1 /*
2 * Copyright (c) 1994, 2015, 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 import java.util.concurrent.atomic.AtomicBoolean;
29
30 /**
31 * This class is the superclass of all classes that filter output
32 * streams. These streams sit on top of an already existing output
33 * stream (the <i>underlying</i> output stream) which it uses as its
34 * basic sink of data, but possibly transforming the data along the
35 * way or providing additional functionality.
36 * <p>
37 * The class <code>FilterOutputStream</code> itself simply overrides
38 * all methods of <code>OutputStream</code> with versions that pass
39 * all requests to the underlying output stream. Subclasses of
40 * <code>FilterOutputStream</code> may further override some of these
41 * methods as well as provide additional methods and fields.
42 *
43 * @author Jonathan Payne
44 * @since 1.0
45 */
46 public class FilterOutputStream extends OutputStream {
47 /**
48 * The underlying output stream to be filtered.
49 */
50 protected OutputStream out;
51
52 /**
53 * Whether the stream is closed; initialized to false.
54 */
55 private final AtomicBoolean closed = new AtomicBoolean();
56
57 /**
58 * Creates an output stream filter built on top of the specified
59 * underlying output stream.
60 *
61 * @param out the underlying output stream to be assigned to
62 * the field <tt>this.out</tt> for later use, or
63 * <code>null</code> if this instance is to be
64 * created without an underlying stream.
65 */
66 public FilterOutputStream(OutputStream out) {
67 this.out = out;
68 }
69
70 /**
71 * Writes the specified <code>byte</code> to this output stream.
72 * <p>
73 * The <code>write</code> method of <code>FilterOutputStream</code>
74 * calls the <code>write</code> method of its underlying output stream,
75 * that is, it performs <tt>out.write(b)</tt>.
76 * <p>
77 * Implements the abstract <tt>write</tt> method of <tt>OutputStream</tt>.
78 *
79 * @param b the <code>byte</code>.
80 * @exception IOException if an I/O error occurs.
81 */
82 @Override
83 public void write(int b) throws IOException {
84 out.write(b);
85 }
86
87 /**
88 * Writes <code>b.length</code> bytes to this output stream.
89 * <p>
90 * The <code>write</code> method of <code>FilterOutputStream</code>
91 * calls its <code>write</code> method of three arguments with the
92 * arguments <code>b</code>, <code>0</code>, and
93 * <code>b.length</code>.
94 * <p>
95 * Note that this method does not call the one-argument
96 * <code>write</code> method of its underlying stream with the single
97 * argument <code>b</code>.
98 *
99 * @param b the data to be written.
100 * @exception IOException if an I/O error occurs.
101 * @see java.io.FilterOutputStream#write(byte[], int, int)
102 */
103 @Override
104 public void write(byte b[]) throws IOException {
105 write(b, 0, b.length);
106 }
107
108 /**
109 * Writes <code>len</code> bytes from the specified
110 * <code>byte</code> array starting at offset <code>off</code> to
111 * this output stream.
112 * <p>
113 * The <code>write</code> method of <code>FilterOutputStream</code>
114 * calls the <code>write</code> method of one argument on each
115 * <code>byte</code> to output.
116 * <p>
117 * Note that this method does not call the <code>write</code> method
118 * of its underlying input stream with the same arguments. Subclasses
119 * of <code>FilterOutputStream</code> should provide a more efficient
120 * implementation of this method.
121 *
122 * @param b the data.
123 * @param off the start offset in the data.
124 * @param len the number of bytes to write.
125 * @exception IOException if an I/O error occurs.
126 * @see java.io.FilterOutputStream#write(int)
127 */
128 @Override
129 public void write(byte b[], int off, int len) throws IOException {
130 if ((off | len | (b.length - (len + off)) | (off + len)) < 0)
131 throw new IndexOutOfBoundsException();
132
133 for (int i = 0 ; i < len ; i++) {
134 write(b[off + i]);
135 }
136 }
137
138 /**
139 * Flushes this output stream and forces any buffered output bytes
140 * to be written out to the stream.
141 * <p>
142 * The <code>flush</code> method of <code>FilterOutputStream</code>
143 * calls the <code>flush</code> method of its underlying output stream.
144 *
145 * @exception IOException if an I/O error occurs.
146 * @see java.io.FilterOutputStream#out
147 */
148 @Override
149 public void flush() throws IOException {
150 out.flush();
151 }
152
153 /**
154 * Closes this output stream and releases any system resources
155 * associated with the stream.
156 * <p>
157 * When not already closed, the {@code close} method of {@code
158 * FilterOutputStream} calls its {@code flush} method, and then
159 * calls the {@code close} method of its underlying output stream.
160 *
161 * @exception IOException if an I/O error occurs.
162 * @see java.io.FilterOutputStream#flush()
163 * @see java.io.FilterOutputStream#out
164 */
165 @SuppressWarnings("try")
166 @Override
167 public void close() throws IOException {
168 if (closed.compareAndSet(false, true)) {
169 IOException flushException = null;
170
171 try {
172 flush();
173 } catch (IOException e) {
174 flushException = e;
175 } finally {
176 try {
177 out.close();
178 } catch (IOException closeException) {
179 if (flushException != null &&
180 flushException != closeException) {
181 closeException.addSuppressed(flushException);
182 }
183 throw closeException;
184 }
185 }
186
187 if (flushException != null) {
188 throw flushException;
189 }
190 }
191 }
192 }