1 /*
2 * Copyright (c) 1994, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.io;
27
28 /**
29 * This class is the superclass of all classes that filter output
30 * streams. These streams sit on top of an already existing output
31 * stream (the <i>underlying</i> output stream) which it uses as its
32 * basic sink of data, but possibly transforming the data along the
33 * way or providing additional functionality.
34 * <p>
35 * The class <code>FilterOutputStream</code> itself simply overrides
36 * all methods of <code>OutputStream</code> with versions that pass
37 * all requests to the underlying output stream. Subclasses of
38 * <code>FilterOutputStream</code> may further override some of these
39 * methods as well as provide additional methods and fields.
40 *
41 * @author Jonathan Payne
42 * @since 1.0
43 */
44 public class FilterOutputStream extends OutputStream {
45 /**
46 * The underlying output stream to be filtered.
47 */
48 protected OutputStream out;
49
50 /**
51 * Whether the stream is closed; implicitly initialized to false.
52 */
53 private volatile boolean closed;
54
55 /**
56 * Object used to prevent a race on the 'closed' instance variable.
57 */
58 private final Object closeLock = new Object();
59
60 /**
61 * Creates an output stream filter built on top of the specified
62 * underlying output stream.
63 *
64 * @param out the underlying output stream to be assigned to
65 * the field {@code this.out} for later use, or
66 * <code>null</code> if this instance is to be
67 * created without an underlying stream.
68 */
69 public FilterOutputStream(OutputStream out) {
70 this.out = out;
71 }
72
73 /**
74 * Writes the specified <code>byte</code> to this output stream.
75 * <p>
76 * The <code>write</code> method of <code>FilterOutputStream</code>
77 * calls the <code>write</code> method of its underlying output stream,
78 * that is, it performs {@code out.write(b)}.
79 * <p>
80 * Implements the abstract {@code write} method of {@code OutputStream}.
81 *
82 * @param b the <code>byte</code>.
83 * @exception IOException if an I/O error occurs.
84 */
85 @Override
86 public void write(int b) throws IOException {
87 out.write(b);
88 }
89
90 /**
91 * Writes <code>b.length</code> bytes to this output stream.
92 * <p>
93 * The <code>write</code> method of <code>FilterOutputStream</code>
94 * calls its <code>write</code> method of three arguments with the
95 * arguments <code>b</code>, <code>0</code>, and
96 * <code>b.length</code>.
97 * <p>
98 * Note that this method does not call the one-argument
99 * <code>write</code> method of its underlying output stream with
100 * the single argument <code>b</code>.
101 *
102 * @param b the data to be written.
103 * @exception IOException if an I/O error occurs.
104 * @see java.io.FilterOutputStream#write(byte[], int, int)
105 */
106 @Override
107 public void write(byte b[]) throws IOException {
108 write(b, 0, b.length);
109 }
110
111 /**
112 * Writes <code>len</code> bytes from the specified
113 * <code>byte</code> array starting at offset <code>off</code> to
114 * this output stream.
115 * <p>
116 * The <code>write</code> method of <code>FilterOutputStream</code>
117 * calls the <code>write</code> method of one argument on each
118 * <code>byte</code> to output.
119 * <p>
120 * Note that this method does not call the <code>write</code> method
121 * of its underlying output stream with the same arguments. Subclasses
122 * of <code>FilterOutputStream</code> should provide a more efficient
123 * implementation of this method.
124 *
125 * @param b the data.
126 * @param off the start offset in the data.
127 * @param len the number of bytes to write.
128 * @exception IOException if an I/O error occurs.
129 * @see java.io.FilterOutputStream#write(int)
130 */
131 @Override
132 public void write(byte b[], int off, int len) throws IOException {
133 if ((off | len | (b.length - (len + off)) | (off + len)) < 0)
134 throw new IndexOutOfBoundsException();
135
136 for (int i = 0 ; i < len ; i++) {
137 write(b[off + i]);
138 }
139 }
140
141 /**
142 * Flushes this output stream and forces any buffered output bytes
143 * to be written out to the stream.
144 * <p>
145 * The <code>flush</code> method of <code>FilterOutputStream</code>
146 * calls the <code>flush</code> method of its underlying output stream.
147 *
148 * @exception IOException if an I/O error occurs.
149 * @see java.io.FilterOutputStream#out
150 */
151 @Override
152 public void flush() throws IOException {
153 out.flush();
154 }
155
156 /**
157 * Closes this output stream and releases any system resources
158 * associated with the stream.
159 * <p>
160 * When not already closed, the {@code close} method of {@code
161 * FilterOutputStream} calls its {@code flush} method, and then
162 * calls the {@code close} method of its underlying output stream.
163 *
164 * @exception IOException if an I/O error occurs.
165 * @see java.io.FilterOutputStream#flush()
166 * @see java.io.FilterOutputStream#out
167 */
168 @Override
169 public void close() throws IOException {
170 if (closed) {
171 return;
172 }
173 synchronized (closeLock) {
174 if (closed) {
175 return;
176 }
177 closed = true;
178 }
179
180 Throwable flushException = null;
181 try {
182 flush();
183 } catch (Throwable e) {
184 flushException = e;
185 throw e;
186 } finally {
187 if (flushException == null) {
188 out.close();
189 } else {
190 try {
191 out.close();
192 } catch (Throwable closeException) {
193 // evaluate possible precedence of flushException over closeException
194 if ((flushException instanceof ThreadDeath) &&
195 !(closeException instanceof ThreadDeath)) {
196 flushException.addSuppressed(closeException);
197 throw (ThreadDeath) flushException;
198 }
199
200 if (flushException != closeException) {
201 closeException.addSuppressed(flushException);
202 }
203
204 throw closeException;
205 }
206 }
207 }
208 }
209 }