/*
 * @(#)FileInputStream.java	1.68 06/04/07
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

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
 * @version 1.68, 04/07/06
 * @see     java.io.File
 * @see     java.io.FileDescriptor
 * @see	    java.io.FileOutputStream
 * @since   JDK1.0
 */
public
class FileInputStream extends InputStream
{
    /* File Descriptor - handle to the open file */
    private FileDescriptor fd;

    private FileChannel channel = null;

    /**
     * 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();
	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.
     *
     * @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;
    }

    /**
     * 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 {
        if (channel != null)
            channel.close();
        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);
	    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) {
	    if (fd != fd.in) {
		close();
	    }
	}
    }
}