1 /*
2 * Copyright (c) 1994, 2011, 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.nio.channels.FileChannel;
29 import sun.nio.ch.FileChannelImpl;
30
31
32 /**
33 * A file output stream is an output stream for writing data to a
34 * <code>File</code> or to a <code>FileDescriptor</code>. Whether or not
35 * a file is available or may be created depends upon the underlying
36 * platform. Some platforms, in particular, allow a file to be opened
37 * for writing by only one <tt>FileOutputStream</tt> (or other
38 * file-writing object) at a time. In such situations the constructors in
39 * this class will fail if the file involved is already open.
40 *
41 * <p><code>FileOutputStream</code> is meant for writing streams of raw bytes
42 * such as image data. For writing streams of characters, consider using
43 * <code>FileWriter</code>.
44 *
45 * @author Arthur van Hoff
46 * @see java.io.File
47 * @see java.io.FileDescriptor
48 * @see java.io.FileInputStream
49 * @see java.nio.file.Files#newOutputStream
50 * @since JDK1.0
51 */
52 public
53 class FileOutputStream extends OutputStream
54 {
55 /**
56 * The system dependent file descriptor.
57 */
58 private final FileDescriptor fd;
59
60 /**
61 * True if the file is opened for append.
62 */
63 private final boolean append;
64
65 /**
66 * The associated channel, initialized lazily.
67 */
68 private FileChannel channel;
69
70 private final Object closeLock = new Object();
71 private volatile boolean closed = false;
72
73 /**
74 * Creates a file output stream to write to the file with the
75 * specified name. A new <code>FileDescriptor</code> object is
76 * created to represent this file connection.
77 * <p>
78 * First, if there is a security manager, its <code>checkWrite</code>
79 * method is called with <code>name</code> as its argument.
80 * <p>
81 * If the file exists but is a directory rather than a regular file, does
82 * not exist but cannot be created, or cannot be opened for any other
83 * reason then a <code>FileNotFoundException</code> is thrown.
84 *
85 * @param name the system-dependent filename
86 * @exception FileNotFoundException if the file exists but is a directory
87 * rather than a regular file, does not exist but cannot
88 * be created, or cannot be opened for any other reason
89 * @exception SecurityException if a security manager exists and its
90 * <code>checkWrite</code> method denies write access
91 * to the file.
92 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
93 */
94 public FileOutputStream(String name) throws FileNotFoundException {
95 this(name != null ? new File(name) : null, false);
96 }
97
98 /**
99 * Creates a file output stream to write to the file with the specified
100 * name. If the second argument is <code>true</code>, then
101 * bytes will be written to the end of the file rather than the beginning.
102 * A new <code>FileDescriptor</code> object is created to represent this
103 * file connection.
104 * <p>
105 * First, if there is a security manager, its <code>checkWrite</code>
106 * method is called with <code>name</code> as its argument.
107 * <p>
108 * If the file exists but is a directory rather than a regular file, does
109 * not exist but cannot be created, or cannot be opened for any other
110 * reason then a <code>FileNotFoundException</code> is thrown.
111 *
112 * @param name the system-dependent file name
113 * @param append if <code>true</code>, then bytes will be written
114 * to the end of the file rather than the beginning
115 * @exception FileNotFoundException if the file exists but is a directory
116 * rather than a regular file, does not exist but cannot
117 * be created, or cannot be opened for any other reason.
118 * @exception SecurityException if a security manager exists and its
119 * <code>checkWrite</code> method denies write access
120 * to the file.
121 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
122 * @since JDK1.1
123 */
124 public FileOutputStream(String name, boolean append)
125 throws FileNotFoundException
126 {
127 this(name != null ? new File(name) : null, append);
128 }
129
130 /**
131 * Creates a file output stream to write to the file represented by
132 * the specified <code>File</code> object. A new
133 * <code>FileDescriptor</code> object is created to represent this
134 * file connection.
135 * <p>
136 * First, if there is a security manager, its <code>checkWrite</code>
137 * method is called with the path represented by the <code>file</code>
138 * argument as its argument.
139 * <p>
140 * If the file exists but is a directory rather than a regular file, does
141 * not exist but cannot be created, or cannot be opened for any other
142 * reason then a <code>FileNotFoundException</code> is thrown.
143 *
144 * @param file the file to be opened for writing.
