1 /*
2 * Copyright (c) 1994, 2017, 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 <code>FileInputStream</code> obtains input bytes
34 * from a file in a file system. What files
35 * are available depends on the host environment.
36 *
37 * <p><code>FileInputStream</code> is meant for reading streams of raw bytes
38 * such as image data. For reading streams of characters, consider using
39 * <code>FileReader</code>.
40 *
41 * @apiNote
42 * To release resources used by this stream {@link #close} should be called
43 * directly or by try-with-resources. Subclasses are responsible for the cleanup
44 * of resources acquired by the subclass.
45 * Subclasses that override {@link #finalize} in order to perform cleanup
46 * should be modified to use alternative cleanup mechanisms such as
47 * {@link java.lang.ref.Cleaner} and remove the overriding {@code finalize} method.
48 *
49 * @implSpec
50 * If this FileInputStream has been subclassed and the {@link #close}
51 * method has been overridden, the {@link #close} method will be
52 * called when the FileInputStream is unreachable.
53 * Otherwise, it is implementation specific how the resource cleanup described in
54 * {@link #close} is performed.
55
56 *
57 * @author Arthur van Hoff
58 * @see java.io.File
59 * @see java.io.FileDescriptor
60 * @see java.io.FileOutputStream
61 * @see java.nio.file.Files#newInputStream
62 * @since 1.0
63 */
64 public
65 class FileInputStream extends InputStream
66 {
67 /* File Descriptor - handle to the open file */
68 private final FileDescriptor fd;
69
70 /**
71 * The path of the referenced file
72 * (null if the stream is created with a file descriptor)
73 */
74 private final String path;
75
76 private volatile FileChannel channel;
77
78 private final Object closeLock = new Object();
79
80 private volatile boolean closed;
81
82 private final Object altFinalizer;
83
84 /**
85 * Creates a <code>FileInputStream</code> by
86 * opening a connection to an actual file,
87 * the file named by the path name <code>name</code>
88 * in the file system. A new <code>FileDescriptor</code>
89 * object is created to represent this file
90 * connection.
91 * <p>
92 * First, if there is a security
93 * manager, its <code>checkRead</code> method
94 * is called with the <code>name</code> argument
95 * as its argument.
96 * <p>
97 * If the named file does not exist, is a directory rather than a regular
98 * file, or for some other reason cannot be opened for reading then a
99 * <code>FileNotFoundException</code> is thrown.
100 *
101 * @param name the system-dependent file name.
102 * @exception FileNotFoundException if the file does not exist,
103 * is a directory rather than a regular file,
104 * or for some other reason cannot be opened for
105 * reading.
106 * @exception SecurityException if a security manager exists and its
107 * <code>checkRead</code> method denies read access
108 * to the file.
109 * @see java.lang.SecurityManager#checkRead(java.lang.String)
110 */
111 public FileInputStream(String name) throws FileNotFoundException {
112 this(name != null ? new File(name) : null);
113 }
114
115 /**
116 * Creates a <code>FileInputStream</code> by
117 * opening a connection to an actual file,
118 * the file named by the <code>File</code>
119 * object <code>file</code> in the file system.
120 * A new <code>FileDescriptor</code> object
121 * is created to represent this file connection.
122 * <p>
123 * First, if there is a security manager,
124 * its <code>checkRead</code> method is called
125 * with the path represented by the <code>file</code>
126 * argument as its argument.
127 * <p>
128 * If the named file does not exist, is a directory rather than a regular
129 * file, or for some other reason cannot be opened for reading then a
130 * <code>FileNotFoundException</code> is thrown.
131 *
132 * @param file the file to be opened for reading.
133 * @exception FileNotFoundException if the file does not exist,
134 * is a directory rather than a regular file,
135 * or for some other reason cannot be opened for
136 * reading.
137 * @exception SecurityException if a security manager exists and its
138 * <code>checkRead</code> method denies read access to the file.
