1 /*
2 * Copyright (c) 1994, 2013, 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 /**
55 * The path of the referenced file
56 * (null if the stream is created with a file descriptor)
57 */
58 private final String path;
59
60 private FileChannel channel = null;
61
62 private final Object closeLock = new Object();
63 private volatile boolean closed = false;
64
65 /**
66 * Creates a <code>FileInputStream</code> by
67 * opening a connection to an actual file,
68 * the file named by the path name <code>name</code>
69 * in the file system. A new <code>FileDescriptor</code>
70 * object is created to represent this file
71 * connection.
72 * <p>
73 * First, if there is a security
74 * manager, its <code>checkRead</code> method
75 * is called with the <code>name</code> argument
76 * as its argument.
77 * <p>
78 * If the named file does not exist, is a directory rather than a regular
79 * file, or for some other reason cannot be opened for reading then a
80 * <code>FileNotFoundException</code> is thrown.
81 *
82 * @param name the system-dependent file name.
83 * @exception FileNotFoundException if the file does not exist,
84 * is a directory rather than a regular file,
85 * or for some other reason cannot be opened for
86 * reading.
87 * @exception SecurityException if a security manager exists and its
88 * <code>checkRead</code> method denies read access
89 * to the file.
90 * @see java.lang.SecurityManager#checkRead(java.lang.String)
91 */
92 public FileInputStream(String name) throws FileNotFoundException {
93 this(name != null ? new File(name) : null);
94 }
95
96 /**
97 * Creates a <code>FileInputStream</code> by
98 * opening a connection to an actual file,
99 * the file named by the <code>File</code>
100 * object <code>file</code> in the file system.
101 * A new <code>FileDescriptor</code> object
102 * is created to represent this file connection.
103 * <p>
104 * First, if there is a security manager,
105 * its <code>checkRead</code> method is called
106 * with the path represented by the <code>file</code>
107 * argument as its argument.
108 * <p>
109 * If the named file does not exist, is a directory rather than a regular
110 * file, or for some other reason cannot be opened for reading then a
111 * <code>FileNotFoundException</code> is thrown.
112 *
113 * @param file the file to be opened for reading.
114 * @exception FileNotFoundException if the file does not exist,
115 * is a directory rather than a regular file,
116 * or for some other reason cannot be opened for
117 * reading.
118 * @exception SecurityException if a security manager exists and its
119 * <code>checkRead</code> method denies read access to the file.
120 * @see java.io.File#getPath()
121 * @see java.lang.SecurityManager#checkRead(java.lang.String)
122 */
123 public FileInputStream(File file) throws FileNotFoundException {
124 String name = (file != null ? file.getPath() : null);
125 SecurityManager security = System.getSecurityManager();
126 if (security != null) {
127 security.checkRead(name);
128 }
129 if (name == null) {
130 throw new NullPointerException();
131 }
132 if (file.isInvalid()) {
133 throw new FileNotFoundException("Invalid file path");
134 }
135 fd = new FileDescriptor();
136 fd.attach(this);
137 path = name;
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 path = null;
175
176 /*
177 * FileDescriptor is being shared by streams.
178 * Register this stream with FileDescriptor tracker.
179 */
180 fd.attach(this);
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, the method
252 * will try to skip backwards. In case the backing file does not support
253 * backward skip at its current position, an <code>IOException</code> is
254 * thrown. The actual number of bytes skipped is returned. If it skips
255 * forwards, it returns a positive value. If it skips backwards, it
256 * returns a negative value.
257 *
258 * <p>This method may skip more bytes than what are remaining in the
259 * backing file. This produces no exception and the number of bytes skipped
260 * may include some number of bytes that were beyond the EOF of the
261 * backing file. Attempting to read from the stream after skipping past
262 * the end will result in -1 indicating the end of the file.
263 *
264 * @param n the number of bytes to be skipped.
265 * @return the actual number of bytes skipped.
266 * @exception IOException if n is negative, if the stream does not
267 * support seek, or if an I/O error occurs.
268 */
269 public native long skip(long n) throws IOException;
270
271 /**
272 * Returns an estimate of the number of remaining bytes that can be read (or
273 * skipped over) from this input stream without blocking by the next
274 * invocation of a method for this input stream. Returns 0 when the file
275 * position is beyond EOF. The next invocation might be the same thread
276 * or another thread. A single read or skip of this many bytes will not
277 * block, but may read or skip fewer bytes.
278 *
279 * <p> In some cases, a non-blocking read (or skip) may appear to be
280 * blocked when it is merely slow, for example when reading large
281 * files over slow networks.
282 *
283 * @return an estimate of the number of remaining bytes that can be read
284 * (or skipped over) from this input stream without blocking.
285 * @exception IOException if this file input stream has been closed by calling
286 * {@code close} or an I/O error occurs.
287 */
288 public native int available() throws IOException;
289
290 /**
291 * Closes this file input stream and releases any system resources
292 * associated with the stream.
293 *
294 * <p> If this stream has an associated channel then the channel is closed
295 * as well.
296 *
297 * @exception IOException if an I/O error occurs.
298 *
299 * @revised 1.4
300 * @spec JSR-51
301 */
302 public void close() throws IOException {
303 synchronized (closeLock) {
304 if (closed) {
305 return;
306 }
307 closed = true;
308 }
309 if (channel != null) {
310 channel.close();
311 }
312
313 fd.closeAll(new Closeable() {
314 public void close() throws IOException {
315 close0();
316 }
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) {
332 return fd;
333 }
334 throw new IOException();
335 }
336
337 /**
338 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
339 * object associated with this file input stream.
340 *
341 * <p> The initial {@link java.nio.channels.FileChannel#position()
342 * position} of the returned channel will be equal to the
343 * number of bytes read from the file so far. Reading bytes from this
344 * stream will increment the channel's position. Changing the channel's
345 * position, either explicitly or by reading, will change this stream's
346 * file position.
347 *
348 * @return the file channel associated with this file input stream
349 *
350 * @since 1.4
351 * @spec JSR-51
352 */
353 public FileChannel getChannel() {
354 synchronized (this) {
355 if (channel == null) {
356 channel = FileChannelImpl.open(fd, path, true, false, this);
357 }
358 return channel;
359 }
360 }
361
362 private static native void initIDs();
363
364 private native void close0() throws IOException;
365
366 static {
367 initIDs();
368 }
369
370 /**
371 * Ensures that the <code>close</code> method of this file input stream is
372 * called when there are no more references to it.
373 *
374 * @exception IOException if an I/O error occurs.
375 * @see java.io.FileInputStream#close()
376 */
377 protected void finalize() throws IOException {
378 if ((fd != null) && (fd != FileDescriptor.in)) {
379 /* if fd is shared, the references in FileDescriptor
380 * will ensure that finalizer is only called when
381 * safe to do so. All references using the fd have
382 * become unreachable. We can call close()
383 */
384 close();
385 }
386 }
387 }