1 /*
2 * Copyright (c) 1994, 2012, 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 import sun.misc.IoTrace;
31
32
33 /**
34 * A file output stream is an output stream for writing data to a
35 * <code>File</code> or to a <code>FileDescriptor</code>. Whether or not
36 * a file is available or may be created depends upon the underlying
37 * platform. Some platforms, in particular, allow a file to be opened
38 * for writing by only one <tt>FileOutputStream</tt> (or other
39 * file-writing object) at a time. In such situations the constructors in
40 * this class will fail if the file involved is already open.
41 *
42 * <p><code>FileOutputStream</code> is meant for writing streams of raw bytes
43 * such as image data. For writing streams of characters, consider using
44 * <code>FileWriter</code>.
45 *
46 * @author Arthur van Hoff
47 * @see java.io.File
48 * @see java.io.FileDescriptor
49 * @see java.io.FileInputStream
50 * @see java.nio.file.Files#newOutputStream
51 * @since JDK1.0
52 */
53 public
54 class FileOutputStream extends OutputStream
55 {
56 /**
57 * The system dependent file descriptor.
58 */
59 private final FileDescriptor fd;
60
61 /**
62 * The path of the referenced file (null if the stream is created with a file descriptor)
63 */
64 private final String path;
65
66 /**
67 * True if the file is opened for append.
68 */
69 private final boolean append;
70
71 /**
72 * The associated channel, initalized lazily.
73 */
74 private FileChannel channel;
75
76 private final Object closeLock = new Object();
77 private volatile boolean closed = false;
78 private static final ThreadLocal<Boolean> runningFinalize =
79 new ThreadLocal<>();
80
81 private static boolean isRunningFinalize() {
82 Boolean val;
83 if ((val = runningFinalize.get()) != null)
84 return val.booleanValue();
85 return false;
86 }
87
88 /**
89 * Creates a file output stream to write to the file with the
90 * specified name. A new <code>FileDescriptor</code> object is
91 * created to represent this file connection.
92 * <p>
93 * First, if there is a security manager, its <code>checkWrite</code>
94 * method is called with <code>name</code> as its argument.
95 * <p>
96 * If the file exists but is a directory rather than a regular file, does
97 * not exist but cannot be created, or cannot be opened for any other
98 * reason then a <code>FileNotFoundException</code> is thrown.
99 *
100 * @param name the system-dependent filename
101 * @exception FileNotFoundException if the file exists but is a directory
102 * rather than a regular file, does not exist but cannot
103 * be created, or cannot be opened for any other reason
104 * @exception SecurityException if a security manager exists and its
105 * <code>checkWrite</code> method denies write access
106 * to the file.
107 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
108 */
109 public FileOutputStream(String name) throws FileNotFoundException {
110 this(name != null ? new File(name) : null, false);
111 }
112
113 /**
114 * Creates a file output stream to write to the file with the specified
115 * name. If the second argument is <code>true</code>, then
116 * bytes will be written to the end of the file rather than the beginning.
117 * A new <code>FileDescriptor</code> object is created to represent this
118 * file connection.
119 * <p>
120 * First, if there is a security manager, its <code>checkWrite</code>
121 * method is called with <code>name</code> as its argument.
122 * <p>
123 * If the file exists but is a directory rather than a regular file, does
124 * not exist but cannot be created, or cannot be opened for any other
125 * reason then a <code>FileNotFoundException</code> is thrown.
126 *
127 * @param name the system-dependent file name
128 * @param append if <code>true</code>, then bytes will be written
129 * to the end of the file rather than the beginning
130 * @exception FileNotFoundException if the file exists but is a directory
131 * rather than a regular file, does not exist but cannot
132 * be created, or cannot be opened for any other reason.
133 * @exception SecurityException if a security manager exists and its
134 * <code>checkWrite</code> method denies write access
135 * to the file.
136 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
137 * @since JDK1.1
138 */
139 public FileOutputStream(String name, boolean append)
140 throws FileNotFoundException
141 {
142 this(name != null ? new File(name) : null, append);
143 }
144
145 /**
146 * Creates a file output stream to write to the file represented by
147 * the specified <code>File</code> object. A new
148 * <code>FileDescriptor</code> object is created to represent this
149 * file connection.
150 * <p>
151 * First, if there is a security manager, its <code>checkWrite</code>
152 * method is called with the path represented by the <code>file</code>
153 * argument as its argument.
154 * <p>
155 * If the file exists but is a directory rather than a regular file, does
156 * not exist but cannot be created, or cannot be opened for any other
157 * reason then a <code>FileNotFoundException</code> is thrown.
158 *
159 * @param file the file to be opened for writing.
160 * @exception FileNotFoundException if the file exists but is a directory
161 * rather than a regular file, does not exist but cannot
162 * be created, or cannot be opened for any other reason
163 * @exception SecurityException if a security manager exists and its
164 * <code>checkWrite</code> method denies write access
165 * to the file.
