1 /*
2 * Copyright 1994-2007 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any 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 * @since JDK1.0
46 */
47 public
48 class FileInputStream extends InputStream
49 {
50 /* File Descriptor - handle to the open file */
51 private final FileDescriptor fd;
52
53 private FileChannel channel = null;
54
55 private final Object closeLock = new Object();
56 private volatile boolean closed = false;
57
58 private static final ThreadLocal<Boolean> runningFinalize =
59 new ThreadLocal<Boolean>();
60
61 private static boolean isRunningFinalize() {
62 Boolean val;
63 if ((val = runningFinalize.get()) != null)
64 return val.booleanValue();
65 return false;
66 }
67
68 /**
69 * Creates a <code>FileInputStream</code> by
70 * opening a connection to an actual file,
71 * the file named by the path name <code>name</code>
72 * in the file system. A new <code>FileDescriptor</code>
73 * object is created to represent this file
74 * connection.
75 * <p>
76 * First, if there is a security
77 * manager, its <code>checkRead</code> method
78 * is called with the <code>name</code> argument
79 * as its argument.
80 * <p>
81 * If the named file does not exist, is a directory rather than a regular
82 * file, or for some other reason cannot be opened for reading then a
83 * <code>FileNotFoundException</code> is thrown.
84 *
85 * @param name the system-dependent file name.
86 * @exception FileNotFoundException if the file does not exist,
87 * is a directory rather than a regular file,
88 * or for some other reason cannot be opened for
89 * reading.
90 * @exception SecurityException if a security manager exists and its
91 * <code>checkRead</code> method denies read access
92 * to the file.
93 * @see java.lang.SecurityManager#checkRead(java.lang.String)
94 */
95 public FileInputStream(String name) throws FileNotFoundException {
96 this(name != null ? new File(name) : null);
97 }
98
99 /**
100 * Creates a <code>FileInputStream</code> by
101 * opening a connection to an actual file,
102 * the file named by the <code>File</code>
103 * object <code>file</code> in the file system.
104 * A new <code>FileDescriptor</code> object
105 * is created to represent this file connection.
106 * <p>
107 * First, if there is a security manager,
108 * its <code>checkRead</code> method is called
109 * with the path represented by the <code>file</code>
110 * argument as its argument.
111 * <p>
112 * If the named file does not exist, is a directory rather than a regular
113 * file, or for some other reason cannot be opened for reading then a
114 * <code>FileNotFoundException</code> is thrown.
115 *
116 * @param file the file to be opened for reading.
117 * @exception FileNotFoundException if the file does not exist,
118 * is a directory rather than a regular file,
119 * or for some other reason cannot be opened for
120 * reading.
121 * @exception SecurityException if a security manager exists and its
122 * <code>checkRead</code> method denies read access to the file.
123 * @see java.io.File#getPath()
124 * @see java.lang.SecurityManager#checkRead(java.lang.String)
125 */
126 public FileInputStream(File file) throws FileNotFoundException {
127 String name = (file != null ? file.getPath() : null);
128 SecurityManager security = System.getSecurityManager();
129 if (security != null) {
130 security.checkRead(name);
131 }
132 if (name == null) {
133 throw new NullPointerException();
134 }
135 fd = new FileDescriptor();
136 fd.incrementAndGetUseCount();
137 open(name);
138 }
139
140 /**
141 * Creates a <code>FileInputStream</code> by using the file descriptor
142 * <code>fdObj</code>, which represents an existing connection to an
143 * actual file in the file system.
144 * <p>
145 * If there is a security manager, its <code>checkRead</code> method is
146 * called with the file descriptor <code>fdObj</code> as its argument to
147 * see if it's ok to read the file descriptor. If read access is denied
148 * to the file descriptor a <code>SecurityException</code> is thrown.
149 * <p>
150 * If <code>fdObj</code> is null then a <code>NullPointerException</code>
151 * is thrown.
152 * <p>
153 * This constructor does not throw an exception if <code>fdObj</code>
154 * is {@link java.io.FileDescriptor#valid() invalid}.
