/*

  * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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  */

 package java.io;

 import java.nio.channels.FileChannel;

 import sun.nio.ch.FileChannelImpl;

 /**

  * A <code>FileInputStream</code> obtains input bytes

  * from a file in a file system. What files

  * are  available depends on the host environment.

  *

  * <p><code>FileInputStream</code> is meant for reading streams of raw bytes

  * such as image data. For reading streams of characters, consider using

  * <code>FileReader</code>.

  *

  * @author  Arthur van Hoff

  * @see     java.io.File

  * @see     java.io.FileDescriptor

  * @see     java.io.FileOutputStream

  * @see     java.nio.file.Files#newInputStream

  * @since   JDK1.0

  */

 public

 class FileInputStream extends InputStream

 {

     /* File Descriptor - handle to the open file */

     private final FileDescriptor fd;

     private FileChannel channel = null;

     private final Object closeLock = new Object();

     private volatile boolean closed = false;

     private static final ThreadLocal<Boolean> runningFinalize =

         new ThreadLocal<>();

     private static boolean isRunningFinalize() {

         Boolean val;

         if ((val = runningFinalize.get()) != null)

             return val.booleanValue();

         return false;

     }

     /**

      * Creates a <code>FileInputStream</code> by

      * opening a connection to an actual file,

      * the file named by the path name <code>name</code>

      * in the file system.  A new <code>FileDescriptor</code>

      * object is created to represent this file

      * connection.

      * <p>

      * First, if there is a security

      * manager, its <code>checkRead</code> method

      * is called with the <code>name</code> argument

      * as its argument.

      * <p>

      * If the named file does not exist, is a directory rather than a regular

      * file, or for some other reason cannot be opened for reading then a

      * <code>FileNotFoundException</code> is thrown.

      *

      * @param      name   the system-dependent file name.

      * @exception  FileNotFoundException  if the file does not exist,

      *                   is a directory rather than a regular file,

      *                   or for some other reason cannot be opened for

      *                   reading.

      * @exception  SecurityException      if a security manager exists and its

      *               <code>checkRead</code> method denies read access

      *               to the file.

      * @see        java.lang.SecurityManager#checkRead(java.lang.String)

      */

     public FileInputStream(String name) throws FileNotFoundException {

         this(name != null ? new File(name) : null);

     }

     /**

      * Creates a <code>FileInputStream</code> by

      * opening a connection to an actual file,

      * the file named by the <code>File</code>

      * object <code>file</code> in the file system.

      * A new <code>FileDescriptor</code> object

      * is created to represent this file connection.

      * <p>

      * First, if there is a security manager,

      * its <code>checkRead</code> method  is called

      * with the path represented by the <code>file</code>

      * argument as its argument.

      * <p>

      * If the named file does not exist, is a directory rather than a regular

      * file, or for some other reason cannot be opened for reading then a

      * <code>FileNotFoundException</code> is thrown.

      *

      * @param      file   the file to be opened for reading.

      * @exception  FileNotFoundException  if the file does not exist,

      *                   is a directory rather than a regular file,

      *                   or for some other reason cannot be opened for

      *                   reading.

      * @exception  SecurityException      if a security manager exists and its

      *               <code>checkRead</code> method denies read access to the file.

      * @see        java.io.File#getPath()

      * @see        java.lang.SecurityManager#checkRead(java.lang.String)

      */

     public FileInputStream(File file) throws FileNotFoundException {

         String name = (file != null ? file.getPath() : null);

         SecurityManager security = System.getSecurityManager();

         if (security != null) {

             security.checkRead(name);

         }

         if (name == null) {

             throw new NullPointerException();

         }

         fd = new FileDescriptor();

         fd.incrementAndGetUseCount();

         open(name);

     }

     /**

      * Creates a <code>FileInputStream</code> by using the file descriptor

      * <code>fdObj</code>, which represents an existing connection to an

      * actual file in the file system.

      * <p>

      * If there is a security manager, its <code>checkRead</code> method is

      * called with the file descriptor <code>fdObj</code> as its argument to

      * see if it's ok to read the file descriptor. If read access is denied

      * to the file descriptor a <code>SecurityException</code> is thrown.