166 * @see java.io.File#getPath()
167 * @see java.lang.SecurityException
168 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
169 */
170 public FileOutputStream(File file) throws FileNotFoundException {
171 this(file, false);
172 }
173
174 /**
175 * Creates a file output stream to write to the file represented by
176 * the specified <code>File</code> object. If the second argument is
177 * <code>true</code>, then bytes will be written to the end of the file
178 * rather than the beginning. A new <code>FileDescriptor</code> object is
179 * created to represent this file connection.
180 * <p>
181 * First, if there is a security manager, its <code>checkWrite</code>
182 * method is called with the path represented by the <code>file</code>
183 * argument as its argument.
184 * <p>
185 * If the file exists but is a directory rather than a regular file, does
186 * not exist but cannot be created, or cannot be opened for any other
187 * reason then a <code>FileNotFoundException</code> is thrown.
188 *
189 * @param file the file to be opened for writing.
190 * @param append if <code>true</code>, then bytes will be written
191 * to the end of the file rather than the beginning
192 * @exception FileNotFoundException if the file exists but is a directory
193 * rather than a regular file, does not exist but cannot
194 * be created, or cannot be opened for any other reason
195 * @exception SecurityException if a security manager exists and its
196 * <code>checkWrite</code> method denies write access
197 * to the file.
198 * @see java.io.File#getPath()
199 * @see java.lang.SecurityException
200 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
201 * @since 1.4
202 */
203 public FileOutputStream(File file, boolean append)
204 throws FileNotFoundException
205 {
206 String name = (file != null ? file.getPath() : null);
207 SecurityManager security = System.getSecurityManager();
208 if (security != null) {
209 security.checkWrite(name);
210 }
211 if (name == null) {
212 throw new NullPointerException();
213 }
214 this.fd = new FileDescriptor();
215 this.append = append;
216 this.path = name;
217 fd.incrementAndGetUseCount();
218 open(name, append);
219 }
220
221 /**
222 * Creates a file output stream to write to the specified file
223 * descriptor, which represents an existing connection to an actual
224 * file in the file system.
225 * <p>
226 * First, if there is a security manager, its <code>checkWrite</code>
227 * method is called with the file descriptor <code>fdObj</code>
228 * argument as its argument.
229 * <p>
230 * If <code>fdObj</code> is null then a <code>NullPointerException</code>
231 * is thrown.
232 * <p>
233 * This constructor does not throw an exception if <code>fdObj</code>
234 * is {@link java.io.FileDescriptor#valid() invalid}.
235 * However, if the methods are invoked on the resulting stream to attempt
236 * I/O on the stream, an <code>IOException</code> is thrown.
237 *
238 * @param fdObj the file descriptor to be opened for writing
239 * @exception SecurityException if a security manager exists and its
240 * <code>checkWrite</code> method denies
241 * write access to the file descriptor
242 * @see java.lang.SecurityManager#checkWrite(java.io.FileDescriptor)
243 */
244 public FileOutputStream(FileDescriptor fdObj) {
245 SecurityManager security = System.getSecurityManager();
246 if (fdObj == null) {
247 throw new NullPointerException();
248 }
249 if (security != null) {
250 security.checkWrite(fdObj);
251 }
252 this.fd = fdObj;
253 this.path = null;
254 this.append = false;
255
256 /*
257 * FileDescriptor is being shared by streams.
258 * Ensure that it's GC'ed only when all the streams/channels are done
259 * using it.
260 */
261 fd.incrementAndGetUseCount();
262 }
263
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 native void open(String name, boolean append)
270 throws FileNotFoundException;
271
272 /**
273 * Writes the specified byte to this file output stream.
274 *
275 * @param b the byte to be written.
276 * @param append {@code true} if the write operation first
277 * advances the position to the end of file
278 */
279 private native void write(int b, boolean append) throws IOException;
280
281 /**
282 * Writes the specified byte to this file output stream. Implements
283 * the <code>write</code> method of <code>OutputStream</code>.
284 *
285 * @param b the byte to be written.
286 * @exception IOException if an I/O error occurs.
287 */
288 public void write(int b) throws IOException {
289 Object traceContext = IoTrace.fileWriteBegin(path);
290 int bytesWritten = 0;
291 try {
292 write(b, append);
293 bytesWritten = 1;
294 } finally {
295 IoTrace.fileWriteEnd(traceContext, bytesWritten);
296 }
297 }
298
299 /**
300 * Writes a sub array as a sequence of bytes.
301 * @param b the data to be written
302 * @param off the start offset in the data
303 * @param len the number of bytes that are written
304 * @param append {@code true} to first advance the position to the
305 * end of file
306 * @exception IOException If an I/O error has occurred.
