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     /**
  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.attach(this);
 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          * Register this stream with FileDescriptor tracker.
 168          */
 169         fd.attach(this);
 170     }
 171 
 172     /**
 173      * Opens the specified file for reading.
 174      * @param name the name of the file
 175      */
 176     private native void open(String name) throws FileNotFoundException;
 177 
 178     /**
 179      * Reads a byte of data from this input stream. This method blocks
 180      * if no input is yet available.
 181      *
 182      * @return     the next byte of data, or <code>-1</code> if the end of the
 183      *             file is reached.
 184      * @exception  IOException  if an I/O error occurs.
 185      */
 186     public native int read() throws IOException;
 187 
 188     /**
 189      * Reads a subarray as a sequence of bytes.
 190      * @param b the data to be written
 191      * @param off the start offset in the data
 192      * @param len the number of bytes that are written
 193      * @exception IOException If an I/O error has occurred.
 194      */
 195     private native int readBytes(byte b[], int off, int len) throws IOException;
 196 
 197     /**
 198      * Reads up to <code>b.length</code> bytes of data from this input
 199      * stream into an array of bytes. This method blocks until some input
 200      * is available.
 201      *
 202      * @param      b   the buffer into which the data is read.
 203      * @return     the total number of bytes read into the buffer, or
 204      *             <code>-1</code> if there is no more data because the end of
 205      *             the file has been reached.
 206      * @exception  IOException  if an I/O error occurs.
 207      */
 208     public int read(byte b[]) throws IOException {
 209         return readBytes(b, 0, b.length);
 210     }
 211 
 212     /**
 213      * Reads up to <code>len</code> bytes of data from this input stream
 214      * into an array of bytes. If <code>len</code> is not zero, the method
 215      * blocks until some input is available; otherwise, no
 216      * bytes are read and <code>0</code> is returned.
 217      *
 218      * @param      b     the buffer into which the data is read.
 219      * @param      off   the start offset in the destination array <code>b</code>
 220      * @param      len   the maximum number of bytes read.
 221      * @return     the total number of bytes read into the buffer, or
 222      *             <code>-1</code> if there is no more data because the end of
 223      *             the file has been reached.
 224      * @exception  NullPointerException If <code>b</code> is <code>null</code>.
 225      * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
 226      * <code>len</code> is negative, or <code>len</code> is greater than
 227      * <code>b.length - off</code>
 228      * @exception  IOException  if an I/O error occurs.
 229      */
 230     public int read(byte b[], int off, int len) throws IOException {
 231         return readBytes(b, off, len);
 232     }
 233 
 234     /**
 235      * Skips over and discards <code>n</code> bytes of data from the
 236      * input stream.
 237      *
 238      * <p>The <code>skip</code> method may, for a variety of
 239      * reasons, end up skipping over some smaller number of bytes,
 240      * possibly <code>0</code>. If <code>n</code> is negative, an
 241      * <code>IOException</code> is thrown, even though the <code>skip</code>
 242      * method of the {@link InputStream} superclass does nothing in this case.
 243      * The actual number of bytes skipped is returned.
 244      *
 245      * <p>This method may skip more bytes than are remaining in the backing
 246      * file. This produces no exception and the number of bytes skipped
 247      * may include some number of bytes that were beyond the EOF of the
 248      * backing file. Attempting to read from the stream after skipping past
 249      * the end will result in -1 indicating the end of the file.
 250      *
 251      * @param      n   the number of bytes to be skipped.
 252      * @return     the actual number of bytes skipped.
 253      * @exception  IOException  if n is negative, if the stream does not
 254      *             support seek, or if an I/O error occurs.
 255      */
 256     public native long skip(long n) throws IOException;
 257 
 258     /**
 259      * Returns an estimate of the number of remaining bytes that can be read (or
 260      * skipped over) from this input stream without blocking by the next
 261      * invocation of a method for this input stream. The next invocation might be
 262      * the same thread or another thread.  A single read or skip of this
 263      * many bytes will not block, but may read or skip fewer bytes.
 264      *
 265      * <p> In some cases, a non-blocking read (or skip) may appear to be
 266      * blocked when it is merely slow, for example when reading large
 267      * files over slow networks.
 268      *
 269      * @return     an estimate of the number of remaining bytes that can be read
 270      *             (or skipped over) from this input stream without blocking.
 271      * @exception  IOException  if this file input stream has been closed by calling
 272      *             {@code close} or an I/O error occurs.
 273      */
 274     public native int available() throws IOException;
 275 
 276     /**
 277      * Closes this file input stream and releases any system resources
 278      * associated with the stream.
 279      *
 280      * <p> If this stream has an associated channel then the channel is closed
 281      * as well.
 282      *
 283      * @exception  IOException  if an I/O error occurs.
 284      *
 285      * @revised 1.4
 286      * @spec JSR-51
 287      */
 288     public void close() throws IOException {
 289         synchronized (closeLock) {
 290             if (closed) {
 291                 return;
 292             }
 293             closed = true;
 294         }
 295         if (channel != null) {
 296            channel.close();
 297         }
 298         fd.closeAll(new Closeable() {
 299             public void close() throws IOException {
 300                close0();
 301            }
 302         });
 303     }
 304 
 305     /**
 306      * Returns the <code>FileDescriptor</code>
 307      * object  that represents the connection to
 308      * the actual file in the file system being
 309      * used by this <code>FileInputStream</code>.
 310      *
 311      * @return     the file descriptor object associated with this stream.
 312      * @exception  IOException  if an I/O error occurs.
 313      * @see        java.io.FileDescriptor
 314      */
 315     public final FileDescriptor getFD() throws IOException {
 316         if (fd != null) {
 317             return fd;
 318         }
 319         throw new IOException();
 320     }
 321 
 322     /**
 323      * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
 324      * object associated with this file input stream.
 325      *
 326      * <p> The initial {@link java.nio.channels.FileChannel#position()
 327      * </code>position<code>} of the returned channel will be equal to the
 328      * number of bytes read from the file so far.  Reading bytes from this
 329      * stream will increment the channel's position.  Changing the channel's
 330      * position, either explicitly or by reading, will change this stream's
 331      * file position.
 332      *
 333      * @return  the file channel associated with this file input stream
 334      *
 335      * @since 1.4
 336      * @spec JSR-51
 337      */
 338     public FileChannel getChannel() {
 339         synchronized (this) {
 340             if (channel == null) {
 341                 channel = FileChannelImpl.open(fd, true, false, this);
 342             }
 343             return channel;
 344         }
 345     }
 346 
 347     private static native void initIDs();
 348 
 349     private native void close0() throws IOException;
 350 
 351     static {
 352         initIDs();
 353     }
 354 
 355     /**
 356      * Ensures that the <code>close</code> method of this file input stream is
 357      * called when there are no more references to it.
 358      *
 359      * @exception  IOException  if an I/O error occurs.
 360      * @see        java.io.FileInputStream#close()
 361      */
 362     protected void finalize() throws IOException {
 363         if ((fd != null) &&  (fd != FileDescriptor.in)) {
 364             /* if fd is shared, the references in FileDescriptor
 365              * will ensure that finalizer is only called when
 366              * safe to do so. All references using the fd have
 367              * become unreachable. We can call close()
 368              */
 369             close();
 370         }
 371     }
 372 }