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