FileInputStream obtains input bytes
* from a file in a file system. What files
* are available depends on the host environment.
*
* FileInputStream is meant for reading streams of raw bytes
* such as image data. For reading streams of characters, consider using
* FileReader.
*
* @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;
/**
* The path of the referenced file
* (null if the stream is created with a file descriptor)
*/
private final String path;
private FileChannel channel = null;
private final Object closeLock = new Object();
private volatile boolean closed = false;
private final boolean isFdOwner;
private final CloseGuard guard = CloseGuard.get();
private final IoTracker tracker = new IoTracker();
/**
* Creates a FileInputStream by
* opening a connection to an actual file,
* the file named by the path name name
* in the file system. A new FileDescriptor
* object is created to represent this file
* connection.
*
* First, if there is a security
* manager, its checkRead method
* is called with the 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
* FileNotFoundException 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
* 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 FileInputStream by
* opening a connection to an actual file,
* the file named by the File
* object file in the file system.
* A new FileDescriptor object
* is created to represent this file connection.
*
* First, if there is a security manager,
* its checkRead method is called
* with the path represented by the 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
* FileNotFoundException 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
* 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);
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();
isFdOwner = true;
this.path = name;
BlockGuard.getThreadPolicy().onReadFromDisk();
open(name);
guard.open("close");
}
/**
* Creates a FileInputStream by using the file descriptor
* fdObj, which represents an existing connection to an
* actual file in the file system.
*
* If there is a security manager, its checkRead method is
* called with the file descriptor 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 SecurityException is thrown.
*
* If fdObj is null then a NullPointerException
* is thrown.
*
* This constructor does not throw an exception if 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 IOException is thrown.
*
* @param fdObj the file descriptor to be opened for reading.
*/
public FileInputStream(FileDescriptor fdObj) {
this(fdObj, false /* isFdOwner */);
}
/** @hide */
public FileInputStream(FileDescriptor fdObj, boolean isFdOwner) {
if (fdObj == null) {
throw new NullPointerException("fdObj == null");
}
fd = fdObj;
this.isFdOwner = isFdOwner;
path = null;
}
/**
* 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 -1 if the end of the
* file is reached.
* @exception IOException if an I/O error occurs.
*/
public int read() throws IOException {
byte[] b = new byte[1];
return (read(b, 0, 1) != -1) ? b[0] & 0xff : -1;
}
/**
* Reads up to 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
* -1 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 read(b, 0, b.length);
}
/**
* Reads up to len bytes of data from this input stream
* into an array of bytes. If len is not zero, the method
* blocks until some input is available; otherwise, no
* bytes are read and 0 is returned.
*
* @param b the buffer into which the data is read.
* @param off the start offset in the destination array b
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* -1 if there is no more data because the end of
* the file has been reached.
* @exception NullPointerException If b is null.
* @exception IndexOutOfBoundsException If off is negative,
* len is negative, or len is greater than
* b.length - off
* @exception IOException if an I/O error occurs.
*/
public int read(byte b[], int off, int len) throws IOException {
if (closed && len > 0) {
throw new IOException("Stream Closed");
}
tracker.trackIo(len);
return IoBridge.read(fd, b, off, len);
}
/**
* Skips over and discards n bytes of data from the
* input stream.
*
*
The skip method may, for a variety of
* reasons, end up skipping over some smaller number of bytes,
* possibly 0. If 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 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. * @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 { if (closed) { throw new IOException("Stream Closed"); } try { BlockGuard.getThreadPolicy().onReadFromDisk(); return skip0(n); } catch(UseManualSkipException e) { return super.skip(n); } } private native long skip0(long n) throws IOException, UseManualSkipException; /* * Used to force manual skip when FileInputStream operates on pipe */ private static class UseManualSkipException extends Exception { } /** * 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. * @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 { if (closed) { throw new IOException("Stream Closed"); } 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.
*
* @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;
}
guard.close();
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.
*/
channel.close();
}
if (isFdOwner) {
IoBridge.closeAndSignalBlockedThreads(fd);
}
}
/**
* Returns the FileDescriptor
* object that represents the connection to
* the actual file in the file system being
* used by this FileInputStream.
*
* @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.
*
*
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() {
synchronized (this) {
if (channel == null) {
channel = FileChannelImpl.open(fd, path, true, false, this);
}
return channel;
}
}
/**
* Ensures that the close 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 (guard != null) {
guard.warnIfOpen();
}
if ((fd != null) && (fd != FileDescriptor.in)) {
close();
}
}
}