145 * @exception FileNotFoundException if the file exists but is a directory
146 * rather than a regular file, does not exist but cannot
147 * be created, or cannot be opened for any other reason
148 * @exception SecurityException if a security manager exists and its
149 * <code>checkWrite</code> method denies write access
150 * to the file.
151 * @see java.io.File#getPath()
152 * @see java.lang.SecurityException
153 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
154 */
155 public FileOutputStream(File file) throws FileNotFoundException {
156 this(file, false);
157 }
158
159 /**
160 * Creates a file output stream to write to the file represented by
161 * the specified <code>File</code> object. If the second argument is
162 * <code>true</code>, then bytes will be written to the end of the file
163 * rather than the beginning. A new <code>FileDescriptor</code> object is
164 * created to represent this file connection.
165 * <p>
166 * First, if there is a security manager, its <code>checkWrite</code>
167 * method is called with the path represented by the <code>file</code>
168 * argument as its argument.
169 * <p>
170 * If the file exists but is a directory rather than a regular file, does
171 * not exist but cannot be created, or cannot be opened for any other
172 * reason then a <code>FileNotFoundException</code> is thrown.
173 *
174 * @param file the file to be opened for writing.
175 * @param append if <code>true</code>, then bytes will be written
176 * to the end of the file rather than the beginning
177 * @exception FileNotFoundException if the file exists but is a directory
178 * rather than a regular file, does not exist but cannot
179 * be created, or cannot be opened for any other reason
180 * @exception SecurityException if a security manager exists and its
181 * <code>checkWrite</code> method denies write access
182 * to the file.
183 * @see java.io.File#getPath()
184 * @see java.lang.SecurityException
185 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
186 * @since 1.4
187 */
188 public FileOutputStream(File file, boolean append)
189 throws FileNotFoundException
190 {
191 String name = (file != null ? file.getPath() : null);
192 SecurityManager security = System.getSecurityManager();
193 if (security != null) {
194 security.checkWrite(name);
195 }
196 if (name == null) {
197 throw new NullPointerException();
198 }
199 this.fd = new FileDescriptor();
200 this.append = append;
201
202 fd.incrementAndGetUseCount();
203 open(name, append);
204 }
205
206 /**
207 * Creates a file output stream to write to the specified file
208 * descriptor, which represents an existing connection to an actual
209 * file in the file system.
210 * <p>
211 * First, if there is a security manager, its <code>checkWrite</code>
212 * method is called with the file descriptor <code>fdObj</code>
213 * argument as its argument.
214 * <p>
215 * If <code>fdObj</code> is null then a <code>NullPointerException</code>
216 * is thrown.
217 * <p>
218 * This constructor does not throw an exception if <code>fdObj</code>
219 * is {@link java.io.FileDescriptor#valid() invalid}.
220 * However, if the methods are invoked on the resulting stream to attempt
221 * I/O on the stream, an <code>IOException</code> is thrown.
222 *
223 * @param fdObj the file descriptor to be opened for writing
224 * @exception SecurityException if a security manager exists and its
225 * <code>checkWrite</code> method denies
226 * write access to the file descriptor
227 * @see java.lang.SecurityManager#checkWrite(java.io.FileDescriptor)
228 */
229 public FileOutputStream(FileDescriptor fdObj) {
230 SecurityManager security = System.getSecurityManager();
231 if (fdObj == null) {
232 throw new NullPointerException();
233 }
234 if (security != null) {
235 security.checkWrite(fdObj);
236 }
237 this.fd = fdObj;
238 this.append = false;
239
240 /*
241 * FileDescriptor is being shared by streams.
242 * Ensure that it's GC'ed only when all the streams/channels are done
243 * using it.
244 */
245 fd.incrementAndGetUseCount();
246 }
247
248 /**
249 * Opens a file, with the specified name, for overwriting or appending.
250 * @param name name of file to be opened
251 * @param append whether the file is to be opened in append mode
252 */
253 private native void open(String name, boolean append)
254 throws FileNotFoundException;
255
256 /**
257 * Writes the specified byte to this file output stream.
258 *
259 * @param b the byte to be written.
260 * @param append {@code true} if the write operation first
261 * advances the position to the end of file
262 */
263 private native void write(int b, boolean append) throws IOException;
264
265 /**
266 * Writes the specified byte to this file output stream. Implements
267 * the <code>write</code> method of <code>OutputStream</code>.
268 *
269 * @param b the byte to be written.
270 * @exception IOException if an I/O error occurs.
