1 /*
2 * Copyright (c) 1994, 2013, 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 java.util.concurrent.atomic.AtomicBoolean;
30 import jdk.internal.misc.SharedSecrets;
31 import jdk.internal.misc.JavaIOFileDescriptorAccess;
32 import sun.nio.ch.FileChannelImpl;
33
34
35 /**
36 * A file output stream is an output stream for writing data to a
37 * <code>File</code> or to a <code>FileDescriptor</code>. Whether or not
38 * a file is available or may be created depends upon the underlying
39 * platform. Some platforms, in particular, allow a file to be opened
40 * for writing by only one {@code FileOutputStream} (or other
41 * file-writing object) at a time. In such situations the constructors in
42 * this class will fail if the file involved is already open.
43 *
44 * <p><code>FileOutputStream</code> is meant for writing streams of raw bytes
45 * such as image data. For writing streams of characters, consider using
46 * <code>FileWriter</code>.
47 *
48 * @author Arthur van Hoff
49 * @see java.io.File
50 * @see java.io.FileDescriptor
51 * @see java.io.FileInputStream
52 * @see java.nio.file.Files#newOutputStream
53 * @since 1.0
54 */
55 public
56 class FileOutputStream extends OutputStream
57 {
58 /**
59 * Access to FileDescriptor internals.
60 */
61 private static final JavaIOFileDescriptorAccess fdAccess =
62 SharedSecrets.getJavaIOFileDescriptorAccess();
63
64 /**
65 * The system dependent file descriptor.
66 */
67 private final FileDescriptor fd;
68
69 /**
70 * The associated channel, initialized lazily.
71 */
72 private volatile FileChannel channel;
73
74 /**
75 * The path of the referenced file
76 * (null if the stream is created with a file descriptor)
77 */
78 private final String path;
79
80 private final AtomicBoolean closed = new AtomicBoolean(false);
81
82 /**
83 * Creates a file output stream to write to the file with the
84 * specified name. A new <code>FileDescriptor</code> object is
85 * created to represent this file connection.
86 * <p>
87 * First, if there is a security manager, its <code>checkWrite</code>
88 * method is called with <code>name</code> as its argument.
89 * <p>
90 * If the file exists but is a directory rather than a regular file, does
91 * not exist but cannot be created, or cannot be opened for any other
92 * reason then a <code>FileNotFoundException</code> is thrown.
93 *
94 * @param name the system-dependent filename
95 * @exception FileNotFoundException if the file exists but is a directory
96 * rather than a regular file, does not exist but cannot
97 * be created, or cannot be opened for any other reason
98 * @exception SecurityException if a security manager exists and its
99 * <code>checkWrite</code> method denies write access
100 * to the file.
101 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
102 */
103 public FileOutputStream(String name) throws FileNotFoundException {
104 this(name != null ? new File(name) : null, false);
105 }
106
107 /**
108 * Creates a file output stream to write to the file with the specified
109 * name. If the second argument is <code>true</code>, then
110 * bytes will be written to the end of the file rather than the beginning.
111 * A new <code>FileDescriptor</code> object is created to represent this
112 * file connection.
113 * <p>
114 * First, if there is a security manager, its <code>checkWrite</code>
115 * method is called with <code>name</code> as its argument.
116 * <p>
117 * If the file exists but is a directory rather than a regular file, does
118 * not exist but cannot be created, or cannot be opened for any other
119 * reason then a <code>FileNotFoundException</code> is thrown.
120 *
121 * @param name the system-dependent file name
122 * @param append if <code>true</code>, then bytes will be written
123 * to the end of the file rather than the beginning
124 * @exception FileNotFoundException if the file exists but is a directory
125 * rather than a regular file, does not exist but cannot
126 * be created, or cannot be opened for any other reason.
127 * @exception SecurityException if a security manager exists and its
128 * <code>checkWrite</code> method denies write access
129 * to the file.
130 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
131 * @since 1.1
132 */
133 public FileOutputStream(String name, boolean append)
134 throws FileNotFoundException
135 {
136 this(name != null ? new File(name) : null, append);
137 }
138
139 /**
140 * Creates a file output stream to write to the file represented by
141 * the specified <code>File</code> object. A new
142 * <code>FileDescriptor</code> object is created to represent this
143 * file connection.
144 * <p>
145 * First, if there is a security manager, its <code>checkWrite</code>
146 * method is called with the path represented by the <code>file</code>
147 * argument as its argument.
148 * <p>
149 * If the file exists but is a directory rather than a regular file, does
150 * not exist but cannot be created, or cannot be opened for any other
151 * reason then a <code>FileNotFoundException</code> is thrown.
