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 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 if (file.isInvalid()) {
127 throw new FileNotFoundException("Invalid file path");
128 }
129 fd = new FileDescriptor();
130 fd.attach(this);
131 open(name);
132 }
133
134 /**
135 * Creates a <code>FileInputStream</code> by using the file descriptor
136 * <code>fdObj</code>, which represents an existing connection to an
137 * actual file in the file system.
138 * <p>
139 * If there is a security manager, its <code>checkRead</code> method is
140 * called with the file descriptor <code>fdObj</code> as its argument to
141 * see if it's ok to read the file descriptor. If read access is denied
142 * to the file descriptor a <code>SecurityException</code> is thrown.
143 * <p>
144 * If <code>fdObj</code> is null then a <code>NullPointerException</code>
145 * is thrown.
146 * <p>
147 * This constructor does not throw an exception if <code>fdObj</code>
148 * is {@link java.io.FileDescriptor#valid() invalid}.
149 * However, if the methods are invoked on the resulting stream to attempt
150 * I/O on the stream, an <code>IOException</code> is thrown.
151 *
152 * @param fdObj the file descriptor to be opened for reading.
153 * @throws SecurityException if a security manager exists and its
154 * <code>checkRead</code> method denies read access to the
155 * file descriptor.
156 * @see SecurityManager#checkRead(java.io.FileDescriptor)
157 */
158 public FileInputStream(FileDescriptor fdObj) {
159 SecurityManager security = System.getSecurityManager();
160 if (fdObj == null) {
161 throw new NullPointerException();
162 }
163 if (security != null) {
164 security.checkRead(fdObj);
165 }
166 fd = fdObj;
167
168 /*
169 * FileDescriptor is being shared by streams.
170 * Register this stream with FileDescriptor tracker.
171 */
172 fd.attach(this);
173 }
174
175 /**
176 * Opens the specified file for reading.
177 * @param name the name of the file
178 */
179 private native void open(String name) throws FileNotFoundException;
180
181 /**
182 * Reads a byte of data from this input stream. This method blocks
183 * if no input is yet available.
184 *
185 * @return the next byte of data, or <code>-1</code> if the end of the
186 * file is reached.
187 * @exception IOException if an I/O error occurs.
188 */
189 public native int read() throws IOException;
190
191 /**
192 * Reads a subarray as a sequence of bytes.
193 * @param b the data to be written
194 * @param off the start offset in the data
195 * @param len the number of bytes that are written
196 * @exception IOException If an I/O error has occurred.
197 */
198 private native int readBytes(byte b[], int off, int len) throws IOException;
199
200 /**
201 * Reads up to <code>b.length</code> bytes of data from this input
202 * stream into an array of bytes. This method blocks until some input
203 * is available.
204 *
205 * @param b the buffer into which the data is read.
206 * @return the total number of bytes read into the buffer, or
207 * <code>-1</code> if there is no more data because the end of
208 * the file has been reached.
209 * @exception IOException if an I/O error occurs.
210 */
211 public int read(byte b[]) throws IOException {
212 return readBytes(b, 0, b.length);
213 }
214
215 /**
216 * Reads up to <code>len</code> bytes of data from this input stream
217 * into an array of bytes. If <code>len</code> is not zero, the method
218 * blocks until some input is available; otherwise, no
219 * bytes are read and <code>0</code> is returned.
220 *
221 * @param b the buffer into which the data is read.
222 * @param off the start offset in the destination array <code>b</code>
223 * @param len the maximum number of bytes read.
224 * @return the total number of bytes read into the buffer, or
225 * <code>-1</code> if there is no more data because the end of
226 * the file has been reached.
227 * @exception NullPointerException If <code>b</code> is <code>null</code>.
228 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
229 * <code>len</code> is negative, or <code>len</code> is greater than
230 * <code>b.length - off</code>
231 * @exception IOException if an I/O error occurs.
232 */
233 public int read(byte b[], int off, int len) throws IOException {
234 return readBytes(b, off, len);
235 }
236
237 /**
238 * Skips over and discards <code>n</code> bytes of data from the
239 * input stream.