155 * However, if the methods are invoked on the resulting stream to attempt
156 * I/O on the stream, an <code>IOException</code> is thrown.
157 *
158 * @param fdObj the file descriptor to be opened for reading.
159 * @throws SecurityException if a security manager exists and its
160 * <code>checkRead</code> method denies read access to the
161 * file descriptor.
162 * @see SecurityManager#checkRead(java.io.FileDescriptor)
163 */
164 public FileInputStream(FileDescriptor fdObj) {
165 SecurityManager security = System.getSecurityManager();
166 if (fdObj == null) {
167 throw new NullPointerException();
168 }
169 if (security != null) {
170 security.checkRead(fdObj);
171 }
172 fd = fdObj;
173
174 /*
175 * FileDescriptor is being shared by streams.
176 * Ensure that it's GC'ed only when all the streams/channels are done
177 * using it.
178 */
179 fd.incrementAndGetUseCount();
180 }
181
182 /**
183 * Opens the specified file for reading.
184 * @param name the name of the file
185 */
186 private native void open(String name) throws FileNotFoundException;
187
188 /**
189 * Reads a byte of data from this input stream. This method blocks
190 * if no input is yet available.
191 *
192 * @return the next byte of data, or <code>-1</code> if the end of the
193 * file is reached.
194 * @exception IOException if an I/O error occurs.
195 */
196 public native int read() throws IOException;
197
198 /**
199 * Reads a subarray as a sequence of bytes.
200 * @param b the data to be written
201 * @param off the start offset in the data
202 * @param len the number of bytes that are written
203 * @exception IOException If an I/O error has occurred.
204 */
205 private native int readBytes(byte b[], int off, int len) throws IOException;
206
207 /**
208 * Reads up to <code>b.length</code> bytes of data from this input
209 * stream into an array of bytes. This method blocks until some input
210 * is available.
211 *
212 * @param b the buffer into which the data is read.
213 * @return the total number of bytes read into the buffer, or
214 * <code>-1</code> if there is no more data because the end of
215 * the file has been reached.
216 * @exception IOException if an I/O error occurs.
217 */
218 public int read(byte b[]) throws IOException {
219 return readBytes(b, 0, b.length);
220 }
221
222 /**
223 * Reads up to <code>len</code> bytes of data from this input stream
224 * into an array of bytes. If <code>len</code> is not zero, the method
225 * blocks until some input is available; otherwise, no
226 * bytes are read and <code>0</code> is returned.
227 *
228 * @param b the buffer into which the data is read.
229 * @param off the start offset in the destination array <code>b</code>
230 * @param len the maximum number of bytes read.
231 * @return the total number of bytes read into the buffer, or
232 * <code>-1</code> if there is no more data because the end of
233 * the file has been reached.
234 * @exception NullPointerException If <code>b</code> is <code>null</code>.
235 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
236 * <code>len</code> is negative, or <code>len</code> is greater than
237 * <code>b.length - off</code>
238 * @exception IOException if an I/O error occurs.
239 */
240 public int read(byte b[], int off, int len) throws IOException {
241 return readBytes(b, off, len);
242 }
243
244 /**
245 * Skips over and discards <code>n</code> bytes of data from the
246 * input stream.
247 *
248 * <p>The <code>skip</code> method may, for a variety of
249 * reasons, end up skipping over some smaller number of bytes,
250 * possibly <code>0</code>. If <code>n</code> is negative, an
251 * <code>IOException</code> is thrown, even though the <code>skip</code>
252 * method of the {@link InputStream} superclass does nothing in this case.
253 * The actual number of bytes skipped is returned.
254 *
255 * <p>This method may skip more bytes than are remaining in the backing
256 * file. This produces no exception and the number of bytes skipped
257 * may include some number of bytes that were beyond the EOF of the
258 * backing file. Attempting to read from the stream after skipping past
259 * the end will result in -1 indicating the end of the file.
260 *
261 * @param n the number of bytes to be skipped.
262 * @return the actual number of bytes skipped.
263 * @exception IOException if n is negative, if the stream does not
264 * support seek, or if an I/O error occurs.
