001/* PipedWriter.java -- Write portion of piped character streams. 002 Copyright (C) 1998, 2000, 2001, 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// NOTE: This implementation is very similar to that of PipedOutputStream. 042// If you fix a bug in here, chances are you should make a similar change to 043// the PipedOutputStream code. 044 045/** 046 * This class writes its chars to a <code>PipedReader</code> to 047 * which it is connected. 048 * <p> 049 * It is highly recommended that a <code>PipedWriter</code> and its 050 * connected <code>PipedReader</code> be in different threads. If 051 * they are in the same thread, read and write operations could deadlock 052 * the thread. 053 * 054 * @author Aaron M. Renn (arenn@urbanophile.com) 055 */ 056public class PipedWriter extends Writer 057{ 058 /** Target PipedReader to which this is connected. Null only if this 059 * Writer hasn't been connected yet. */ 060 PipedReader sink; 061 062 /** Set to true if close() has been called on this Writer. */ 063 boolean closed; 064 065 /** Buffer used to implement single-argument write */ 066 char[] read_buf = new char[1]; 067 068 /** 069 * Create an unconnected PipedWriter. It must be connected 070 * to a <code>PipedReader</code> using the <code>connect</code> 071 * method prior to writing any data or an exception will be thrown. 072 */ 073 public PipedWriter() 074 { 075 } 076 077 /** 078 * Create a new <code>PipedWriter</code> instance 079 * to write to the specified <code>PipedReader</code>. This stream 080 * is then ready for writing. 081 * 082 * @param sink The <code>PipedReader</code> to connect this stream to. 083 * 084 * @exception IOException If <code>sink</code> has already been connected 085 * to a different PipedWriter. 086 */ 087 public PipedWriter(PipedReader sink) throws IOException 088 { 089 sink.connect(this); 090 } 091 092 /** 093 * Connects this object to the specified <code>PipedReader</code> 094 * object. This stream will then be ready for writing. 095 * 096 * @param sink The <code>PipedReader</code> to connect this stream to 097 * 098 * @exception IOException If the stream has not been connected or has 099 * been closed. 100 */ 101 public void connect(PipedReader sink) throws IOException 102 { 103 if (this.sink != null || sink.source != null) 104 throw new IOException ("Already connected"); 105 sink.connect(this); 106 } 107 108 /** 109 * Write a single char of date to the stream. Note that this method will 110 * block if the <code>PipedReader</code> to which this object is 111 * connected has a full buffer. 112 * 113 * @param b The char of data to be written, passed as an <code>int</code>. 114 * 115 * @exception IOException If the stream has not been connected or has 116 * been closed. 117 */ 118 public void write(int b) throws IOException 119 { 120 read_buf[0] = (char) (b & 0xffff); 121 sink.receive (read_buf, 0, 1); 122 } 123 124 /** 125 * This method writes <code>len</code> chars of data from the char array 126 * <code>buf</code> starting at index <code>offset</code> in the array 127 * to the stream. Note that this method will block if the 128 * <code>PipedReader</code> to which this object is connected has 129 * a buffer that cannot hold all of the chars to be written. 130 * 131 * @param buffer The array containing chars to write to the stream. 132 * @param offset The index into the array to start writing chars from. 133 * @param len The number of chars to write. 134 * 135 * @exception IOException If the stream has not been connected or has 136 * been closed. 137 */ 138 public void write(char[] buffer, int offset, int len) throws IOException 139 { 140 if (sink == null) 141 throw new IOException ("Not connected"); 142 if (closed) 143 throw new IOException ("Pipe closed"); 144 145 sink.receive(buffer, offset, len); 146 } 147 148 /** 149 * This method does nothing. 150 * 151 * @exception IOException If the stream is closed. 152 * @specnote You'd think that this method would block until the sink 153 * had read all available data. Thats not the case - this method 154 * appears to be a no-op? 155 */ 156 public void flush() throws IOException 157 { 158 if (closed) 159 throw new IOException ("Pipe closed"); 160 } 161 162 /** 163 * This method closes this stream so that no more data can be written 164 * to it. Any further attempts to write to this stream may throw an 165 * exception 166 * 167 * @exception IOException If an error occurs 168 */ 169 public void close() throws IOException 170 { 171 // A close call on an unconnected PipedWriter has no effect. 172 if (sink != null) 173 { 174 closed = true; 175 // Notify any waiting readers that the stream is now closed. 176 synchronized (sink) 177 { 178 sink.notifyAll(); 179 } 180 } 181 } 182}