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    1   /*
    2    * Copyright (c) 1994, 2011, 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   }

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