/*

 * 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

 * questions.

 */

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);

            }

        }

    }

}