      * <p>

      * If <code>fdObj</code> is null then a <code>NullPointerException</code>

      * is thrown.

      * <p>

      * This constructor does not throw an exception if <code>fdObj</code>

      * is {@link java.io.FileDescriptor#valid() invalid}.

      * However, if the methods are invoked on the resulting stream to attempt

      * I/O on the stream, an <code>IOException</code> is thrown.

      *

      * @param      fdObj   the file descriptor to be opened for reading.

      * @throws     SecurityException      if a security manager exists and its

      *                 <code>checkRead</code> method denies read access to the

      *                 file descriptor.

      * @see        SecurityManager#checkRead(java.io.FileDescriptor)

      */

     public FileInputStream(FileDescriptor fdObj) {

         SecurityManager security = System.getSecurityManager();

         if (fdObj == null) {

             throw new NullPointerException();

         }

         if (security != null) {

             security.checkRead(fdObj);

         }

         fd = fdObj;

         /*

          * FileDescriptor is being shared by streams.

          * Ensure that it's GC'ed only when all the streams/channels are done

          * using it.

          */

         fd.incrementAndGetUseCount();

     }

     /**

      * Opens the specified file for reading.

      * @param name the name of the file

      */

     private native void open(String name) throws FileNotFoundException;

     /**

      * Reads a byte of data from this input stream. This method blocks

      * if no input is yet available.

      *

      * @return     the next byte of data, or <code>-1</code> if the end of the

      *             file is reached.

      * @exception  IOException  if an I/O error occurs.

      */

     public native int read() throws IOException;

     /**

      * Reads a subarray as a sequence of bytes.

      * @param b the data to be written

      * @param off the start offset in the data

      * @param len the number of bytes that are written

      * @exception IOException If an I/O error has occurred.

      */

     private native int readBytes(byte b[], int off, int len) throws IOException;

     /**

      * Reads up to <code>b.length</code> bytes of data from this input

      * stream into an array of bytes. This method blocks until some input

      * is available.

      *

      * @param      b   the buffer into which the data is read.

      * @return     the total number of bytes read into the buffer, or

      *             <code>-1</code> if there is no more data because the end of

      *             the file has been reached.

      * @exception  IOException  if an I/O error occurs.

      */

     public int read(byte b[]) throws IOException {

         return readBytes(b, 0, b.length);

     }

     /**

      * Reads up to <code>len</code> bytes of data from this input stream

      * into an array of bytes. If <code>len</code> is not zero, the method

      * blocks until some input is available; otherwise, no

      * bytes are read and <code>0</code> is returned.

      *

      * @param      b     the buffer into which the data is read.

      * @param      off   the start offset in the destination array <code>b</code>

      * @param      len   the maximum number of bytes read.

      * @return     the total number of bytes read into the buffer, or

      *             <code>-1</code> if there is no more data because the end of

      *             the file has been reached.

      * @exception  NullPointerException If <code>b</code> is <code>null</code>.

      * @exception  IndexOutOfBoundsException If <code>off</code> is negative,

      * <code>len</code> is negative, or <code>len</code> is greater than

      * <code>b.length - off</code>

      * @exception  IOException  if an I/O error occurs.

      */

     public int read(byte b[], int off, int len) throws IOException {

         return readBytes(b, off, len);

     }

     /**

      * Skips over and discards <code>n</code> bytes of data from the

      * input stream.

      *

      * <p>The <code>skip</code> method may, for a variety of

      * reasons, end up skipping over some smaller number of bytes,

      * possibly <code>0</code>. If <code>n</code> is negative, an

      * <code>IOException</code> is thrown, even though the <code>skip</code>

      * method of the {@link InputStream} superclass does nothing in this case.

      * The actual number of bytes skipped is returned.

      *

      * <p>This method may skip more bytes than are remaining in the backing

      * file. This produces no exception and the number of bytes skipped

      * may include some number of bytes that were beyond the EOF of the

      * backing file. Attempting to read from the stream after skipping past

      * the end will result in -1 indicating the end of the file.