265 */
266 public native long skip(long n) throws IOException;
267
268 /**
269 * Returns an estimate of the number of remaining bytes that can be read (or
270 * skipped over) from this input stream without blocking by the next
271 * invocation of a method for this input stream. The next invocation might be
272 * the same thread or another thread. A single read or skip of this
273 * many bytes will not block, but may read or skip fewer bytes.
274 *
275 * <p> In some cases, a non-blocking read (or skip) may appear to be
276 * blocked when it is merely slow, for example when reading large
277 * files over slow networks.
278 *
279 * @return an estimate of the number of remaining bytes that can be read
280 * (or skipped over) from this input stream without blocking.
281 * @exception IOException if this file input stream has been closed by calling
282 * {@code close} or an I/O error occurs.
283 */
284 public native int available() throws IOException;
285
286 /**
287 * Closes this file input stream and releases any system resources
288 * associated with the stream.
289 *
290 * <p> If this stream has an associated channel then the channel is closed
291 * as well.
292 *
293 * @exception IOException if an I/O error occurs.
294 *
295 * @revised 1.4
296 * @spec JSR-51
297 */
298 public void close() throws IOException {
299 synchronized (closeLock) {
300 if (closed) {
301 return;
302 }
303 closed = true;
304 }
305 if (channel != null) {
306 /*
307 * Decrement the FD use count associated with the channel
308 * The use count is incremented whenever a new channel
309 * is obtained from this stream.
310 */
311 fd.decrementAndGetUseCount();
312 channel.close();
313 }
314
315 /*
316 * Decrement the FD use count associated with this stream
317 */
318 int useCount = fd.decrementAndGetUseCount();
319
320 /*
321 * If FileDescriptor is still in use by another stream, the finalizer
322 * will not close it.
323 */
324 if ((useCount <= 0) || !isRunningFinalize()) {
325 close0();
326 }
327 }
328
329 /**
330 * Returns the <code>FileDescriptor</code>
331 * object that represents the connection to
332 * the actual file in the file system being
333 * used by this <code>FileInputStream</code>.
334 *
335 * @return the file descriptor object associated with this stream.
336 * @exception IOException if an I/O error occurs.
337 * @see java.io.FileDescriptor
338 */
339 public final FileDescriptor getFD() throws IOException {
340 if (fd != null) return fd;
341 throw new IOException();
342 }
343
344 /**
345 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
346 * object associated with this file input stream.
347 *
348 * <p> The initial {@link java.nio.channels.FileChannel#position()
349 * </code>position<code>} of the returned channel will be equal to the
350 * number of bytes read from the file so far. Reading bytes from this
351 * stream will increment the channel's position. Changing the channel's
352 * position, either explicitly or by reading, will change this stream's
353 * file position.
354 *
355 * @return the file channel associated with this file input stream
356 *
357 * @since 1.4
358 * @spec JSR-51
359 */
360 public FileChannel getChannel() {
361 synchronized (this) {
362 if (channel == null) {
363 channel = FileChannelImpl.open(fd, true, false, this);
364
365 /*
366 * Increment fd's use count. Invoking the channel's close()
367 * method will result in decrementing the use count set for
368 * the channel.
369 */
370 fd.incrementAndGetUseCount();
371 }
372 return channel;
373 }
374 }
375
376 private static native void initIDs();
377
378 private native void close0() throws IOException;
379
380 static {
381 initIDs();
382 }
383
384 /**
385 * Ensures that the <code>close</code> method of this file input stream is
386 * called when there are no more references to it.
387 *
388 * @exception IOException if an I/O error occurs.
389 * @see java.io.FileInputStream#close()
390 */
391 protected void finalize() throws IOException {
392 if ((fd != null) && (fd != FileDescriptor.in)) {
393
394 /*
395 * Finalizer should not release the FileDescriptor if another
396 * stream is still using it. If the user directly invokes
397 * close() then the FileDescriptor is also released.
398 */
399 runningFinalize.set(Boolean.TRUE);
400 try {
401 close();
402 } finally {
403 runningFinalize.set(Boolean.FALSE);
404 }
405 }
406 }
407 }
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