1/*
2 * Copyright (c) 1994, 2017, 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
26package java.io;
27
28import java.nio.channels.FileChannel;
29import 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   1.0
47 */
48public
49class 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 volatile FileChannel channel;
61
62    private final Object closeLock = new Object();
63
64    private volatile boolean closed;
65
66    /**
67     * Creates a <code>FileInputStream</code> by
68     * opening a connection to an actual file,
69     * the file named by the path name <code>name</code>
70     * in the file system.  A new <code>FileDescriptor</code>
71     * object is created to represent this file
72     * connection.
73     * <p>
74     * First, if there is a security
75     * manager, its <code>checkRead</code> method
76     * is called with the <code>name</code> argument
77     * as its argument.
78     * <p>
79     * If the named file does not exist, is a directory rather than a regular
80     * file, or for some other reason cannot be opened for reading then a
81     * <code>FileNotFoundException</code> is thrown.
82     *
83     * @param      name   the system-dependent file name.
84     * @exception  FileNotFoundException  if the file does not exist,
85     *                   is a directory rather than a regular file,
86     *                   or for some other reason cannot be opened for
87     *                   reading.
88     * @exception  SecurityException      if a security manager exists and its
89     *               <code>checkRead</code> method denies read access
90     *               to the file.
91     * @see        java.lang.SecurityManager#checkRead(java.lang.String)
92     */
93    public FileInputStream(String name) throws FileNotFoundException {
94        this(name != null ? new File(name) : null);
95    }
96
97    /**
98     * Creates a <code>FileInputStream</code> by
99     * opening a connection to an actual file,
100     * the file named by the <code>File</code>
101     * object <code>file</code> in the file system.
102     * A new <code>FileDescriptor</code> object
103     * is created to represent this file connection.
104     * <p>
105     * First, if there is a security manager,
106     * its <code>checkRead</code> method  is called
107     * with the path represented by the <code>file</code>
108     * argument as its argument.
109     * <p>
110     * If the named file does not exist, is a directory rather than a regular
111     * file, or for some other reason cannot be opened for reading then a
112     * <code>FileNotFoundException</code> is thrown.
113     *
114     * @param      file   the file to be opened for reading.
115     * @exception  FileNotFoundException  if the file does not exist,
116     *                   is a directory rather than a regular file,
117     *                   or for some other reason cannot be opened for
118     *                   reading.
119     * @exception  SecurityException      if a security manager exists and its
120     *               <code>checkRead</code> method denies read access to the file.
121     * @see        java.io.File#getPath()
122     * @see        java.lang.SecurityManager#checkRead(java.lang.String)
123     */
124    public FileInputStream(File file) throws FileNotFoundException {
125        String name = (file != null ? file.getPath() : null);
126        SecurityManager security = System.getSecurityManager();
127        if (security != null) {
128            security.checkRead(name);
129        }
130        if (name == null) {
131            throw new NullPointerException();
132        }
133        if (file.isInvalid()) {
134            throw new FileNotFoundException("Invalid file path");
135        }
136        fd = new FileDescriptor();
137        fd.attach(this);
138        path = name;
139        open(name);
140    }
141
142    /**
143     * Creates a <code>FileInputStream</code> by using the file descriptor
144     * <code>fdObj</code>, which represents an existing connection to an
145     * actual file in the file system.
146     * <p>
147     * If there is a security manager, its <code>checkRead</code> method is
148     * called with the file descriptor <code>fdObj</code> as its argument to
149     * see if it's ok to read the file descriptor. If read access is denied
150     * to the file descriptor a <code>SecurityException</code> is thrown.
151     * <p>
152     * If <code>fdObj</code> is null then a <code>NullPointerException</code>
153     * is thrown.
154     * <p>
155     * This constructor does not throw an exception if <code>fdObj</code>
156     * is {@link java.io.FileDescriptor#valid() invalid}.
157     * However, if the methods are invoked on the resulting stream to attempt
158     * I/O on the stream, an <code>IOException</code> is thrown.
159     *
160     * @param      fdObj   the file descriptor to be opened for reading.
161     * @throws     SecurityException      if a security manager exists and its
162     *                 <code>checkRead</code> method denies read access to the
163     *                 file descriptor.