      *

      * @param      n   the number of bytes to be skipped.

      * @return     the actual number of bytes skipped.

      * @exception  IOException  if n is negative, if the stream does not

      *             support seek, or if an I/O error occurs.

      */

     public native long skip(long n) throws IOException;

     /**

      * Returns an estimate of the number of remaining bytes that can be read (or

      * skipped over) from this input stream without blocking by the next

      * invocation of a method for this input stream. The next invocation might be

      * the same thread or another thread.  A single read or skip of this

      * many bytes will not block, but may read or skip fewer bytes.

      *

      * <p> In some cases, a non-blocking read (or skip) may appear to be

      * blocked when it is merely slow, for example when reading large

      * files over slow networks.

      *

      * @return     an estimate of the number of remaining bytes that can be read

      *             (or skipped over) from this input stream without blocking.

      * @exception  IOException  if this file input stream has been closed by calling

      *             {@code close} or an I/O error occurs.

      */

     public native int available() throws IOException;

     /**

      * Closes this file input stream and releases any system resources

      * associated with the stream.

      *

      * <p> If this stream has an associated channel then the channel is closed

      * as well.

      *

      * @exception  IOException  if an I/O error occurs.

      *

      * @revised 1.4

      * @spec JSR-51

      */

     public void close() throws IOException {

         synchronized (closeLock) {

             if (closed) {

                 return;

             }

             closed = true;

         }

         if (channel != null) {

             /*

              * Decrement the FD use count associated with the channel

              * The use count is incremented whenever a new channel

              * is obtained from this stream.

              */

            fd.decrementAndGetUseCount();

            channel.close();

         }

         /*

          * Decrement the FD use count associated with this stream

          */

         int useCount = fd.decrementAndGetUseCount();

         /*

          * If FileDescriptor is still in use by another stream, the finalizer

          * will not close it.

          */

         if ((useCount <= 0) || !isRunningFinalize()) {

             close0();

         }

     }

     /**

      * Returns the <code>FileDescriptor</code>

      * object  that represents the connection to

      * the actual file in the file system being

      * used by this <code>FileInputStream</code>.

      *

      * @return     the file descriptor object associated with this stream.

      * @exception  IOException  if an I/O error occurs.

      * @see        java.io.FileDescriptor

      */

     public final FileDescriptor getFD() throws IOException {

         if (fd != null) return fd;

         throw new IOException();

     }

     /**

      * Returns the unique {@link java.nio.channels.FileChannel FileChannel}

      * object associated with this file input stream.

      *

      * <p> The initial {@link java.nio.channels.FileChannel#position()

      * </code>position<code>} of the returned channel will be equal to the

      * number of bytes read from the file so far.  Reading bytes from this

      * stream will increment the channel's position.  Changing the channel's

      * position, either explicitly or by reading, will change this stream's

      * file position.

      *

      * @return  the file channel associated with this file input stream

      *

      * @since 1.4

      * @spec JSR-51

      */

     public FileChannel getChannel() {

         synchronized (this) {

             if (channel == null) {

                 channel = FileChannelImpl.open(fd, true, false, this);

                 /*

                  * Increment fd's use count. Invoking the channel's close()

                  * method will result in decrementing the use count set for

                  * the channel.

                  */

                 fd.incrementAndGetUseCount();

             }

             return channel;

         }

     }

     private static native void initIDs();

     private native void close0() throws IOException;

     static {

         initIDs();

     }

     /**

      * Ensures that the <code>close</code> method of this file input stream is

      * called when there are no more references to it.

      *

      * @exception  IOException  if an I/O error occurs.

      * @see        java.io.FileInputStream#close()

      */

     protected void finalize() throws IOException {

         if ((fd != null) &&  (fd != FileDescriptor.in)) {

             /*

              * Finalizer should not release the FileDescriptor if another

              * stream is still using it. If the user directly invokes

              * close() then the FileDescriptor is also released.

              */

             runningFinalize.set(Boolean.TRUE);

             try {

                 close();

             } finally {

                 runningFinalize.set(Boolean.FALSE);

             }

         }

     }

 }