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 /**
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 boolean closed;
54
55 /**
56 * Creates an output stream filter built on top of the specified
57 * underlying output stream.
58 *
59 * @param out the underlying output stream to be assigned to
60 * the field <tt>this.out</tt> for later use, or
61 * <code>null</code> if this instance is to be
62 * created without an underlying stream.
63 */
64 public FilterOutputStream(OutputStream out) {
65 this.out = out;
66 }
67
68 /**
69 * Writes the specified <code>byte</code> to this output stream.
70 * <p>
71 * The <code>write</code> method of <code>FilterOutputStream</code>
72 * calls the <code>write</code> method of its underlying output stream,
73 * that is, it performs <tt>out.write(b)</tt>.
74 * <p>
75 * Implements the abstract <tt>write</tt> method of <tt>OutputStream</tt>.
76 *
77 * @param b the <code>byte</code>.
78 * @exception IOException if an I/O error occurs.
79 */
80 @Override
81 public void write(int b) throws IOException {
82 out.write(b);
83 }
84
85 /**
86 * Writes <code>b.length</code> bytes to this output stream.
87 * <p>
88 * The <code>write</code> method of <code>FilterOutputStream</code>
89 * calls its <code>write</code> method of three arguments with the
90 * arguments <code>b</code>, <code>0</code>, and
91 * <code>b.length</code>.
92 * <p>
93 * Note that this method does not call the one-argument
94 * <code>write</code> method of its underlying stream with the single
95 * argument <code>b</code>.
96 *
97 * @param b the data to be written.
98 * @exception IOException if an I/O error occurs.
99 * @see java.io.FilterOutputStream#write(byte[], int, int)
100 */
101 @Override
102 public void write(byte b[]) throws IOException {
103 write(b, 0, b.length);
104 }
105
106 /**
107 * Writes <code>len</code> bytes from the specified
108 * <code>byte</code> array starting at offset <code>off</code> to
109 * this output stream.
110 * <p>
111 * The <code>write</code> method of <code>FilterOutputStream</code>
112 * calls the <code>write</code> method of one argument on each
113 * <code>byte</code> to output.
114 * <p>
115 * Note that this method does not call the <code>write</code> method
116 * of its underlying input stream with the same arguments. Subclasses
117 * of <code>FilterOutputStream</code> should provide a more efficient
118 * implementation of this method.
119 *
120 * @param b the data.
121 * @param off the start offset in the data.
122 * @param len the number of bytes to write.
123 * @exception IOException if an I/O error occurs.
124 * @see java.io.FilterOutputStream#write(int)
125 */
126 @Override
127 public void write(byte b[], int off, int len) throws IOException {
128 if ((off | len | (b.length - (len + off)) | (off + len)) < 0)
129 throw new IndexOutOfBoundsException();
130
131 for (int i = 0 ; i < len ; i++) {
132 write(b[off + i]);
133 }
134 }
135
136 /**
137 * Flushes this output stream and forces any buffered output bytes
138 * to be written out to the stream.
139 * <p>
140 * The <code>flush</code> method of <code>FilterOutputStream</code>
141 * calls the <code>flush</code> method of its underlying output stream.
142 *
143 * @exception IOException if an I/O error occurs.
144 * @see java.io.FilterOutputStream#out
145 */
146 @Override
147 public void flush() throws IOException {
148 out.flush();
149 }
150
151 /**
152 * Closes this output stream and releases any system resources
153 * associated with the stream.
154 * <p>
155 * When not already closed, the {@code close} method of {@code
156 * FilterOutputStream} calls its {@code flush} method, and then
157 * calls the {@code close} method of its underlying output stream.
158 *
159 * @exception IOException if an I/O error occurs.
160 * @see java.io.FilterOutputStream#flush()
161 * @see java.io.FilterOutputStream#out
162 */
163 @Override
164 public void close() throws IOException {
165 if (closed) {
166 return;
167 }
168 closed = true;
169
170 Throwable flushException = null;
171 try {
172 flush();
173 } catch (Throwable e) {
174 flushException = e;
175 throw e;
176 } finally {
177 if (flushException == null) {
178 out.close();
179 } else {
180 try {
181 out.close();
182 } catch (Throwable closeException) {
183 // evaluate possible precedence of flushException over closeException
184 if ((flushException instanceof ThreadDeath) &&
185 !(closeException instanceof ThreadDeath)) {
186 flushException.addSuppressed(closeException);
187 throw (ThreadDeath) flushException;
188 }
189
190 if (flushException != closeException) {
191 closeException.addSuppressed(flushException);
192 }
193
194 throw closeException;
195 }
196 }
197 }
198 }
199 }