/* ObjectInput.java -- Read object data from a stream
   Copyright (C) 1998 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


package java.io; 

/**
  * This interface extends the <code>DataInput</code> interface to provide a
  * facility to read objects as well as primitive types from a stream.  It
  * also has methods that allow input to be done in a manner similar to
  * <code>InputStream</code>
  *
  * @version 0.0
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  */
public interface ObjectInput extends DataInput
{

/**
  * This method returns the number of bytes that can be read without
  * blocking.
  *
  * @return The number of bytes available before blocking
  *
  * @exception IOException If an error occurs
  */
public abstract int
available() throws IOException;

/*************************************************************************/

/**
  * This method reading a byte of data from a stream.  It returns that byte
  * as an int.  This method blocks if no data is available to be read.
  * 
  * @return The byte of data read
  *
  * @exception IOException If an error occurs
  */
public abstract int
read() throws IOException;

/*************************************************************************/

/**
  * This method reads raw bytes and stores them them a byte array buffer.
  * Note that this method will block if no data is available.  However, 
  * it will not necessarily block until it fills the entire buffer.  That is,
  * a "short count" is possible.
  *
  * @param buf The byte array to receive the data read
  *
  * @return The actual number fo bytes read or -1 if end of stream
  *
  * @exception IOException If an error occurs
  */
public abstract int
read(byte[] buf) throws IOException;

/*************************************************************************/

/**
  * This method reads raw bytes and stores them in a byte array buffer
  * <code>buf</code> starting at position <code>offset</code> into the buffer.  A 
  * maximum of <code>len</code> bytes will be read.  Note that this method
  * blocks if no data is available, but will not necessarily block until
  * it can read <code>len</code> bytes of data.  That is, a "short count" is
  * possible.
  *
  * @param buf The byte array to receive the data read
  * @param offset The offset into @code{buf} to start storing data
  * @param len The maximum number of bytes to read
  *
  * @return The actual number fo bytes read or -1 if end of stream
  *
  * @exception IOException If an error occurs
  */
public abstract int
read(byte[] buf, int offset, int len) throws IOException;

/*************************************************************************/

/**
  * Reads an object instance and returns it.  If the class for the object
  * being read cannot be found, then a ClassNotFoundException will
  * be thrown.
  *
  * @return The object instance that was read
  *
  * @exception ClassNotFoundException If a class for the object cannot be found
  * @exception IOException If an error occurs
  */
public abstract Object
readObject() throws ClassNotFoundException, IOException;

/*************************************************************************/

/**
  * This method causes the specified number of bytes to be read and
  * discarded.  It is possible that fewer than the requested number of bytes
  * will actually be skipped.
  *
  * @param num_bytes The number of bytes to skip
  *
  * @return The actual number of bytes skipped
  *
  * @exception IOException If an error occurs
  */
public abstract long
skip(long num_bytes) throws IOException;

/*************************************************************************/

/**
  * This method closes the input source
  *
  * @exception IOException If an error occurs
  */
public abstract void
close() throws IOException;

} // interface ObjectInput