164     * @see        SecurityManager#checkRead(java.io.FileDescriptor)
165     */
166    public FileInputStream(FileDescriptor fdObj) {
167        SecurityManager security = System.getSecurityManager();
168        if (fdObj == null) {
169            throw new NullPointerException();
170        }
171        if (security != null) {
172            security.checkRead(fdObj);
173        }
174        fd = fdObj;
175        path = null;
176
177        /*
178         * FileDescriptor is being shared by streams.
179         * Register this stream with FileDescriptor tracker.
180         */
181        fd.attach(this);
182    }
183
184    /**
185     * Opens the specified file for reading.
186     * @param name the name of the file
187     */
188    private native void open0(String name) throws FileNotFoundException;
189
190    // wrap native call to allow instrumentation
191    /**
192     * Opens the specified file for reading.
193     * @param name the name of the file
194     */
195    private void open(String name) throws FileNotFoundException {
196        open0(name);
197    }
198
199    /**
200     * Reads a byte of data from this input stream. This method blocks
201     * if no input is yet available.
202     *
203     * @return     the next byte of data, or <code>-1</code> if the end of the
204     *             file is reached.
205     * @exception  IOException  if an I/O error occurs.
206     */
207    public int read() throws IOException {
208        return read0();
209    }
210
211    private native int read0() throws IOException;
212
213    /**
214     * Reads a subarray as a sequence of bytes.
215     * @param b the data to be written
216     * @param off the start offset in the data
217     * @param len the number of bytes that are written
218     * @exception IOException If an I/O error has occurred.
219     */
220    private native int readBytes(byte b[], int off, int len) throws IOException;
221
222    /**
223     * Reads up to <code>b.length</code> bytes of data from this input
224     * stream into an array of bytes. This method blocks until some input
225     * is available.
226     *
227     * @param      b   the buffer into which the data is read.
228     * @return     the total number of bytes read into the buffer, or
229     *             <code>-1</code> if there is no more data because the end of
230     *             the file has been reached.
231     * @exception  IOException  if an I/O error occurs.
232     */
233    public int read(byte b[]) throws IOException {
234        return readBytes(b, 0, b.length);
235    }
236
237    /**
238     * Reads up to <code>len</code> bytes of data from this input stream
239     * into an array of bytes. If <code>len</code> is not zero, the method
240     * blocks until some input is available; otherwise, no
241     * bytes are read and <code>0</code> is returned.
242     *
243     * @param      b     the buffer into which the data is read.
244     * @param      off   the start offset in the destination array <code>b</code>
245     * @param      len   the maximum number of bytes read.
246     * @return     the total number of bytes read into the buffer, or
247     *             <code>-1</code> if there is no more data because the end of
248     *             the file has been reached.
249     * @exception  NullPointerException If <code>b</code> is <code>null</code>.
250     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
251     * <code>len</code> is negative, or <code>len</code> is greater than
252     * <code>b.length - off</code>
253     * @exception  IOException  if an I/O error occurs.
254     */
255    public int read(byte b[], int off, int len) throws IOException {
256        return readBytes(b, off, len);
257    }
258
259    /**
260     * Skips over and discards <code>n</code> bytes of data from the
261     * input stream.
262     *
263     * <p>The <code>skip</code> method may, for a variety of
264     * reasons, end up skipping over some smaller number of bytes,
265     * possibly <code>0</code>. If <code>n</code> is negative, the method
266     * will try to skip backwards. In case the backing file does not support
267     * backward skip at its current position, an <code>IOException</code> is
268     * thrown. The actual number of bytes skipped is returned. If it skips
269     * forwards, it returns a positive value. If it skips backwards, it
270     * returns a negative value.
271     *
272     * <p>This method may skip more bytes than what are remaining in the
273     * backing file. This produces no exception and the number of bytes skipped
274     * may include some number of bytes that were beyond the EOF of the
275     * backing file. Attempting to read from the stream after skipping past
276     * the end will result in -1 indicating the end of the file.
277     *
278     * @param      n   the number of bytes to be skipped.
279     * @return     the actual number of bytes skipped.
280     * @exception  IOException  if n is negative, if the stream does not
281     *             support seek, or if an I/O error occurs.
282     */
283    public long skip(long n) throws IOException {
284        return skip0(n);
285    }
286
287    private native long skip0(long n) throws IOException;
288
289    /**
290     * Returns an estimate of the number of remaining bytes that can be read (or
291     * skipped over) from this input stream without blocking by the next
292     * invocation of a method for this input stream. Returns 0 when the file
293     * position is beyond EOF. The next invocation might be the same thread
294     * or another thread. A single read or skip of this many bytes will not
295     * block, but may read or skip fewer bytes.
