.
   *
   * <p> The general contract of <code>reset</code> is:
   *
   * <p><ul>
   *
   * <li> If the method <code>markSupported</code> returns
   * <code>true</code>, then:
   *
   *     <ul><li> If the method <code>mark</code> has not been called since
   *     the stream was created, or the number of bytes read from the stream
   *     since <code>mark</code> was last called is larger than the argument
   *     to <code>mark</code> at that last call, then an
   *     <code>IOException</code> might be thrown.
   *
   *     <li> If such an <code>IOException</code> is not thrown, then the
   *     stream is reset to a state such that all the bytes read since the
   *     most recent call to <code>mark</code> (or since the start of the
   *     file, if <code>mark</code> has not been called) will be resupplied
   *     to subsequent callers of the <code>read</code> method, followed by
   *     any bytes that otherwise would have been the next input data as of
   *     the time of the call to <code>reset</code>. </ul>
   *
   * <li> If the method <code>markSupported</code> returns
   * <code>false</code>, then:
   *
   *     <ul><li> The call to <code>reset</code> may throw an
   *     <code>IOException</code>.
   *
   *     <li> If an <code>IOException</code> is not thrown, then the stream
   *     is reset to a fixed state that depends on the particular type of the
   *     input stream and how it was created. The bytes that will be supplied
   *     to subsequent callers of the <code>read</code> method depend on the
   *     particular type of the input stream. </ul></ul>
   *
   * <p> The method <code>reset</code> for class <code>InputStream</code>
   * does nothing and always throws an <code>IOException</code>.
   *
   * @exception  IOException  if this stream has not been marked or if the
   *               mark has been invalidated.
   * @see     java.io.InputStream#mark(int)
   * @see     java.io.IOException
   */
  public void reset() throws IOException {
    istream.reset();
  }

  /**
   * Tests if this input stream supports the <code>mark</code> and
   * <code>reset</code> methods. Whether or not <code>mark</code> and
   * <code>reset</code> are supported is an invariant property of a
   * particular input stream instance. The <code>markSupported</code> method
   * of <code>InputStream</code> returns <code>false</code>.
   *
   * @return  <code>true</code> if this stream instance supports the mark
   *          and reset methods; <code>false</code> otherwise.
   * @see     java.io.InputStream#mark(int)
   * @see     java.io.InputStream#reset()
   */
  public boolean markSupported() {
    return(istream.markSupported());
  }
}