/*
* Copyright (c) 1994, 2017, 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>.
*
* @apiNote
* To release resources used by this stream {@link #close} should be called
* directly or by try-with-resources. Subclasses are responsible for the cleanup
* of resources acquired by the subclass.
* Subclasses that override {@link #finalize} in order to perform cleanup
* should be modified to use alternative cleanup mechanisms such as
* {@link java.lang.ref.Cleaner} and remove the overriding {@code finalize} method.
*
* @implSpec
* If this FileInputStream has been subclassed and the {@link #close}
* method has been overridden, the {@link #close} method will be
* called when the FileInputStream is unreachable.
* Otherwise, it is implementation specific how the resource cleanup described in
* {@link #close} is performed.
*
* @author Arthur van Hoff
* @see java.io.File
* @see java.io.FileDescriptor
* @see java.io.FileOutputStream
* @see java.nio.file.Files#newInputStream
* @since 1.0
*/
public
class FileInputStream extends InputStream
{
/* File Descriptor - handle to the open file */
private final FileDescriptor fd;
/**
* The path of the referenced file
* (null if the stream is created with a file descriptor)
*/
private final String path;
private volatile FileChannel channel;
private final Object closeLock = new Object();
private volatile boolean closed;
private final Object altFinalizer;
/**
* 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();
}
if (file.isInvalid()) {
throw new FileNotFoundException("Invalid file path");
}
fd = new FileDescriptor();
fd.attach(this);
path = name;
open(name);
altFinalizer = getFinalizer(this);
if (altFinalizer == null) {
FileCleanable.register(fd); // open set the fd, register the cleanup
}
}
/**
* 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;
path = null;
altFinalizer = null;
/*
* FileDescriptor is being shared by streams.
* Register this stream with FileDescriptor tracker.
*/
fd.attach(this);
}
/**
* Opens the specified file for reading.
* @param name the name of the file
*/
private native void open0(String name) throws FileNotFoundException;
// wrap native call to allow instrumentation
/**
* Opens the specified file for reading.
* @param name the name of the file
*/
private void open(String name) throws FileNotFoundException {
open0(name);
}
/**
* 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 int read() throws IOException {
return read0();
}
private native int read0() 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, the method
* will try to skip backwards. In case the backing file does not support
* backward skip at its current position, an <code>IOException</code> is
* thrown. The actual number of bytes skipped is returned. If it skips
* forwards, it returns a positive value. If it skips backwards, it
* returns a negative value.
*
* <p>This method may skip more bytes than what 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 long skip(long n) throws IOException {
return skip0(n);
}
private native long skip0(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. Returns 0 when the file
* position is beyond EOF. 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 int available() throws IOException {
return available0();
}
private native int available0() 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.
*
* @apiNote
* Overriding {@link #close} to perform cleanup actions is reliable
* only when called directly or when called by try-with-resources.
* Do not depend on finalization to invoke {@code close};
* finalization is not reliable and is deprecated.
* If cleanup of native resources is needed, other mechanisms such as
* {@linkplain java.lang.ref.Cleaner} should be used.
*
* @exception IOException if an I/O error occurs.
*
* @revised 1.4
* @spec JSR-51
*/
public void close() throws IOException {
if (closed) {
return;
}
synchronized (closeLock) {
if (closed) {
return;
}
closed = true;
}
FileChannel fc = channel;
if (fc != null) {
// possible race with getChannel(), benign since
// FileChannel.close is final and idempotent
fc.close();
}
fd.closeAll(new Closeable() {
public void close() throws IOException {
fd.close();
}
});
}
/**
* 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()
* position} 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() {
FileChannel fc = this.channel;
if (fc == null) {
synchronized (this) {
fc = this.channel;
if (fc == null) {
this.channel = fc = FileChannelImpl.open(fd, path, true,
false, false, this);
if (closed) {
try {
// possible race with close(), benign since
// FileChannel.close is final and idempotent
fc.close();
} catch (IOException ioe) {
throw new InternalError(ioe); // should not happen
}
}
}
}
}
return fc;
}
private static native void initIDs();
static {
initIDs();
}
/**
* Ensures that the {@link #close} method of this file input stream is
* called when there are no more references to it.
* The {@link #finalize} method does not call {@link #close} directly.
*
* @apiNote
* To release resources used by this stream {@link #close} should be called
* directly or by try-with-resources.
*
* @implSpec
* If this FileInputStream has been subclassed and the {@link #close}
* method has been overridden, the {@link #close} method will be
* called when the FileInputStream is unreachable.
* Otherwise, it is implementation specific how the resource cleanup described in
* {@link #close} is performed.
*
* @deprecated The {@code finalize} method has been deprecated and will be removed.
* Subclasses that override {@code finalize} in order to perform cleanup
* should be modified to use alternative cleanup mechanisms and
* to remove the overriding {@code finalize} method.
* When overriding the {@code finalize} method, its implementation must explicitly
* ensure that {@code super.finalize()} is invoked as described in {@link Object#finalize}.
* See the specification for {@link Object#finalize()} for further
* information about migration options.
*
* @exception IOException if an I/O error occurs.
* @see java.io.FileInputStream#close()
*/
@Deprecated(since="9", forRemoval = true)
protected void finalize() throws IOException {
}
/*
* Returns a finalizer object if the FIS needs a finalizer; otherwise null.
* If the FIS has a close method; it needs an AltFinalizer.
*/
private static Object getFinalizer(FileInputStream fis) {
Class<?> clazz = fis.getClass();
while (clazz != FileInputStream.class) {
try {
clazz.getDeclaredMethod("close");
return new AltFinalizer(fis);
} catch (NoSuchMethodException nsme) {
// ignore
}
clazz = clazz.getSuperclass();
}
return null;
}
/**
* Class to call {@code FileInputStream.close} when finalized.
* If finalization of the stream is needed, an instance is created
* in its constructor(s). When the set of instances
* related to the stream is unreachable, the AltFinalizer performs
* the needed call to the stream's {@code close} method.
*/
static class AltFinalizer {
private final FileInputStream fis;
AltFinalizer(FileInputStream fis) {
this.fis = fis;
}
@Override
@SuppressWarnings("deprecation")
protected final void finalize() {
try {
if ((fis.fd != null) && (fis.fd != FileDescriptor.in)) {
/* if fd is shared, the references in FileDescriptor
* will ensure that finalizer is only called when
* safe to do so. All references using the fd have
* become unreachable. We can call close()
*/
fis.close();
}
} catch (IOException ioe) {
// ignore
}
}
}
}