307 */
308 private native void writeBytes(byte b[], int off, int len, boolean append)
309 throws IOException;
310
311 /**
312 * Writes <code>b.length</code> bytes from the specified byte array
313 * to this file output stream.
314 *
315 * @param b the data.
316 * @exception IOException if an I/O error occurs.
317 */
318 public void write(byte b[]) throws IOException {
319 Object traceContext = IoTrace.fileWriteBegin(path);
320 int bytesWritten = 0;
321 try {
322 writeBytes(b, 0, b.length, append);
323 bytesWritten = b.length;
324 } finally {
325 IoTrace.fileWriteEnd(traceContext, bytesWritten);
326 }
327 }
328
329 /**
330 * Writes <code>len</code> bytes from the specified byte array
331 * starting at offset <code>off</code> to this file output stream.
332 *
333 * @param b the data.
334 * @param off the start offset in the data.
335 * @param len the number of bytes to write.
336 * @exception IOException if an I/O error occurs.
337 */
338 public void write(byte b[], int off, int len) throws IOException {
339 Object traceContext = IoTrace.fileWriteBegin(path);
340 int bytesWritten = 0;
341 try {
342 writeBytes(b, off, len, append);
343 bytesWritten = len;
344 } finally {
345 IoTrace.fileWriteEnd(traceContext, bytesWritten);
346 }
347 }
348
349 /**
350 * Closes this file output stream and releases any system resources
351 * associated with this stream. This file output stream may no longer
352 * be used for writing bytes.
353 *
354 * <p> If this stream has an associated channel then the channel is closed
355 * as well.
356 *
357 * @exception IOException if an I/O error occurs.
358 *
359 * @revised 1.4
360 * @spec JSR-51
361 */
362 public void close() throws IOException {
363 synchronized (closeLock) {
364 if (closed) {
365 return;
366 }
367 closed = true;
368 }
369
370 if (channel != null) {
371 /*
372 * Decrement FD use count associated with the channel
373 * The use count is incremented whenever a new channel
374 * is obtained from this stream.
375 */
376 fd.decrementAndGetUseCount();
377 channel.close();
378 }
379
380 /*
381 * Decrement FD use count associated with this stream
382 */
383 int useCount = fd.decrementAndGetUseCount();
384
385 /*
386 * If FileDescriptor is still in use by another stream, the finalizer
387 * will not close it.
388 */
389 if ((useCount <= 0) || !isRunningFinalize()) {
390 close0();
391 }
392 }
393
394 /**
395 * Returns the file descriptor associated with this stream.
396 *
397 * @return the <code>FileDescriptor</code> object that represents
398 * the connection to the file in the file system being used
399 * by this <code>FileOutputStream</code> object.
400 *
401 * @exception IOException if an I/O error occurs.
402 * @see java.io.FileDescriptor
403 */
404 public final FileDescriptor getFD() throws IOException {
405 if (fd != null) return fd;
406 throw new IOException();
407 }
408
409 /**
410 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
411 * object associated with this file output stream. </p>
412 *
413 * <p> The initial {@link java.nio.channels.FileChannel#position()
414 * </code>position<code>} of the returned channel will be equal to the
415 * number of bytes written to the file so far unless this stream is in
416 * append mode, in which case it will be equal to the size of the file.
417 * Writing bytes to this stream will increment the channel's position
418 * accordingly. Changing the channel's position, either explicitly or by
419 * writing, will change this stream's file position.
420 *
421 * @return the file channel associated with this file output stream
422 *
423 * @since 1.4
424 * @spec JSR-51
425 */
426 public FileChannel getChannel() {
427 synchronized (this) {
428 if (channel == null) {
429 channel = FileChannelImpl.open(fd, path, false, true, append, this);
430
431 /*
432 * Increment fd's use count. Invoking the channel's close()
433 * method will result in decrementing the use count set for
434 * the channel.
435 */
436 fd.incrementAndGetUseCount();
437 }
438 return channel;
439 }
440 }
441
442 /**
443 * Cleans up the connection to the file, and ensures that the
444 * <code>close</code> method of this file output stream is
445 * called when there are no more references to this stream.
446 *
447 * @exception IOException if an I/O error occurs.
448 * @see java.io.FileInputStream#close()
449 */
450 protected void finalize() throws IOException {
451 if (fd != null) {
452 if (fd == FileDescriptor.out || fd == FileDescriptor.err) {
453 flush();
454 } else {
455
456 /*
457 * Finalizer should not release the FileDescriptor if another
458 * stream is still using it. If the user directly invokes
459 * close() then the FileDescriptor is also released.
460 */
461 runningFinalize.set(Boolean.TRUE);
462 try {
463 close();
464 } finally {
465 runningFinalize.set(Boolean.FALSE);
466 }
467 }
468 }
469 }
470
471 private native void close0() throws IOException;
472
473 private static native void initIDs();
474
475 static {
476 initIDs();
477 }
478
479 }