240 *
241 * <p>The <code>skip</code> method may, for a variety of
242 * reasons, end up skipping over some smaller number of bytes,
243 * possibly <code>0</code>. If <code>n</code> is negative, the method
244 * will try to skip backwards. In case the backing file does not support
245 * backward skip at its current position, an <code>IOException</code> is
246 * thrown. The actual number of bytes skipped is returned. If it skips
247 * forwards, it returns a positive value. If it skips backwards, it
248 * returns a negative value.
249 *
250 * <p>This method may skip more bytes than what are remaining in the
251 * backing file. This produces no exception and the number of bytes skipped
252 * may include some number of bytes that were beyond the EOF of the
253 * backing file. Attempting to read from the stream after skipping past
254 * the end will result in -1 indicating the end of the file.
255 *
256 * @param n the number of bytes to be skipped.
257 * @return the actual number of bytes skipped.
258 * @exception IOException if n is negative, if the stream does not
259 * support seek, or if an I/O error occurs.
260 */
261 public native long skip(long n) throws IOException;
262
263 /**
264 * Returns an estimate of the number of remaining bytes that can be read (or
265 * skipped over) from this input stream without blocking by the next
266 * invocation of a method for this input stream. Returns 0 when the file
267 * position is beyond EOF. The next invocation might be the same thread
268 * or another thread. A single read or skip of this many bytes will not
269 * block, but may read or skip fewer bytes.
270 *
271 * <p> In some cases, a non-blocking read (or skip) may appear to be
272 * blocked when it is merely slow, for example when reading large
273 * files over slow networks.
274 *
275 * @return an estimate of the number of remaining bytes that can be read
276 * (or skipped over) from this input stream without blocking.
277 * @exception IOException if this file input stream has been closed by calling
278 * {@code close} or an I/O error occurs.
279 */
280 public native int available() throws IOException;
281
282 /**
283 * Closes this file input stream and releases any system resources
284 * associated with the stream.
285 *
286 * <p> If this stream has an associated channel then the channel is closed
287 * as well.
288 *
289 * @exception IOException if an I/O error occurs.
290 *
291 * @revised 1.4
292 * @spec JSR-51
293 */
294 public void close() throws IOException {
295 synchronized (closeLock) {
296 if (closed) {
297 return;
298 }
299 closed = true;
300 }
301 if (channel != null) {
302 channel.close();
303 }
304
305 fd.closeAll(new Closeable() {
306 public void close() throws IOException {
307 close0();
308 }
309 });
310 }
311
312 /**
313 * Returns the <code>FileDescriptor</code>
314 * object that represents the connection to
315 * the actual file in the file system being
316 * used by this <code>FileInputStream</code>.
317 *
318 * @return the file descriptor object associated with this stream.
319 * @exception IOException if an I/O error occurs.
320 * @see java.io.FileDescriptor
321 */
322 public final FileDescriptor getFD() throws IOException {
323 if (fd != null) {
324 return fd;
325 }
326 throw new IOException();
327 }
328
329 /**
330 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
331 * object associated with this file input stream.
332 *
333 * <p> The initial {@link java.nio.channels.FileChannel#position()
334 * position} of the returned channel will be equal to the
335 * number of bytes read from the file so far. Reading bytes from this
336 * stream will increment the channel's position. Changing the channel's
337 * position, either explicitly or by reading, will change this stream's
338 * file position.
339 *
340 * @return the file channel associated with this file input stream
341 *
342 * @since 1.4
343 * @spec JSR-51
344 */
345 public FileChannel getChannel() {
346 synchronized (this) {
347 if (channel == null) {
348 channel = FileChannelImpl.open(fd, true, false, this);
349 }
350 return channel;
351 }
352 }
353
354 private static native void initIDs();
355
356 private native void close0() throws IOException;
357
358 static {
359 initIDs();
360 }
361
362 /**
363 * Ensures that the <code>close</code> method of this file input stream is
364 * called when there are no more references to it.
365 *
366 * @exception IOException if an I/O error occurs.
367 * @see java.io.FileInputStream#close()
368 */
369 protected void finalize() throws IOException {
370 if ((fd != null) && (fd != FileDescriptor.in)) {
371 /* if fd is shared, the references in FileDescriptor
372 * will ensure that finalizer is only called when
373 * safe to do so. All references using the fd have
374 * become unreachable. We can call close()
375 */
376 close();
377 }
378 }
379 }