001/* ObjectInput.java -- Read object data from a stream
002   Copyright (C) 1998,2003 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010 
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package java.io; 
040
041/**
042  * This interface extends the <code>DataInput</code> interface to provide a
043  * facility to read objects as well as primitive types from a stream.  It
044  * also has methods that allow input to be done in a manner similar to
045  * <code>InputStream</code>
046  *
047  * @author Aaron M. Renn (arenn@urbanophile.com)
048  *
049  * @see DataInput
050  */
051public interface ObjectInput extends DataInput
052{
053  /**
054    * This method returns the number of bytes that can be read without
055    * blocking.
056    *
057    * @return The number of bytes available before blocking
058    *
059    * @exception IOException If an error occurs
060    */
061  int available() throws IOException;
062
063  /**
064    * This method reading a byte of data from a stream.  It returns that byte
065    * as an <code>int</code>.  This method blocks if no data is available 
066    * to be read.
067    * 
068    * @return The byte of data read
069    *
070    * @exception IOException If an error occurs
071    */
072  int read() throws IOException;
073
074  /**
075    * This method reads raw bytes and stores them them a byte array buffer.
076    * Note that this method will block if no data is available.  However, 
077    * it will not necessarily block until it fills the entire buffer.  That is,
078    * a "short count" is possible.
079    *
080    * @param buf The byte array to receive the data read
081    *
082    * @return The actual number of bytes read or -1 if end of stream
083    *
084    * @exception IOException If an error occurs
085    */
086  int read(byte[] buf) throws IOException;
087
088  /**
089    * This method reads raw bytes and stores them in a byte array buffer
090    * <code>buf</code> starting at position <code>offset</code> into the 
091    * buffer.  A 
092    * maximum of <code>len</code> bytes will be read.  Note that this method
093    * blocks if no data is available, but will not necessarily block until
094    * it can read <code>len</code> bytes of data.  That is, a "short count" is
095    * possible.
096    *
097    * @param buf The byte array to receive the data read
098    * @param offset The offset into <code>buf</code> to start storing data
099    * @param len The maximum number of bytes to read
100    *
101    * @return The actual number of bytes read or -1 if end of stream
102    *
103    * @exception IOException If an error occurs
104    */
105  int read(byte[] buf, int offset, int len) throws IOException;
106
107  /**
108    * Reads an object instance and returns it.  If the class for the object
109    * being read cannot be found, then a <code>ClassNotFoundException</code>
110    * will be thrown.
111    *
112    * @return The object instance that was read
113    *
114    * @exception ClassNotFoundException If a class for the object cannot be 
115    * found
116    * @exception IOException If any other error occurs
117    */
118  Object readObject() 
119    throws ClassNotFoundException, IOException;
120
121  /**
122    * This method causes the specified number of bytes to be read and
123    * discarded.  It is possible that fewer than the requested number of bytes
124    * will actually be skipped.
125    *
126    * @param numBytes The number of bytes to skip
127    *
128    * @return The actual number of bytes skipped
129    *
130    * @exception IOException If an error occurs
131    */
132  long skip(long numBytes) throws IOException;
133
134  /**
135    * This method closes the input source
136    *
137    * @exception IOException If an error occurs
138    */
139  void close() throws IOException;
140}