152 *
153 * @param file the file to be opened for writing.
154 * @exception FileNotFoundException if the file exists but is a directory
155 * rather than a regular file, does not exist but cannot
156 * be created, or cannot be opened for any other reason
157 * @exception SecurityException if a security manager exists and its
158 * <code>checkWrite</code> method denies write access
159 * to the file.
160 * @see java.io.File#getPath()
161 * @see java.lang.SecurityException
162 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
163 */
164 public FileOutputStream(File file) throws FileNotFoundException {
165 this(file, false);
166 }
167
168 /**
169 * Creates a file output stream to write to the file represented by
170 * the specified <code>File</code> object. If the second argument is
171 * <code>true</code>, then bytes will be written to the end of the file
172 * rather than the beginning. A new <code>FileDescriptor</code> object is
173 * created to represent this file connection.
174 * <p>
175 * First, if there is a security manager, its <code>checkWrite</code>
176 * method is called with the path represented by the <code>file</code>
177 * argument as its argument.
178 * <p>
179 * If the file exists but is a directory rather than a regular file, does
180 * not exist but cannot be created, or cannot be opened for any other
181 * reason then a <code>FileNotFoundException</code> is thrown.
182 *
183 * @param file the file to be opened for writing.
184 * @param append if <code>true</code>, then bytes will be written
185 * to the end of the file rather than the beginning
186 * @exception FileNotFoundException if the file exists but is a directory
187 * rather than a regular file, does not exist but cannot
188 * be created, or cannot be opened for any other reason
189 * @exception SecurityException if a security manager exists and its
190 * <code>checkWrite</code> method denies write access
191 * to the file.
192 * @see java.io.File#getPath()
193 * @see java.lang.SecurityException
194 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
195 * @since 1.4
196 */
197 public FileOutputStream(File file, boolean append)
198 throws FileNotFoundException
199 {
200 String name = (file != null ? file.getPath() : null);
201 SecurityManager security = System.getSecurityManager();
202 if (security != null) {
203 security.checkWrite(name);
204 }
205 if (name == null) {
206 throw new NullPointerException();
207 }
208 if (file.isInvalid()) {
209 throw new FileNotFoundException("Invalid file path");
210 }
211 this.fd = new FileDescriptor();
212 fd.attach(this);
213 this.path = name;
214
215 open(name, append);
216 }
217
218 /**
219 * Creates a file output stream to write to the specified file
220 * descriptor, which represents an existing connection to an actual
221 * file in the file system.
222 * <p>
223 * First, if there is a security manager, its <code>checkWrite</code>
224 * method is called with the file descriptor <code>fdObj</code>
225 * argument as its argument.
226 * <p>
227 * If <code>fdObj</code> is null then a <code>NullPointerException</code>
228 * is thrown.
229 * <p>
230 * This constructor does not throw an exception if <code>fdObj</code>
231 * is {@link java.io.FileDescriptor#valid() invalid}.
232 * However, if the methods are invoked on the resulting stream to attempt
233 * I/O on the stream, an <code>IOException</code> is thrown.
234 *
235 * @param fdObj the file descriptor to be opened for writing
236 * @exception SecurityException if a security manager exists and its
237 * <code>checkWrite</code> method denies
238 * write access to the file descriptor
239 * @see java.lang.SecurityManager#checkWrite(java.io.FileDescriptor)
240 */
241 public FileOutputStream(FileDescriptor fdObj) {
242 SecurityManager security = System.getSecurityManager();
243 if (fdObj == null) {
244 throw new NullPointerException();
245 }
246 if (security != null) {
247 security.checkWrite(fdObj);
248 }
249 this.fd = fdObj;
250 this.path = null;
251
252 fd.attach(this);
253 }
254
255 /**
256 * Opens a file, with the specified name, for overwriting or appending.
257 * @param name name of file to be opened
258 * @param append whether the file is to be opened in append mode
259 */
260 private native void open0(String name, boolean append)
261 throws FileNotFoundException;
262
263 // wrap native call to allow instrumentation
264 /**
265 * Opens a file, with the specified name, for overwriting or appending.
266 * @param name name of file to be opened
267 * @param append whether the file is to be opened in append mode
268 */
269 private void open(String name, boolean append)
270 throws FileNotFoundException {
271 open0(name, append);
272 }
273
274 /**
275 * Writes the specified byte to this file output stream.
276 *
277 * @param b the byte to be written.
278 * @param append {@code true} if the write operation first
279 * advances the position to the end of file
280 */
281 private native void write(int b, boolean append) throws IOException;
282
283 /**
284 * Writes the specified byte to this file output stream. Implements
285 * the <code>write</code> method of <code>OutputStream</code>.
