FileInputStream or FileOutputStream to
+ * contain it.
+ *
+ * Applications should not create their own file descriptors.
+ *
+ * @author Pavani Diwanji
+ * @see java.io.FileInputStream
+ * @see java.io.FileOutputStream
+ * @since 1.0
+ */
+public final class FileDescriptor {
+
+ private int fd;
+
+ private Closeable parent;
+ private ListSystem.in.
+ *
+ * @see java.lang.System#in
+ */
+ public static final FileDescriptor in = new FileDescriptor(0);
+
+ /**
+ * A handle to the standard output stream. Usually, this file
+ * descriptor is not used directly, but rather via the output stream
+ * known as System.out.
+ * @see java.lang.System#out
+ */
+ public static final FileDescriptor out = new FileDescriptor(1);
+
+ /**
+ * A handle to the standard error stream. Usually, this file
+ * descriptor is not used directly, but rather via the output stream
+ * known as System.err.
+ *
+ * @see java.lang.System#err
+ */
+ public static final FileDescriptor err = new FileDescriptor(2);
+
+ /**
+ * Tests if this file descriptor object is valid.
+ *
+ * @return true if the file descriptor object represents a
+ * valid, open file, socket, or other active I/O connection;
+ * false otherwise.
+ */
+ public boolean valid() {
+ return fd != -1;
+ }
+
+ /**
+ * Force all system buffers to synchronize with the underlying
+ * device. This method returns after all modified data and
+ * attributes of this FileDescriptor have been written to the
+ * relevant device(s). In particular, if this FileDescriptor
+ * refers to a physical storage medium, such as a file in a file
+ * system, sync will not return until all in-memory modified copies
+ * of buffers associated with this FileDescriptor have been
+ * written to the physical medium.
+ *
+ * sync is meant to be used by code that requires physical
+ * storage (such as a file) to be in a known state For
+ * example, a class that provided a simple transaction facility
+ * might use sync to ensure that all changes to a file caused
+ * by a given transaction were recorded on a storage medium.
+ *
+ * sync only affects buffers downstream of this FileDescriptor. If
+ * any in-memory buffering is being done by the application (for
+ * example, by a BufferedOutputStream object), those buffers must
+ * be flushed into the FileDescriptor (for example, by invoking
+ * OutputStream.flush) before that data will be affected by sync.
+ *
+ * @exception SyncFailedException
+ * Thrown when the buffers cannot be flushed,
+ * or because the system cannot guarantee that all the
+ * buffers have been synchronized with physical media.
+ * @since 1.1
+ */
+ public native void sync() throws SyncFailedException;
+
+ /* This routine initializes JNI field offsets for the class */
+ private static native void initIDs();
+
+ static {
+ initIDs();
+ }
+
+ // Set up JavaIOFileDescriptorAccess in SharedSecrets
+ static {
+ SharedSecrets.setJavaIOFileDescriptorAccess(
+ new JavaIOFileDescriptorAccess() {
+ public void set(FileDescriptor obj, int fd) {
+ obj.fd = fd;
+ }
+
+ public int get(FileDescriptor obj) {
+ return obj.fd;
+ }
+
+ public void setAppend(FileDescriptor obj, boolean append) {
+ obj.append = append;
+ }
+
+ public boolean getAppend(FileDescriptor obj) {
+ return obj.append;
+ }
+
+ public void setHandle(FileDescriptor obj, long handle) {
+ throw new UnsupportedOperationException();
+ }
+
+ public long getHandle(FileDescriptor obj) {
+ throw new UnsupportedOperationException();
+ }
+ }
+ );
+ }
+
+ /**
+ * Returns true, if the file was opened for appending.
+ */
+ private static native boolean getAppend(int fd);
+
+ /*
+ * Package private methods to track referents.
+ * If multiple streams point to the same FileDescriptor, we cycle
+ * through the list of all referents and call close()
+ */
+
+ /**
+ * Attach a Closeable to this FD for tracking.
+ * parent reference is added to otherParents when
+ * needed to make closeAll simpler.
+ */
+ synchronized void attach(Closeable c) {
+ if (parent == null) {
+ // first caller gets to do this
+ parent = c;
+ } else if (otherParents == null) {
+ otherParents = new ArrayList<>();
+ otherParents.add(parent);
+ otherParents.add(c);
+ } else {
+ otherParents.add(c);
+ }
+ }
+
+ /**
+ * Cycle through all Closeables sharing this FD and call
+ * close() on each one.
+ *
+ * The caller closeable gets to call close0().
+ */
+ @SuppressWarnings("try")
+ synchronized void closeAll(Closeable releaser) throws IOException {
+ if (!closed) {
+ closed = true;
+ IOException ioe = null;
+ try (releaser) {
+ if (otherParents != null) {
+ for (Closeable referent : otherParents) {
+ try {
+ referent.close();
+ } catch(IOException x) {
+ if (ioe == null) {
+ ioe = x;
+ } else {
+ ioe.addSuppressed(x);
+ }
+ }
+ }
+ }
+ } catch(IOException ex) {
+ /*
+ * If releaser close() throws IOException
+ * add other exceptions as suppressed.
+ */
+ if (ioe != null)
+ ex.addSuppressed(ioe);
+ ioe = ex;
+ } finally {
+ if (ioe != null)
+ throw ioe;
+ }
+ }
+ }
+}