gcc/libjava/java/io/ObjectInput.java

/* ObjectInput.java -- Read object data from a stream
   Copyright (C) 1998,2003 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
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General Public License for more details.

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02111-1307 USA.

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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


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>
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  *
  * @see DataInput
  */
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 <code>int</code>.  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 of 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</code> to start storing data
    * @param len The maximum number of bytes to read
    *
    * @return The actual number of 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 <code>ClassNotFoundException</code>
    * will be thrown.
    *
    * @return The object instance that was read
    *
    * @exception ClassNotFoundException If a class for the object cannot be 
    * found
    * @exception IOException If any other 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 numBytes The number of bytes to skip
    *
    * @return The actual number of bytes skipped
    *
    * @exception IOException If an error occurs
    */
  public abstract long skip(long numBytes) throws IOException;

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

} // interface ObjectInput