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/*
* Copyright (c) 1994, 2021, 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
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*/
package java.io;
import java.nio.channels.FileChannel;
import java.util.Arrays;
import jdk.internal.util.ArraysSupport;
import sun.nio.ch.FileChannelImpl;
/**
* A {@code FileInputStream} obtains input bytes
* from a file in a file system. What files
* are available depends on the host environment.
*
* {@code FileInputStream} is meant for reading streams of raw bytes
* such as image data. For reading streams of characters, consider using
* {@code FileReader}.
*
* @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
{
private static final int DEFAULT_BUFFER_SIZE = 8192;
/* 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;
/**
* Creates a {@code FileInputStream} by
* opening a connection to an actual file,
* the file named by the path name {@code name}
* in the file system. A new {@code FileDescriptor}
* object is created to represent this file
* connection.
*
* First, if there is a security
* manager, its {@code checkRead} method
* is called with the {@code name} argument
* as its argument.
*
* 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} is thrown.
*
* @param name the system-dependent file name.
* @throws 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.
* @throws SecurityException if a security manager exists and its
* {@code checkRead} 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} by
* opening a connection to an actual file,
* the file named by the {@code File}
* object {@code file} in the file system.
* A new {@code FileDescriptor} object
* is created to represent this file connection.
*
* First, if there is a security manager,
* its {@code checkRead} method is called
* with the path represented by the {@code file}
* argument as its argument.
*
* 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} is thrown.
*
* @param file the file to be opened for reading.
* @throws 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.
* @throws SecurityException if a security manager exists and its
* {@code checkRead} 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);
@SuppressWarnings("removal")
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);
FileCleanable.register(fd); // open set the fd, register the cleanup
}
/**
* Creates a {@code FileInputStream} by using the file descriptor
* {@code fdObj}, which represents an existing connection to an
* actual file in the file system.
*
* If there is a security manager, its {@code checkRead} method is
* called with the file descriptor {@code fdObj} 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} is thrown.
*
* If {@code fdObj} is null then a {@code NullPointerException}
* is thrown.
*
* This constructor does not throw an exception if {@code fdObj}
* 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} is thrown.
*
* @param fdObj the file descriptor to be opened for reading.
* @throws SecurityException if a security manager exists and its
* {@code checkRead} method denies read access to the
* file descriptor.
* @see SecurityManager#checkRead(java.io.FileDescriptor)
*/
public FileInputStream(FileDescriptor fdObj) {
@SuppressWarnings("removal")
SecurityManager security = System.getSecurityManager();
if (fdObj == null) {
throw new NullPointerException();
}
if (security != null) {
security.checkRead(fdObj);
}
fd = fdObj;
path = 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} if the end of the
* file is reached.
* @throws 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
* @throws 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} 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} if there is no more data because the end of
* the file has been reached.
* @throws 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} bytes of data from this input stream
* into an array of bytes. If {@code len} is not zero, the method
* blocks until some input is available; otherwise, no
* bytes are read and {@code 0} is returned.
*
* @param b the buffer into which the data is read.
* @param off the start offset in the destination array {@code b}
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* {@code -1} if there is no more data because the end of
* the file has been reached.
* @throws NullPointerException If {@code b} is {@code null}.
* @throws IndexOutOfBoundsException If {@code off} is negative,
* {@code len} is negative, or {@code len} is greater than
* {@code b.length - off}
* @throws IOException if an I/O error occurs.
*/
public int read(byte b[], int off, int len) throws IOException {
return readBytes(b, off, len);
}
public byte[] readAllBytes() throws IOException {
long length = length();
long position = position();
long size = length - position;
if (length <= 0 || size <= 0)
return super.readAllBytes();
if (size > (long) Integer.MAX_VALUE) {
String msg =
String.format("Required array size too large for %s: %d = %d - %d",
path, size, length, position);
throw new OutOfMemoryError(msg);
}
int capacity = (int)size;
byte[] buf = new byte[capacity];
int nread = 0;
int n;
for (;;) {
// read to EOF which may read more or less than initial size, e.g.,
// file is truncated while we are reading
while ((n = read(buf, nread, capacity - nread)) > 0)
nread += n;
// if last call to read() returned -1, we are done; otherwise,
// try to read one more byte and if that fails we're done too
if (n < 0 || (n = read()) < 0)
break;
// one more byte was read; need to allocate a larger buffer
capacity = Math.max(ArraysSupport.newLength(capacity,
1, // min growth
capacity), // pref growth
DEFAULT_BUFFER_SIZE);
buf = Arrays.copyOf(buf, capacity);
buf[nread++] = (byte)n;
}
return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
}
public byte[] readNBytes(int len) throws IOException {
if (len < 0)
throw new IllegalArgumentException("len < 0");
if (len == 0)
return new byte[0];
long length = length();
long position = position();
long size = length - position;
if (length <= 0 || size <= 0)
return super.readNBytes(len);
int capacity = (int)Math.min(len, size);
byte[] buf = new byte[capacity];
int remaining = capacity;
int nread = 0;
int n;
do {
n = read(buf, nread, remaining);
if (n > 0 ) {
nread += n;
remaining -= n;
} else if (n == 0) {
// Block until a byte is read or EOF is detected
byte b = (byte)read();
if (b == -1 )
break;
buf[nread++] = b;
remaining--;
}
} while (n >= 0 && remaining > 0);
return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
}
private long length() throws IOException {
return length0();
}
private native long length0() throws IOException;
private long position() throws IOException {
return position0();
}
private native long position0() throws IOException;
/**
* Skips over and discards {@code n} bytes of data from the
* input stream.
*
*
The {@code skip} method may, for a variety of
* reasons, end up skipping over some smaller number of bytes,
* possibly {@code 0}. If {@code n} 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} 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.
*
*
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.
* @throws 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.
*
*
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.
* @throws 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.
*
*
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.
*
* @throws IOException if an I/O error occurs.
*
* @revised 1.4
*/
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}
* object that represents the connection to
* the actual file in the file system being
* used by this {@code FileInputStream}.
*
* @return the file descriptor object associated with this stream.
* @throws 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.
*
*
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
*/
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();
}
}