1 /*
   2  * Copyright (c) 1994, 2019, 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} 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} is meant for reading streams of raw bytes
  38  * such as image data. For reading streams of characters, consider using
  39  * {@code FileReader}.
  40  *
  41  * @apiNote
  42  * To release resources used by this stream {@link #close} should be called
  43  * directly or by try-with-resources. Subclasses are responsible for the cleanup
  44  * of resources acquired by the subclass.
  45  * Subclasses that override {@link #finalize} in order to perform cleanup
  46  * should be modified to use alternative cleanup mechanisms such as
  47  * {@link java.lang.ref.Cleaner} and remove the overriding {@code finalize} method.
  48  *
  49  * @implSpec
  50  * If this FileInputStream has been subclassed and the {@link #close}
  51  * method has been overridden, the {@link #close} method will be
  52  * called when the FileInputStream is unreachable.
  53  * Otherwise, it is implementation specific how the resource cleanup described in
  54  * {@link #close} is performed.
  55 
  56  *
  57  * @author  Arthur van Hoff
  58  * @see     java.io.File
  59  * @see     java.io.FileDescriptor
  60  * @see     java.io.FileOutputStream
  61  * @see     java.nio.file.Files#newInputStream
  62  * @since   1.0
  63  */
  64 public class FileInputStream extends InputStream
  65 {
  66     /* File Descriptor - handle to the open file */
  67     private final FileDescriptor fd;
  68 
  69     /**
  70      * The path of the referenced file
  71      * (null if the stream is created with a file descriptor)
  72      */
  73     private final String path;
  74 
  75     private volatile FileChannel channel;
  76 
  77     private final Object closeLock = new Object();
  78 
  79     private volatile boolean closed;
  80 
  81     /**
  82      * Creates a {@code FileInputStream} by
  83      * opening a connection to an actual file,
  84      * the file named by the path name {@code name}
  85      * in the file system.  A new {@code FileDescriptor}
  86      * object is created to represent this file
  87      * connection.
  88      * <p>
  89      * First, if there is a security
  90      * manager, its {@code checkRead} method
  91      * is called with the {@code name} argument
  92      * as its argument.
  93      * <p>
  94      * If the named file does not exist, is a directory rather than a regular
  95      * file, or for some other reason cannot be opened for reading then a
  96      * {@code FileNotFoundException} is thrown.
  97      *
  98      * @param      name   the system-dependent file name.
  99      * @throws     FileNotFoundException  if the file does not exist,
 100      *             is a directory rather than a regular file,
 101      *             or for some other reason cannot be opened for
 102      *             reading.
 103      * @throws     SecurityException      if a security manager exists and its
 104      *             {@code checkRead} method denies read access
 105      *             to the file.
 106      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 107      */
 108     public FileInputStream(String name) throws FileNotFoundException {
 109         this(name != null ? new File(name) : null);
 110     }
 111 
 112     /**
 113      * Creates a {@code FileInputStream} by
 114      * opening a connection to an actual file,
 115      * the file named by the {@code File}
 116      * object {@code file} in the file system.
 117      * A new {@code FileDescriptor} object
 118      * is created to represent this file connection.
 119      * <p>
 120      * First, if there is a security manager,
 121      * its {@code checkRead} method  is called
 122      * with the path represented by the {@code file}
 123      * argument as its argument.
 124      * <p>
 125      * If the named file does not exist, is a directory rather than a regular
 126      * file, or for some other reason cannot be opened for reading then a
 127      * {@code FileNotFoundException} is thrown.
 128      *
 129      * @param      file   the file to be opened for reading.
 130      * @throws     FileNotFoundException  if the file does not exist,
 131      *             is a directory rather than a regular file,
 132      *             or for some other reason cannot be opened for
 133      *             reading.
 134      * @throws     SecurityException      if a security manager exists and its
 135      *             {@code checkRead} method denies read access to the file.
 136      * @see        java.io.File#getPath()
 137      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 138      */
 139     public FileInputStream(File file) throws FileNotFoundException {
 140         String name = (file != null ? file.getPath() : null);
 141         SecurityManager security = System.getSecurityManager();
 142         if (security != null) {
 143             security.checkRead(name);
 144         }
 145         if (name == null) {
 146             throw new NullPointerException();
 147         }
 148         if (file.isInvalid()) {
 149             throw new FileNotFoundException("Invalid file path");
 150         }
 151         fd = new FileDescriptor();
 152         fd.attach(this);
 153         path = name;
 154         open(name);
 155         FileCleanable.register(fd);       // open set the fd, register the cleanup
 156     }
 157 
 158     /**
 159      * Creates a {@code FileInputStream} by using the file descriptor
 160      * {@code fdObj}, which represents an existing connection to an
 161      * actual file in the file system.