139 * @see java.io.File#getPath()
140 * @see java.lang.SecurityManager#checkRead(java.lang.String)
141 */
142 public FileInputStream(File file) throws FileNotFoundException {
143 String name = (file != null ? file.getPath() : null);
144 SecurityManager security = System.getSecurityManager();
145 if (security != null) {
146 security.checkRead(name);
147 }
148 if (name == null) {
149 throw new NullPointerException();
150 }
151 if (file.isInvalid()) {
152 throw new FileNotFoundException("Invalid file path");
153 }
154 fd = new FileDescriptor();
155 fd.attach(this);
156 path = name;
157 open(name);
158 altFinalizer = getFinalizer(this);
159 if (altFinalizer == null) {
160 FileCleanable.register(fd); // open set the fd, register the cleanup
161 }
162 }
163
164 /**
165 * Creates a <code>FileInputStream</code> by using the file descriptor
166 * <code>fdObj</code>, which represents an existing connection to an
167 * actual file in the file system.
168 * <p>
169 * If there is a security manager, its <code>checkRead</code> method is
170 * called with the file descriptor <code>fdObj</code> as its argument to
171 * see if it's ok to read the file descriptor. If read access is denied
172 * to the file descriptor a <code>SecurityException</code> is thrown.
173 * <p>
174 * If <code>fdObj</code> is null then a <code>NullPointerException</code>
175 * is thrown.
176 * <p>
177 * This constructor does not throw an exception if <code>fdObj</code>
178 * is {@link java.io.FileDescriptor#valid() invalid}.
179 * However, if the methods are invoked on the resulting stream to attempt
180 * I/O on the stream, an <code>IOException</code> is thrown.
181 *
182 * @param fdObj the file descriptor to be opened for reading.
183 * @throws SecurityException if a security manager exists and its
184 * <code>checkRead</code> method denies read access to the
185 * file descriptor.
186 * @see SecurityManager#checkRead(java.io.FileDescriptor)
187 */
188 public FileInputStream(FileDescriptor fdObj) {
189 SecurityManager security = System.getSecurityManager();
190 if (fdObj == null) {
191 throw new NullPointerException();
192 }
193 if (security != null) {
194 security.checkRead(fdObj);
195 }
196 fd = fdObj;
197 path = null;
198 altFinalizer = null;
199
200 /*
201 * FileDescriptor is being shared by streams.
202 * Register this stream with FileDescriptor tracker.
203 */
204 fd.attach(this);
205 }
206
207 /**
208 * Opens the specified file for reading.
209 * @param name the name of the file
210 */
211 private native void open0(String name) throws FileNotFoundException;
212
213 // wrap native call to allow instrumentation
214 /**
215 * Opens the specified file for reading.
216 * @param name the name of the file
217 */
218 private void open(String name) throws FileNotFoundException {
219 open0(name);
220 }
221
222 /**
223 * Reads a byte of data from this input stream. This method blocks
224 * if no input is yet available.
225 *
226 * @return the next byte of data, or <code>-1</code> if the end of the
227 * file is reached.
228 * @exception IOException if an I/O error occurs.
229 */
230 public int read() throws IOException {
231 return read0();
232 }
233
234 private native int read0() throws IOException;
235
236 /**
237 * Reads a subarray as a sequence of bytes.
238 * @param b the data to be written
239 * @param off the start offset in the data
240 * @param len the number of bytes that are written
241 * @exception IOException If an I/O error has occurred.
242 */
243 private native int readBytes(byte b[], int off, int len) throws IOException;
244
245 /**
246 * Reads up to <code>b.length</code> bytes of data from this input
247 * stream into an array of bytes. This method blocks until some input
248 * is available.
249 *
250 * @param b the buffer into which the data is read.
251 * @return the total number of bytes read into the buffer, or
252 * <code>-1</code> if there is no more data because the end of
253 * the file has been reached.
254 * @exception IOException if an I/O error occurs.
255 */
256 public int read(byte b[]) throws IOException {
257 return readBytes(b, 0, b.length);
258 }
259
260 /**
261 * Reads up to <code>len</code> bytes of data from this input stream
262 * into an array of bytes. If <code>len</code> is not zero, the method
263 * blocks until some input is available; otherwise, no
264 * bytes are read and <code>0</code> is returned.
265 *
266 * @param b the buffer into which the data is read.
267 * @param off the start offset in the destination array <code>b</code>
268 * @param len the maximum number of bytes read.
