1 /*
   2  * Copyright (c) 1994, 2012, 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     private static final ThreadLocal<Boolean> runningFinalize =
  60         new ThreadLocal<>();
  61 
  62     private static boolean isRunningFinalize() {
  63         Boolean val;
  64         if ((val = runningFinalize.get()) != null)
  65             return val.booleanValue();
  66         return false;
  67     }
  68 
  69     /**
  70      * Creates a <code>FileInputStream</code> by
  71      * opening a connection to an actual file,
  72      * the file named by the path name <code>name</code>
  73      * in the file system.  A new <code>FileDescriptor</code>
  74      * object is created to represent this file
  75      * connection.
  76      * <p>
  77      * First, if there is a security
  78      * manager, its <code>checkRead</code> method
  79      * is called with the <code>name</code> argument
  80      * as its argument.
  81      * <p>
  82      * If the named file does not exist, is a directory rather than a regular
  83      * file, or for some other reason cannot be opened for reading then a
  84      * <code>FileNotFoundException</code> is thrown.
  85      *
  86      * @param      name   the system-dependent file name.
  87      * @exception  FileNotFoundException  if the file does not exist,
  88      *                   is a directory rather than a regular file,
  89      *                   or for some other reason cannot be opened for
  90      *                   reading.
  91      * @exception  SecurityException      if a security manager exists and its
  92      *               <code>checkRead</code> method denies read access
  93      *               to the file.
  94      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
  95      */
  96     public FileInputStream(String name) throws FileNotFoundException {
  97         this(name != null ? new File(name) : null);
  98     }
  99 
 100     /**
 101      * Creates a <code>FileInputStream</code> by
 102      * opening a connection to an actual file,
 103      * the file named by the <code>File</code>
 104      * object <code>file</code> in the file system.
 105      * A new <code>FileDescriptor</code> object
 106      * is created to represent this file connection.
 107      * <p>
 108      * First, if there is a security manager,
 109      * its <code>checkRead</code> method  is called
 110      * with the path represented by the <code>file</code>
 111      * argument as its argument.
 112      * <p>
 113      * If the named file does not exist, is a directory rather than a regular
 114      * file, or for some other reason cannot be opened for reading then a
 115      * <code>FileNotFoundException</code> is thrown.
 116      *
 117      * @param      file   the file to be opened for reading.
 118      * @exception  FileNotFoundException  if the file does not exist,
 119      *                   is a directory rather than a regular file,
 120      *                   or for some other reason cannot be opened for
 121      *                   reading.
 122      * @exception  SecurityException      if a security manager exists and its
 123      *               <code>checkRead</code> method denies read access to the file.
 124      * @see        java.io.File#getPath()
 125      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 126      */
 127     public FileInputStream(File file) throws FileNotFoundException {
 128         String name = (file != null ? file.getPath() : null);
 129         SecurityManager security = System.getSecurityManager();
 130         if (security != null) {
 131             security.checkRead(name);
 132         }
 133         if (name == null) {
 134             throw new NullPointerException();
 135         }
 136         fd = new FileDescriptor();
 137         fd.incrementAndGetUseCount();
 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 
 175         /*
 176          * FileDescriptor is being shared by streams.
 177          * Ensure that it's GC'ed only when all the streams/channels are done
 178          * using it.
 179          */
 180         fd.incrementAndGetUseCount();
 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, an
 252      * <code>IOException</code> is thrown, even though the <code>skip</code>
 253      * method of the {@link InputStream} superclass does nothing in this case.
 254      * The actual number of bytes skipped is returned.
 255      *
 256      * <p>This method may skip more bytes than are remaining in the backing
 257      * file. This produces no exception and the number of bytes skipped
 258      * may include some number of bytes that were beyond the EOF of the
 259      * backing file. Attempting to read from the stream after skipping past
 260      * the end will result in -1 indicating the end of the file.
 261      *
 262      * @param      n   the number of bytes to be skipped.
 263      * @return     the actual number of bytes skipped.
 264      * @exception  IOException  if n is negative, if the stream does not
 265      *             support seek, or if an I/O error occurs.
 266      */
 267     public native long skip(long n) throws IOException;
 268 
 269     /**
 270      * Returns an estimate of the number of remaining bytes that can be read (or
 271      * skipped over) from this input stream without blocking by the next
 272      * invocation of a method for this input stream. The next invocation might be
 273      * the same thread or another thread.  A single read or skip of this
 274      * many bytes will not block, but may read or skip fewer bytes.
