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 <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 * @author Arthur van Hoff
42 * @see java.io.File
43 * @see java.io.FileDescriptor
44 * @see java.io.FileOutputStream
45 * @see java.nio.file.Files#newInputStream
46 * @since JDK1.0
47 */
48 public
49 class FileInputStream extends InputStream
50 {
51 /* File Descriptor - handle to the open file */
52 private final FileDescriptor fd;
53
54 private FileChannel channel = null;
55
56 private final Object closeLock = new Object();
57 private volatile boolean closed = false;
58
59 private static final ThreadLocal<Boolean> runningFinalize =
60 new ThreadLocal<>();
61
62 private static boolean isRunningFinalize() {
63 Boolean val;
64 if ((val = runningFinalize.get()) != null)
65 return val.booleanValue();
66 return false;
67 }
68
69 /**
70 * Creates a <code>FileInputStream</code> by
71 * opening a connection to an actual file,
72 * the file named by the path name <code>name</code>
73 * in the file system. A new <code>FileDescriptor</code>
74 * object is created to represent this file
75 * connection.
76 * <p>
77 * First, if there is a security
78 * manager, its <code>checkRead</code> method
79 * is called with the <code>name</code> argument
80 * as its argument.
81 * <p>
82 * If the named file does not exist, is a directory rather than a regular
83 * file, or for some other reason cannot be opened for reading then a
84 * <code>FileNotFoundException</code> is thrown.
85 *
86 * @param name the system-dependent file name.
87 * @exception FileNotFoundException if the file does not exist,
88 * is a directory rather than a regular file,
89 * or for some other reason cannot be opened for
90 * reading.
91 * @exception SecurityException if a security manager exists and its
92 * <code>checkRead</code> method denies read access
93 * to the file.
94 * @see java.lang.SecurityManager#checkRead(java.lang.String)
95 */
96 public FileInputStream(String name) throws FileNotFoundException {
97 this(name != null ? new File(name) : null);
98 }
99
100 /**
101 * Creates a <code>FileInputStream</code> by
102 * opening a connection to an actual file,
103 * the file named by the <code>File</code>
104 * object <code>file</code> in the file system.
105 * A new <code>FileDescriptor</code> object
106 * is created to represent this file connection.
107 * <p>
108 * First, if there is a security manager,
109 * its <code>checkRead</code> method is called
110 * with the path represented by the <code>file</code>
111 * argument as its argument.
112 * <p>
113 * If the named file does not exist, is a directory rather than a regular
114 * file, or for some other reason cannot be opened for reading then a
115 * <code>FileNotFoundException</code> is thrown.
116 *
117 * @param file the file to be opened for reading.
118 * @exception FileNotFoundException if the file does not exist,
119 * is a directory rather than a regular file,
120 * or for some other reason cannot be opened for
121 * reading.
122 * @exception SecurityException if a security manager exists and its
123 * <code>checkRead</code> method denies read access to the file.
124 * @see java.io.File#getPath()
125 * @see java.lang.SecurityManager#checkRead(java.lang.String)
126 */
127 public FileInputStream(File file) throws FileNotFoundException {
128 String name = (file != null ? file.getPath() : null);
129 SecurityManager security = System.getSecurityManager();
130 if (security != null) {
131 security.checkRead(name);
132 }
133 if (name == null) {
134 throw new NullPointerException();
135 }
136 fd = new FileDescriptor();
137 fd.incrementAndGetUseCount();
138 open(name);
139 }
140
141 /**
142 * Creates a <code>FileInputStream</code> by using the file descriptor
143 * <code>fdObj</code>, which represents an existing connection to an
144 * actual file in the file system.
145 * <p>
146 * If there is a security manager, its <code>checkRead</code> method is
147 * called with the file descriptor <code>fdObj</code> as its argument to
148 * see if it's ok to read the file descriptor. If read access is denied
149 * to the file descriptor a <code>SecurityException</code> is thrown.
150 * <p>
151 * If <code>fdObj</code> is null then a <code>NullPointerException</code>
152 * is thrown.
153 * <p>
154 * This constructor does not throw an exception if <code>fdObj</code>
155 * is {@link java.io.FileDescriptor#valid() invalid}.