269 * @return the total number of bytes read into the buffer, or
270 * <code>-1</code> if there is no more data because the end of
271 * the file has been reached.
272 * @exception NullPointerException If <code>b</code> is <code>null</code>.
273 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
274 * <code>len</code> is negative, or <code>len</code> is greater than
275 * <code>b.length - off</code>
276 * @exception IOException if an I/O error occurs.
277 */
278 public int read(byte b[], int off, int len) throws IOException {
279 return readBytes(b, off, len);
280 }
281
282 /**
283 * Skips over and discards <code>n</code> bytes of data from the
284 * input stream.
285 *
286 * <p>The <code>skip</code> method may, for a variety of
287 * reasons, end up skipping over some smaller number of bytes,
288 * possibly <code>0</code>. If <code>n</code> is negative, the method
289 * will try to skip backwards. In case the backing file does not support
290 * backward skip at its current position, an <code>IOException</code> is
291 * thrown. The actual number of bytes skipped is returned. If it skips
292 * forwards, it returns a positive value. If it skips backwards, it
293 * returns a negative value.
294 *
295 * <p>This method may skip more bytes than what are remaining in the
296 * backing file. This produces no exception and the number of bytes skipped
297 * may include some number of bytes that were beyond the EOF of the
298 * backing file. Attempting to read from the stream after skipping past
299 * the end will result in -1 indicating the end of the file.
300 *
301 * @param n the number of bytes to be skipped.
302 * @return the actual number of bytes skipped.
303 * @exception IOException if n is negative, if the stream does not
304 * support seek, or if an I/O error occurs.
305 */
306 public long skip(long n) throws IOException {
307 return skip0(n);
308 }
309
310 private native long skip0(long n) throws IOException;
311
312 /**
313 * Returns an estimate of the number of remaining bytes that can be read (or
314 * skipped over) from this input stream without blocking by the next
315 * invocation of a method for this input stream. Returns 0 when the file
316 * position is beyond EOF. The next invocation might be the same thread
317 * or another thread. A single read or skip of this many bytes will not
318 * block, but may read or skip fewer bytes.
319 *
320 * <p> In some cases, a non-blocking read (or skip) may appear to be
321 * blocked when it is merely slow, for example when reading large
322 * files over slow networks.
323 *
324 * @return an estimate of the number of remaining bytes that can be read
325 * (or skipped over) from this input stream without blocking.
326 * @exception IOException if this file input stream has been closed by calling
327 * {@code close} or an I/O error occurs.
328 */
329 public int available() throws IOException {
330 return available0();
331 }
332
333 private native int available0() throws IOException;
334
335 /**
336 * Closes this file input stream and releases any system resources
337 * associated with the stream.
338 *
339 * <p> If this stream has an associated channel then the channel is closed
340 * as well.
341 *
342 * @apiNote
343 * Overriding {@link #close} to perform cleanup actions is reliable
344 * only when called directly or when called by try-with-resources.
345 * Do not depend on finalization to invoke {@code close};
346 * finalization is not reliable and is deprecated.
347 * If cleanup of native resources is needed, other mechanisms such as
348 * {@linkplain java.lang.ref.Cleaner} should be used.
349 *
350 * @exception IOException if an I/O error occurs.
351 *
352 * @revised 1.4
353 * @spec JSR-51
354 */
355 public void close() throws IOException {
356 if (closed) {
357 return;
358 }
359 synchronized (closeLock) {
360 if (closed) {
361 return;
362 }
363 closed = true;
364 }
365
366 FileChannel fc = channel;
367 if (fc != null) {
368 // possible race with getChannel(), benign since
369 // FileChannel.close is final and idempotent
370 fc.close();
371 }
372
373 fd.closeAll(new Closeable() {
374 public void close() throws IOException {
375 fd.close();
376 }
377 });
378 }
379
380 /**
381 * Returns the <code>FileDescriptor</code>
382 * object that represents the connection to
383 * the actual file in the file system being
384 * used by this <code>FileInputStream</code>.
385 *
386 * @return the file descriptor object associated with this stream.
387 * @exception IOException if an I/O error occurs.