 162      * <p>
 163      * If there is a security manager, its {@code checkRead} method is
 164      * called with the file descriptor {@code fdObj} as its argument to
 165      * see if it's ok to read the file descriptor. If read access is denied
 166      * to the file descriptor a {@code SecurityException} is thrown.
 167      * <p>
 168      * If {@code fdObj} is null then a {@code NullPointerException}
 169      * is thrown.
 170      * <p>
 171      * This constructor does not throw an exception if {@code fdObj}
 172      * is {@link java.io.FileDescriptor#valid() invalid}.
 173      * However, if the methods are invoked on the resulting stream to attempt
 174      * I/O on the stream, an {@code IOException} is thrown.
 175      *
 176      * @param      fdObj   the file descriptor to be opened for reading.
 177      * @throws     SecurityException      if a security manager exists and its
 178      *             {@code checkRead} method denies read access to the
 179      *             file descriptor.
 180      * @see        SecurityManager#checkRead(java.io.FileDescriptor)
 181      */
 182     public FileInputStream(FileDescriptor fdObj) {
 183         SecurityManager security = System.getSecurityManager();
 184         if (fdObj == null) {
 185             throw new NullPointerException();
 186         }
 187         if (security != null) {
 188             security.checkRead(fdObj);
 189         }
 190         fd = fdObj;
 191         path = null;
 192 
 193         /*
 194          * FileDescriptor is being shared by streams.
 195          * Register this stream with FileDescriptor tracker.
 196          */
 197         fd.attach(this);
 198     }
 199 
 200     /**
 201      * Opens the specified file for reading.
 202      * @param name the name of the file
 203      */
 204     private native void open0(String name) throws FileNotFoundException;
 205 
 206     // wrap native call to allow instrumentation
 207     /**
 208      * Opens the specified file for reading.
 209      * @param name the name of the file
 210      */
 211     private void open(String name) throws FileNotFoundException {
 212         open0(name);
 213     }
 214 
 215     /**
 216      * Reads a byte of data from this input stream. This method blocks
 217      * if no input is yet available.
 218      *
 219      * @return     the next byte of data, or {@code -1} if the end of the
 220      *             file is reached.
 221      * @throws     IOException  if an I/O error occurs.
 222      */
 223     public int read() throws IOException {
 224         return read0();
 225     }
 226 
 227     private native int read0() throws IOException;
 228 
 229     /**
 230      * Reads a subarray as a sequence of bytes.
 231      * @param     b the data to be written
 232      * @param     off the start offset in the data
 233      * @param     len the number of bytes that are written
 234      * @throws    IOException If an I/O error has occurred.
 235      */
 236     private native int readBytes(byte b[], int off, int len) throws IOException;
 237 
 238     /**
 239      * Reads up to {@code b.length} bytes of data from this input
 240      * stream into an array of bytes. This method blocks until some input
 241      * is available.
 242      *
 243      * @param      b   the buffer into which the data is read.
 244      * @return     the total number of bytes read into the buffer, or
 245      *             {@code -1} if there is no more data because the end of
 246      *             the file has been reached.
 247      * @throws     IOException  if an I/O error occurs.
 248      */
 249     public int read(byte b[]) throws IOException {
 250         return readBytes(b, 0, b.length);
 251     }
 252 
 253     /**
 254      * Reads up to {@code len} bytes of data from this input stream
 255      * into an array of bytes. If {@code len} is not zero, the method
 256      * blocks until some input is available; otherwise, no
 257      * bytes are read and {@code 0} is returned.
 258      *
 259      * @param      b     the buffer into which the data is read.
 260      * @param      off   the start offset in the destination array {@code b}
 261      * @param      len   the maximum number of bytes read.
 262      * @return     the total number of bytes read into the buffer, or
 263      *             {@code -1} if there is no more data because the end of
 264      *             the file has been reached.
 265      * @throws     NullPointerException If {@code b} is {@code null}.
 266      * @throws     IndexOutOfBoundsException If {@code off} is negative,
 267      *             {@code len} is negative, or {@code len} is greater than
 268      *             {@code b.length - off}
 269      * @throws     IOException  if an I/O error occurs.
 270      */
 271     public int read(byte b[], int off, int len) throws IOException {
 272         return readBytes(b, off, len);
 273     }
 274 
 275     /**
 276      * Skips over and discards {@code n} bytes of data from the
 277      * input stream.
 278      *
 279      * <p>The {@code skip} method may, for a variety of
 280      * reasons, end up skipping over some smaller number of bytes,
 281      * possibly {@code 0}. If {@code n} is negative, the method
 282      * will try to skip backwards. In case the backing file does not support
 283      * backward skip at its current position, an {@code IOException} is
 284      * thrown. The actual number of bytes skipped is returned. If it skips
 285      * forwards, it returns a positive value. If it skips backwards, it
 286      * returns a negative value.