 275      *
 276      * <p> In some cases, a non-blocking read (or skip) may appear to be
 277      * blocked when it is merely slow, for example when reading large
 278      * files over slow networks.
 279      *
 280      * @return     an estimate of the number of remaining bytes that can be read
 281      *             (or skipped over) from this input stream without blocking.
 282      * @exception  IOException  if this file input stream has been closed by calling
 283      *             {@code close} or an I/O error occurs.
 284      */
 285     public native int available() throws IOException;
 286 
 287     /**
 288      * Closes this file input stream and releases any system resources
 289      * associated with the stream.
 290      *
 291      * <p> If this stream has an associated channel then the channel is closed
 292      * as well.
 293      *
 294      * @exception  IOException  if an I/O error occurs.
 295      *
 296      * @revised 1.4
 297      * @spec JSR-51
 298      */
 299     public void close() throws IOException {
 300         synchronized (closeLock) {
 301             if (closed) {
 302                 return;
 303             }
 304             closed = true;
 305         }
 306         if (channel != null) {
 307             /*
 308              * Decrement the FD use count associated with the channel
 309              * The use count is incremented whenever a new channel
 310              * is obtained from this stream.
 311              */
 312            fd.decrementAndGetUseCount();
 313            channel.close();
 314         }
 315 
 316         /*
 317          * Decrement the FD use count associated with this stream
 318          */
 319         int useCount = fd.decrementAndGetUseCount();
 320 
 321         /*
 322          * If FileDescriptor is still in use by another stream, the finalizer
 323          * will not close it.
 324          */
 325         if ((useCount <= 0) || !isRunningFinalize()) {
 326             close0();
 327         }
 328     }
 329 
 330     /**
 331      * Returns the <code>FileDescriptor</code>
 332      * object  that represents the connection to
 333      * the actual file in the file system being
 334      * used by this <code>FileInputStream</code>.
 335      *
 336      * @return     the file descriptor object associated with this stream.
 337      * @exception  IOException  if an I/O error occurs.
 338      * @see        java.io.FileDescriptor
 339      */
 340     public final FileDescriptor getFD() throws IOException {
 341         if (fd != null) return fd;
 342         throw new IOException();
 343     }
 344 
 345     /**
 346      * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
 347      * object associated with this file input stream.
 348      *
 349      * <p> The initial {@link java.nio.channels.FileChannel#position()
 350      * </code>position<code>} of the returned channel will be equal to the
 351      * number of bytes read from the file so far.  Reading bytes from this
 352      * stream will increment the channel's position.  Changing the channel's
 353      * position, either explicitly or by reading, will change this stream's
 354      * file position.
 355      *
 356      * @return  the file channel associated with this file input stream
 357      *
 358      * @since 1.4
 359      * @spec JSR-51
 360      */
 361     public FileChannel getChannel() {
 362         synchronized (this) {
 363             if (channel == null) {
 364                 channel = FileChannelImpl.open(fd, true, false, this);
 365 
 366                 /*
 367                  * Increment fd's use count. Invoking the channel's close()
 368                  * method will result in decrementing the use count set for
 369                  * the channel.
 370                  */
 371                 fd.incrementAndGetUseCount();
 372             }
 373             return channel;
 374         }
 375     }
 376 
 377     private static native void initIDs();
 378 
 379     private native void close0() throws IOException;
 380 
 381     static {
 382         initIDs();
 383     }
 384 
 385     /**
 386      * Ensures that the <code>close</code> method of this file input stream is
 387      * called when there are no more references to it.
 388      *
 389      * @exception  IOException  if an I/O error occurs.
 390      * @see        java.io.FileInputStream#close()
 391      */
 392     protected void finalize() throws IOException {
 393         if ((fd != null) &&  (fd != FileDescriptor.in)) {
 394 
 395             /*
 396              * Finalizer should not release the FileDescriptor if another
 397              * stream is still using it. If the user directly invokes
 398              * close() then the FileDescriptor is also released.
 399              */
 400             runningFinalize.set(Boolean.TRUE);
 401             try {
 402                 close();
 403             } finally {
 404                 runningFinalize.set(Boolean.FALSE);
 405             }
 406         }
 407     }
 408 }