1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
|
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package java.io;
import java.util.Arrays;
/**
* Places information on a communications pipe. When two threads want to pass
* data back and forth, one creates a piped writer and the other creates a piped
* reader.
*
* @see PipedReader
*/
public class PipedWriter extends Writer {
private PipedReader destination;
private boolean isClosed;
/**
* Constructs a new unconnected {@code PipedWriter}. The resulting writer
* must be connected to a {@code PipedReader} before data may be written to
* it.
*
* @see PipedReader
*/
public PipedWriter() {
}
/**
* Constructs a new {@code PipedWriter} connected to {@code destination}.
* Any data written to this writer can be read from {@code destination}.
*
* @param destination
* the {@code PipedReader} to connect to.
* @throws IOException
* if {@code destination} is already connected.
*/
public PipedWriter(PipedReader destination) throws IOException {
super(destination);
connect(destination);
}
/**
* Closes this writer. If a {@link PipedReader} is connected to this writer,
* it is closed as well and the pipe is disconnected. Any data buffered in
* the reader can still be read.
*
* @throws IOException
* if an error occurs while closing this writer.
*/
@Override
public void close() throws IOException {
PipedReader reader = destination;
if (reader != null) {
reader.done();
isClosed = true;
destination = null;
}
}
/**
* Connects this {@code PipedWriter} to a {@link PipedReader}. Any data
* written to this writer becomes readable in the reader.
*
* @param reader
* the reader to connect to.
* @throws IOException
* if this writer is closed or already connected, or if {@code
* reader} is already connected.
*/
public void connect(PipedReader reader) throws IOException {
if (reader == null) {
throw new NullPointerException("reader == null");
}
synchronized (reader) {
if (this.destination != null) {
throw new IOException("Pipe already connected");
}
reader.establishConnection();
this.lock = reader;
this.destination = reader;
}
}
/**
* Notifies the readers of this {@code PipedReader} that characters can be read. This
* method does nothing if this Writer is not connected.
*
* @throws IOException
* if an I/O error occurs while flushing this writer.
*/
@Override
public void flush() throws IOException {
PipedReader reader = destination;
if (isClosed) {
throw new IOException("Pipe is closed");
}
if (reader == null) {
return;
}
synchronized (reader) {
reader.notifyAll();
}
}
/**
* Writes {@code count} characters from the character array {@code buffer}
* starting at offset {@code index} to this writer. The written data can
* then be read from the connected {@link PipedReader} instance.
* <p>
* Separate threads should be used to write to a {@code PipedWriter} and to
* read from the connected {@code PipedReader}. If the same thread is used,
* a deadlock may occur.
*
* @param buffer
* the buffer to write.
* @param offset
* the index of the first character in {@code buffer} to write.
* @param count
* the number of characters from {@code buffer} to write to this
* writer.
* @throws IndexOutOfBoundsException
* if {@code offset < 0} or {@code count < 0}, or if {@code
* offset + count} is bigger than the length of {@code buffer}.
* @throws InterruptedIOException
* if the pipe is full and the current thread is interrupted
* waiting for space to write data. This case is not currently
* handled correctly.
* @throws IOException
* if this writer is closed or not connected, if the target
* reader is closed or if the thread reading from the target
* reader is no longer alive. This case is currently not handled
* correctly.
* @throws NullPointerException
* if {@code buffer} is {@code null}.
*/
@Override
public void write(char[] buffer, int offset, int count) throws IOException {
PipedReader reader = destination;
if (reader == null) {
throw new IOException("Pipe not connected");
}
reader.receive(buffer, offset, count);
}
/**
* Writes a single character {@code c} to this writer. This character can
* then be read from the connected {@link PipedReader} instance.
* <p>
* Separate threads should be used to write to a {@code PipedWriter} and to
* read from the connected {@code PipedReader}. If the same thread is used,
* a deadlock may occur.
*
* @param c
* the character to write.
* @throws InterruptedIOException
* if the pipe is full and the current thread is interrupted
* waiting for space to write data. This case is not currently
* handled correctly.
* @throws IOException
* if this writer is closed or not connected, if the target
* reader is closed or if the thread reading from the target
* reader is no longer alive. This case is currently not handled
* correctly.
*/
@Override
public void write(int c) throws IOException {
PipedReader reader = destination;
if (reader == null) {
throw new IOException("Pipe not connected");
}
reader.receive((char) c);
}
}
|