286 *
287 * @param b the byte to be written.
288 * @exception IOException if an I/O error occurs.
289 */
290 public void write(int b) throws IOException {
291 write(b, fdAccess.getAppend(fd));
292 }
293
294 /**
295 * Writes a sub array as a sequence of bytes.
296 * @param b the data to be written
297 * @param off the start offset in the data
298 * @param len the number of bytes that are written
299 * @param append {@code true} to first advance the position to the
300 * end of file
301 * @exception IOException If an I/O error has occurred.
302 */
303 private native void writeBytes(byte b[], int off, int len, boolean append)
304 throws IOException;
305
306 /**
307 * Writes <code>b.length</code> bytes from the specified byte array
308 * to this file output stream.
309 *
310 * @param b the data.
311 * @exception IOException if an I/O error occurs.
312 */
313 public void write(byte b[]) throws IOException {
314 writeBytes(b, 0, b.length, fdAccess.getAppend(fd));
315 }
316
317 /**
318 * Writes <code>len</code> bytes from the specified byte array
319 * starting at offset <code>off</code> to this file output stream.
320 *
321 * @param b the data.
322 * @param off the start offset in the data.
323 * @param len the number of bytes to write.
324 * @exception IOException if an I/O error occurs.
325 */
326 public void write(byte b[], int off, int len) throws IOException {
327 writeBytes(b, off, len, fdAccess.getAppend(fd));
328 }
329
330 /**
331 * Closes this file output stream and releases any system resources
332 * associated with this stream. This file output stream may no longer
333 * be used for writing bytes.
334 *
335 * <p> If this stream has an associated channel then the channel is closed
336 * as well.
337 *
338 * @exception IOException if an I/O error occurs.
339 *
340 * @revised 1.4
341 * @spec JSR-51
342 */
343 public void close() throws IOException {
344 if (!closed.compareAndSet(false, true)) {
345 // if compareAndSet() returns false closed was already true
346 return;
347 }
348
349 FileChannel fc = channel;
350 if (fc != null) {
351 fc.close();
352 }
353
354 fd.closeAll(new Closeable() {
355 public void close() throws IOException {
356 close0();
357 }
358 });
359 }
360
361 /**
362 * Returns the file descriptor associated with this stream.
363 *
364 * @return the <code>FileDescriptor</code> object that represents
365 * the connection to the file in the file system being used
366 * by this <code>FileOutputStream</code> object.
367 *
368 * @exception IOException if an I/O error occurs.
369 * @see java.io.FileDescriptor
370 */
371 public final FileDescriptor getFD() throws IOException {
372 if (fd != null) {
373 return fd;
374 }
375 throw new IOException();
376 }
377
378 /**
379 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
380 * object associated with this file output stream.
381 *
382 * <p> The initial {@link java.nio.channels.FileChannel#position()
383 * position} of the returned channel will be equal to the
384 * number of bytes written to the file so far unless this stream is in
385 * append mode, in which case it will be equal to the size of the file.
386 * Writing bytes to this stream will increment the channel's position
387 * accordingly. Changing the channel's position, either explicitly or by
388 * writing, will change this stream's file position.
389 *
390 * @return the file channel associated with this file output stream
391 *
392 * @since 1.4
393 * @spec JSR-51
394 */
395 public FileChannel getChannel() {
396 FileChannel fc = this.channel;
397 if (fc == null) {
398 synchronized (this) {
399 fc = this.channel;
400 if (fc == null) {
401 this.channel = fc = FileChannelImpl.open(fd, path, false, true, this);
402 if (closed.get()) {
403 try {
404 fc.close();
405 } catch (IOException ioe) {
406 throw new InternalError(ioe); // should not happen
407 }
408 }
409 }
410 }
411 }
412 return fc;
413 }
414
415 /**
416 * Cleans up the connection to the file, and ensures that the
417 * <code>close</code> method of this file output stream is
418 * called when there are no more references to this stream.
419 *
420 * @exception IOException if an I/O error occurs.
421 * @see java.io.FileInputStream#close()
422 */
423 protected void finalize() throws IOException {
424 if (fd != null) {
425 if (fd == FileDescriptor.out || fd == FileDescriptor.err) {
426 flush();
427 } else {
428 /* if fd is shared, the references in FileDescriptor
429 * will ensure that finalizer is only called when
430 * safe to do so. All references using the fd have
431 * become unreachable. We can call close()
432 */
433 close();
434 }
435 }
436 }
437
438 private native void close0() throws IOException;
439
440 private static native void initIDs();
441
442 static {
443 initIDs();
444 }
445
446 }