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}