156 * However, if the methods are invoked on the resulting stream to attempt
157 * I/O on the stream, an <code>IOException</code> is thrown.
158 *
159 * @param fdObj the file descriptor to be opened for reading.
160 * @throws SecurityException if a security manager exists and its
161 * <code>checkRead</code> method denies read access to the
162 * file descriptor.
163 * @see SecurityManager#checkRead(java.io.FileDescriptor)
164 */
165 public FileInputStream(FileDescriptor fdObj) {
166 SecurityManager security = System.getSecurityManager();
167 if (fdObj == null) {
168 throw new NullPointerException();
169 }
170 if (security != null) {
171 security.checkRead(fdObj);
172 }
173 fd = fdObj;
174
175 /*
176 * FileDescriptor is being shared by streams.
177 * Ensure that it's GC'ed only when all the streams/channels are done
178 * using it.
179 */
180 fd.incrementAndGetUseCount();
181 }
182
183 /**
184 * Opens the specified file for reading.
185 * @param name the name of the file
186 */
187 private native void open(String name) throws FileNotFoundException;
188
189 /**
190 * Reads a byte of data from this input stream. This method blocks
191 * if no input is yet available.
192 *
193 * @return the next byte of data, or <code>-1</code> if the end of the
194 * file is reached.
195 * @exception IOException if an I/O error occurs.
196 */
197 public native int read() throws IOException;
198
199 /**
200 * Reads a subarray as a sequence of bytes.
201 * @param b the data to be written
202 * @param off the start offset in the data
203 * @param len the number of bytes that are written
204 * @exception IOException If an I/O error has occurred.
205 */
206 private native int readBytes(byte b[], int off, int len) throws IOException;
207
208 /**
209 * Reads up to <code>b.length</code> bytes of data from this input
210 * stream into an array of bytes. This method blocks until some input
211 * is available.
212 *
213 * @param b the buffer into which the data is read.
214 * @return the total number of bytes read into the buffer, or
215 * <code>-1</code> if there is no more data because the end of
216 * the file has been reached.
217 * @exception IOException if an I/O error occurs.
218 */
219 public int read(byte b[]) throws IOException {
220 return readBytes(b, 0, b.length);
221 }
222
223 /**
224 * Reads up to <code>len</code> bytes of data from this input stream
225 * into an array of bytes. If <code>len</code> is not zero, the method
226 * blocks until some input is available; otherwise, no
227 * bytes are read and <code>0</code> is returned.
228 *
229 * @param b the buffer into which the data is read.
230 * @param off the start offset in the destination array <code>b</code>
231 * @param len the maximum number of bytes read.
232 * @return the total number of bytes read into the buffer, or
233 * <code>-1</code> if there is no more data because the end of
234 * the file has been reached.
235 * @exception NullPointerException If <code>b</code> is <code>null</code>.
236 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
237 * <code>len</code> is negative, or <code>len</code> is greater than
238 * <code>b.length - off</code>
239 * @exception IOException if an I/O error occurs.
240 */
241 public int read(byte b[], int off, int len) throws IOException {
242 return readBytes(b, off, len);
243 }
244
245 /**
246 * Skips over and discards <code>n</code> bytes of data from the
247 * input stream.
248 *
249 * <p>The <code>skip</code> method may, for a variety of
250 * reasons, end up skipping over some smaller number of bytes,
251 * possibly <code>0</code>. If <code>n</code> is negative, an
252 * <code>IOException</code> is thrown, even though the <code>skip</code>
253 * method of the {@link InputStream} superclass does nothing in this case.
254 * The actual number of bytes skipped is returned.
255 *
256 * <p>This method may skip more bytes than are remaining in the backing
257 * file. This produces no exception and the number of bytes skipped
258 * may include some number of bytes that were beyond the EOF of the
259 * backing file. Attempting to read from the stream after skipping past
260 * the end will result in -1 indicating the end of the file.
261 *
262 * @param n the number of bytes to be skipped.
263 * @return the actual number of bytes skipped.
264 * @exception IOException if n is negative, if the stream does not
265 * support seek, or if an I/O error occurs.