296     *
297     * <p> In some cases, a non-blocking read (or skip) may appear to be
298     * blocked when it is merely slow, for example when reading large
299     * files over slow networks.
300     *
301     * @return     an estimate of the number of remaining bytes that can be read
302     *             (or skipped over) from this input stream without blocking.
303     * @exception  IOException  if this file input stream has been closed by calling
304     *             {@code close} or an I/O error occurs.
305     */
306    public int available() throws IOException {
307        return available0();
308    }
309
310    private native int available0() throws IOException;
311
312    /**
313     * Closes this file input stream and releases any system resources
314     * associated with the stream.
315     *
316     * <p> If this stream has an associated channel then the channel is closed
317     * as well.
318     *
319     * @exception  IOException  if an I/O error occurs.
320     *
321     * @revised 1.4
322     * @spec JSR-51
323     */
324    public void close() throws IOException {
325        if (closed) {
326            return;
327        }
328        synchronized (closeLock) {
329            if (closed) {
330                return;
331            }
332            closed = true;
333        }
334
335        FileChannel fc = channel;
336        if (fc != null) {
337            // possible race with getChannel(), benign since
338            // FileChannel.close is final and idempotent
339            fc.close();
340        }
341
342        fd.closeAll(new Closeable() {
343            public void close() throws IOException {
344               close0();
345           }
346        });
347    }
348
349    /**
350     * Returns the <code>FileDescriptor</code>
351     * object  that represents the connection to
352     * the actual file in the file system being
353     * used by this <code>FileInputStream</code>.
354     *
355     * @return     the file descriptor object associated with this stream.
356     * @exception  IOException  if an I/O error occurs.
357     * @see        java.io.FileDescriptor
358     */
359    public final FileDescriptor getFD() throws IOException {
360        if (fd != null) {
361            return fd;
362        }
363        throw new IOException();
364    }
365
366    /**
367     * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
368     * object associated with this file input stream.
369     *
370     * <p> The initial {@link java.nio.channels.FileChannel#position()
371     * position} of the returned channel will be equal to the
372     * number of bytes read from the file so far.  Reading bytes from this
373     * stream will increment the channel's position.  Changing the channel's
374     * position, either explicitly or by reading, will change this stream's
375     * file position.
376     *
377     * @return  the file channel associated with this file input stream
378     *
379     * @since 1.4
380     * @spec JSR-51
381     */
382    public FileChannel getChannel() {
383        FileChannel fc = this.channel;
384        if (fc == null) {
385            synchronized (this) {
386                fc = this.channel;
387                if (fc == null) {
388                    this.channel = fc = FileChannelImpl.open(fd, path, true, false, this);
389                    if (closed) {
390                        try {
391                            // possible race with close(), benign since
392                            // FileChannel.close is final and idempotent
393                            fc.close();
394                        } catch (IOException ioe) {
395                            throw new InternalError(ioe); // should not happen
396                        }
397                    }
398                }
399            }
400        }
401        return fc;
402    }
403
404    private static native void initIDs();
405
406    private native void close0() throws IOException;
407
408    static {
409        initIDs();
410    }
411
412    /**
413     * Ensures that the <code>close</code> method of this file input stream is
414     * called when there are no more references to it.
415     *
416     * @deprecated The {@code finalize} method has been deprecated.
417     *     Subclasses that override {@code finalize} in order to perform cleanup
418     *     should be modified to use alternative cleanup mechanisms and
419     *     to remove the overriding {@code finalize} method.
420     *     When overriding the {@code finalize} method, its implementation must explicitly
421     *     ensure that {@code super.finalize()} is invoked as described in {@link Object#finalize}.
422     *     See the specification for {@link Object#finalize()} for further
423     *     information about migration options.
424     *
425     * @exception  IOException  if an I/O error occurs.
426     * @see        java.io.FileInputStream#close()
427     */
428    @Deprecated(since="9")
429    protected void finalize() throws IOException {
430        if ((fd != null) &&  (fd != FileDescriptor.in)) {
431            /* if fd is shared, the references in FileDescriptor
432             * will ensure that finalizer is only called when
433             * safe to do so. All references using the fd have
434             * become unreachable. We can call close()
435             */
436            close();
437        }
438    }
439}
440