271 */
272 public void write(int b) throws IOException {
273 write(b, append);
274 }
275
276 /**
277 * Writes a sub array as a sequence of bytes.
278 * @param b the data to be written
279 * @param off the start offset in the data
280 * @param len the number of bytes that are written
281 * @param append {@code true} to first advance the position to the
282 * end of file
283 * @exception IOException If an I/O error has occurred.
284 */
285 private native void writeBytes(byte b[], int off, int len, boolean append)
286 throws IOException;
287
288 /**
289 * Writes <code>b.length</code> bytes from the specified byte array
290 * to this file output stream.
291 *
292 * @param b the data.
293 * @exception IOException if an I/O error occurs.
294 */
295 public void write(byte b[]) throws IOException {
296 writeBytes(b, 0, b.length, append);
297 }
298
299 /**
300 * Writes <code>len</code> bytes from the specified byte array
301 * starting at offset <code>off</code> to this file output stream.
302 *
303 * @param b the data.
304 * @param off the start offset in the data.
305 * @param len the number of bytes to write.
306 * @exception IOException if an I/O error occurs.
307 */
308 public void write(byte b[], int off, int len) throws IOException {
309 writeBytes(b, off, len, append);
310 }
311
312 /**
313 * Closes this file output stream and releases any system resources
314 * associated with this stream. This file output stream may no longer
315 * be used for writing bytes.
316 *
317 * <p> If this stream has an associated channel then the channel is closed
318 * as well.
319 *
320 * @exception IOException if an I/O error occurs.
321 *
322 * @revised 1.4
323 * @spec JSR-51
324 */
325 public void close() throws IOException {
326 synchronized (closeLock) {
327 if (closed) {
328 return;
329 }
330 closed = true;
331 }
332
333 if (channel != null) {
334 /*
335 * Decrement FD use count associated with the channel
336 * The use count is incremented whenever a new channel
337 * is obtained from this stream.
338 */
339 fd.decrementAndGetUseCount();
340 channel.close();
341 }
342
343 /*
344 * Decrement FD use count associated with this stream
345 */
346 int useCount = fd.decrementAndGetUseCount();
347
348 /*
349 * If FileDescriptor is still in use by another stream, we
350 * will not close it.
351 */
352 if (useCount <= 0) {
353 close0();
354 }
355 }
356
357 /**
358 * Returns the file descriptor associated with this stream.
359 *
360 * @return the <code>FileDescriptor</code> object that represents
361 * the connection to the file in the file system being used
362 * by this <code>FileOutputStream</code> object.
363 *
364 * @exception IOException if an I/O error occurs.
365 * @see java.io.FileDescriptor
366 */
367 public final FileDescriptor getFD() throws IOException {
368 if (fd != null) return fd;
369 throw new IOException();
370 }
371
372 /**
373 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
374 * object associated with this file output stream. </p>
375 *
376 * <p> The initial {@link java.nio.channels.FileChannel#position()
377 * </code>position<code>} of the returned channel will be equal to the
378 * number of bytes written to the file so far unless this stream is in
379 * append mode, in which case it will be equal to the size of the file.
380 * Writing bytes to this stream will increment the channel's position
381 * accordingly. Changing the channel's position, either explicitly or by
382 * writing, will change this stream's file position.
383 *
384 * @return the file channel associated with this file output stream
385 *
386 * @since 1.4
387 * @spec JSR-51
388 */
389 public FileChannel getChannel() {
390 synchronized (this) {
391 if (channel == null) {
392 channel = FileChannelImpl.open(fd, false, true, append, this);
393
394 /*
395 * Increment fd's use count. Invoking the channel's close()
396 * method will result in decrementing the use count set for
397 * the channel.
398 */
399 fd.incrementAndGetUseCount();
400 }
401 return channel;
402 }
403 }
404
405 /**
406 * Cleans up the connection to the file, and ensures that the
407 * <code>close</code> method of this file output stream is
408 * called when there are no more references to this stream.
409 *
410 * @exception IOException if an I/O error occurs.
411 * @see java.io.FileInputStream#close()
412 */
413 protected void finalize() throws IOException {
414 if (fd != null) {
415 if (fd == FileDescriptor.out || fd == FileDescriptor.err) {
416 flush();
417 } else {
418 close();
419 }
420 }
421 }
422
423 private native void close0() throws IOException;
424
425 private static native void initIDs();
426
427 static {
428 initIDs();
429 }
430
431 }