388 * @see java.io.FileDescriptor
389 */
390 public final FileDescriptor getFD() throws IOException {
391 if (fd != null) {
392 return fd;
393 }
394 throw new IOException();
395 }
396
397 /**
398 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
399 * object associated with this file input stream.
400 *
401 * <p> The initial {@link java.nio.channels.FileChannel#position()
402 * position} of the returned channel will be equal to the
403 * number of bytes read from the file so far. Reading bytes from this
404 * stream will increment the channel's position. Changing the channel's
405 * position, either explicitly or by reading, will change this stream's
406 * file position.
407 *
408 * @return the file channel associated with this file input stream
409 *
410 * @since 1.4
411 * @spec JSR-51
412 */
413 public FileChannel getChannel() {
414 FileChannel fc = this.channel;
415 if (fc == null) {
416 synchronized (this) {
417 fc = this.channel;
418 if (fc == null) {
419 this.channel = fc = FileChannelImpl.open(fd, path, true,
420 false, false, this);
421 if (closed) {
422 try {
423 // possible race with close(), benign since
424 // FileChannel.close is final and idempotent
425 fc.close();
426 } catch (IOException ioe) {
427 throw new InternalError(ioe); // should not happen
428 }
429 }
430 }
431 }
432 }
433 return fc;
434 }
435
436 private static native void initIDs();
437
438 static {
439 initIDs();
440 }
441
442 /**
443 * Ensures that the {@link #close} method of this file input stream is
444 * called when there are no more references to it.
445 * The {@link #finalize} method does not call {@link #close} directly.
446 *
447 * @apiNote
448 * To release resources used by this stream {@link #close} should be called
449 * directly or by try-with-resources.
450 *
451 * @implSpec
452 * If this FileInputStream has been subclassed and the {@link #close}
453 * method has been overridden, the {@link #close} method will be
454 * called when the FileInputStream is unreachable.
455 * Otherwise, it is implementation specific how the resource cleanup described in
456 * {@link #close} is performed.
457 *
458 * @deprecated The {@code finalize} method has been deprecated and will be removed.
459 * Subclasses that override {@code finalize} in order to perform cleanup
460 * should be modified to use alternative cleanup mechanisms and
461 * to remove the overriding {@code finalize} method.
462 * When overriding the {@code finalize} method, its implementation must explicitly
463 * ensure that {@code super.finalize()} is invoked as described in {@link Object#finalize}.
464 * See the specification for {@link Object#finalize()} for further
465 * information about migration options.
466 *
467 * @exception IOException if an I/O error occurs.
468 * @see java.io.FileInputStream#close()
469 */
470 @Deprecated(since="9", forRemoval = true)
471 protected void finalize() throws IOException {
472 }
473
474 /*
475 * Returns a finalizer object if the FIS needs a finalizer; otherwise null.
476 * If the FIS has a close method; it needs an AltFinalizer.
477 */
478 private static Object getFinalizer(FileInputStream fis) {
479 Class<?> clazz = fis.getClass();
480 while (clazz != FileInputStream.class) {
481 try {
482 clazz.getDeclaredMethod("close");
483 return new AltFinalizer(fis);
484 } catch (NoSuchMethodException nsme) {
485 // ignore
486 }
487 clazz = clazz.getSuperclass();
488 }
489 return null;
490 }
491 /**
492 * Class to call {@code FileInputStream.close} when finalized.
493 * If finalization of the stream is needed, an instance is created
494 * in its constructor(s). When the set of instances
495 * related to the stream is unreachable, the AltFinalizer performs
496 * the needed call to the stream's {@code close} method.
497 */
498 static class AltFinalizer {
499 private final FileInputStream fis;
500
501 AltFinalizer(FileInputStream fis) {
502 this.fis = fis;
503 }
504
505 @Override
506 @SuppressWarnings("deprecation")
507 protected final void finalize() {
508 try {
509 if ((fis.fd != null) && (fis.fd != FileDescriptor.in)) {
510 /* if fd is shared, the references in FileDescriptor
511 * will ensure that finalizer is only called when
512 * safe to do so. All references using the fd have
513 * become unreachable. We can call close()
514 */
515 fis.close();
516 }
517 } catch (IOException ioe) {
518 // ignore
519 }
520 }
521 }
522 }