266 */
267 public native long skip(long n) throws IOException;
268
269 /**
270 * Returns an estimate of the number of remaining bytes that can be read (or
271 * skipped over) from this input stream without blocking by the next
272 * invocation of a method for this input stream. The next invocation might be
273 * the same thread or another thread. A single read or skip of this
274 * many bytes will not block, but may read or skip fewer bytes.
275 *
276 * <p> In some cases, a non-blocking read (or skip) may appear to be
277 * blocked when it is merely slow, for example when reading large
278 * files over slow networks.
279 *
280 * @return an estimate of the number of remaining bytes that can be read
281 * (or skipped over) from this input stream without blocking.
282 * @exception IOException if this file input stream has been closed by calling
283 * {@code close} or an I/O error occurs.
284 */
285 public native int available() throws IOException;
286
287 /**
288 * Closes this file input stream and releases any system resources
289 * associated with the stream.
290 *
291 * <p> If this stream has an associated channel then the channel is closed
292 * as well.
293 *
294 * @exception IOException if an I/O error occurs.
295 *
296 * @revised 1.4
297 * @spec JSR-51
298 */
299 public void close() throws IOException {
300 synchronized (closeLock) {
301 if (closed) {
302 return;
303 }
304 closed = true;
305 }
306 if (channel != null) {
307 /*
308 * Decrement the FD use count associated with the channel
309 * The use count is incremented whenever a new channel
310 * is obtained from this stream.
311 */
312 fd.decrementAndGetUseCount();
313 channel.close();
314 }
315
316 /*
317 * Decrement the FD use count associated with this stream
318 */
319 int useCount = fd.decrementAndGetUseCount();
320
321 /*
322 * If FileDescriptor is still in use by another stream, the finalizer
323 * will not close it.
324 */
325 if ((useCount <= 0) || !isRunningFinalize()) {
326 close0();
327 }
328 }
329
330 /**
331 * Returns the <code>FileDescriptor</code>
332 * object that represents the connection to
333 * the actual file in the file system being
334 * used by this <code>FileInputStream</code>.
335 *
336 * @return the file descriptor object associated with this stream.
337 * @exception IOException if an I/O error occurs.
338 * @see java.io.FileDescriptor
339 */
340 public final FileDescriptor getFD() throws IOException {
341 if (fd != null) return fd;
342 throw new IOException();
343 }
344
345 /**
346 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
347 * object associated with this file input stream.
348 *
349 * <p> The initial {@link java.nio.channels.FileChannel#position()
350 * </code>position<code>} of the returned channel will be equal to the
351 * number of bytes read from the file so far. Reading bytes from this
352 * stream will increment the channel's position. Changing the channel's
353 * position, either explicitly or by reading, will change this stream's
354 * file position.
355 *
356 * @return the file channel associated with this file input stream
357 *
358 * @since 1.4
359 * @spec JSR-51
360 */
361 public FileChannel getChannel() {
362 synchronized (this) {
363 if (channel == null) {
364 channel = FileChannelImpl.open(fd, true, false, this);
365
366 /*
367 * Increment fd's use count. Invoking the channel's close()
368 * method will result in decrementing the use count set for
369 * the channel.
370 */
371 fd.incrementAndGetUseCount();
372 }
373 return channel;
374 }
375 }
376
377 private static native void initIDs();
378
379 private native void close0() throws IOException;
380
381 static {
382 initIDs();
383 }
384
385 /**
386 * Ensures that the <code>close</code> method of this file input stream is
387 * called when there are no more references to it.
388 *
389 * @exception IOException if an I/O error occurs.
390 * @see java.io.FileInputStream#close()
391 */
392 protected void finalize() throws IOException {
393 if ((fd != null) && (fd != FileDescriptor.in)) {
394
395 /*
396 * Finalizer should not release the FileDescriptor if another
397 * stream is still using it. If the user directly invokes
398 * close() then the FileDescriptor is also released.
399 */
400 runningFinalize.set(Boolean.TRUE);
401 try {
402 close();
403 } finally {
404 runningFinalize.set(Boolean.FALSE);
405 }
406 }
407 }
408 }