 287      *
 288      * <p>This method may skip more bytes than what are remaining in the
 289      * backing file. This produces no exception and the number of bytes skipped
 290      * may include some number of bytes that were beyond the EOF of the
 291      * backing file. Attempting to read from the stream after skipping past
 292      * the end will result in -1 indicating the end of the file.
 293      *
 294      * @param      n   the number of bytes to be skipped.
 295      * @return     the actual number of bytes skipped.
 296      * @throws     IOException  if n is negative, if the stream does not
 297      *             support seek, or if an I/O error occurs.
 298      */
 299     public long skip(long n) throws IOException {
 300         return skip0(n);
 301     }
 302 
 303     private native long skip0(long n) throws IOException;
 304 
 305     /**
 306      * Returns an estimate of the number of remaining bytes that can be read (or
 307      * skipped over) from this input stream without blocking by the next
 308      * invocation of a method for this input stream. Returns 0 when the file
 309      * position is beyond EOF. The next invocation might be the same thread
 310      * or another thread. A single read or skip of this many bytes will not
 311      * block, but may read or skip fewer bytes.
 312      *
 313      * <p> In some cases, a non-blocking read (or skip) may appear to be
 314      * blocked when it is merely slow, for example when reading large
 315      * files over slow networks.
 316      *
 317      * @return     an estimate of the number of remaining bytes that can be read
 318      *             (or skipped over) from this input stream without blocking.
 319      * @throws     IOException  if this file input stream has been closed by calling
 320      *             {@code close} or an I/O error occurs.
 321      */
 322     public int available() throws IOException {
 323         return available0();
 324     }
 325 
 326     private native int available0() throws IOException;
 327 
 328     /**
 329      * Closes this file input stream and releases any system resources
 330      * associated with the stream.
 331      *
 332      * <p> If this stream has an associated channel then the channel is closed
 333      * as well.
 334      *
 335      * @apiNote
 336      * Overriding {@link #close} to perform cleanup actions is reliable
 337      * only when called directly or when called by try-with-resources.
 338      * Do not depend on finalization to invoke {@code close};
 339      * finalization is not reliable and is deprecated.
 340      * If cleanup of native resources is needed, other mechanisms such as
 341      * {@linkplain java.lang.ref.Cleaner} should be used.
 342      *
 343      * @throws     IOException  if an I/O error occurs.
 344      *
 345      * @revised 1.4
 346      * @spec JSR-51
 347      */
 348     public void close() throws IOException {
 349         if (closed) {
 350             return;
 351         }
 352         synchronized (closeLock) {
 353             if (closed) {
 354                 return;
 355             }
 356             closed = true;
 357         }
 358 
 359         FileChannel fc = channel;
 360         if (fc != null) {
 361             // possible race with getChannel(), benign since
 362             // FileChannel.close is final and idempotent
 363             fc.close();
 364         }
 365 
 366         fd.closeAll(new Closeable() {
 367             public void close() throws IOException {
 368                fd.close();
 369            }
 370         });
 371     }
 372 
 373     /**
 374      * Returns the {@code FileDescriptor}
 375      * object  that represents the connection to
 376      * the actual file in the file system being
 377      * used by this {@code FileInputStream}.
 378      *
 379      * @return     the file descriptor object associated with this stream.
 380      * @throws     IOException  if an I/O error occurs.
 381      * @see        java.io.FileDescriptor
 382      */
 383     public final FileDescriptor getFD() throws IOException {
 384         if (fd != null) {
 385             return fd;
 386         }
 387         throw new IOException();
 388     }
 389 
 390     /**
 391      * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
 392      * object associated with this file input stream.
 393      *
 394      * <p> The initial {@link java.nio.channels.FileChannel#position()
 395      * position} of the returned channel will be equal to the
 396      * number of bytes read from the file so far.  Reading bytes from this
 397      * stream will increment the channel's position.  Changing the channel's
 398      * position, either explicitly or by reading, will change this stream's
 399      * file position.
 400      *
 401      * @return  the file channel associated with this file input stream
 402      *
 403      * @since 1.4
 404      * @spec JSR-51
 405      */
 406     public FileChannel getChannel() {
 407         FileChannel fc = this.channel;
 408         if (fc == null) {
 409             synchronized (this) {
 410                 fc = this.channel;
 411                 if (fc == null) {
 412                     this.channel = fc = FileChannelImpl.open(fd, path, true,
 413                         false, false, this);
 414                     if (closed) {
 415                         try {
 416                             // possible race with close(), benign since
 417                             // FileChannel.close is final and idempotent
 418                             fc.close();
 419                         } catch (IOException ioe) {
 420                             throw new InternalError(ioe); // should not happen
 421                         }
 422                     }
 423                 }
 424             }
 425         }
 426         return fc;
 427     }
 428 
 429     private static native void initIDs();
 430 
 431     static {
 432         initIDs();
 433     }
 434 }