src/java.base/windows/classes/java/io/FileDescriptor.java
changeset 47216 71c04702a3d5
parent 32834 e1dca5fe4de3
child 47235 9ef10c6e67b8
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/windows/classes/java/io/FileDescriptor.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,245 @@
+/*
+ * Copyright (c) 2003, 2015, 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.util.ArrayList;
+import java.util.List;
+import jdk.internal.misc.JavaIOFileDescriptorAccess;
+import jdk.internal.misc.SharedSecrets;
+
+/**
+ * Instances of the file descriptor class serve as an opaque handle
+ * to the underlying machine-specific structure representing an
+ * open file, an open socket, or another source or sink of bytes.
+ * The main practical use for a file descriptor is to create a
+ * {@link FileInputStream} or {@link FileOutputStream} to contain it.
+ *
+ * <p>Applications should not create their own file descriptors.
+ *
+ * @author  Pavani Diwanji
+ * @since   1.0
+ */
+public final class FileDescriptor {
+
+    private int fd;
+
+    private long handle;
+
+    private Closeable parent;
+    private List<Closeable> otherParents;
+    private boolean closed;
+
+    /**
+     * true, if file is opened for appending.
+     */
+    private boolean append;
+
+    /**
+     * Constructs an (invalid) FileDescriptor
+     * object.
+     */
+    public /**/ FileDescriptor() {
+        fd = -1;
+        handle = -1;
+    }
+
+    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) {
+                    obj.handle = handle;
+                }
+
+                public long getHandle(FileDescriptor obj) {
+                    return obj.handle;
+                }
+            }
+        );
+    }
+
+    /**
+     * A handle to the standard input stream. Usually, this file
+     * descriptor is not used directly, but rather via the input stream
+     * known as {@code System.in}.
+     *
+     * @see     java.lang.System#in
+     */
+    public static final FileDescriptor in = standardStream(0);
+
+    /**
+     * A handle to the standard output stream. Usually, this file
+     * descriptor is not used directly, but rather via the output stream
+     * known as {@code System.out}.
+     * @see     java.lang.System#out
+     */
+    public static final FileDescriptor out = standardStream(1);
+
+    /**
+     * A handle to the standard error stream. Usually, this file
+     * descriptor is not used directly, but rather via the output stream
+     * known as {@code System.err}.
+     *
+     * @see     java.lang.System#err
+     */
+    public static final FileDescriptor err = standardStream(2);
+
+    /**
+     * Tests if this file descriptor object is valid.
+     *
+     * @return  {@code true} if the file descriptor object represents a
+     *          valid, open file, socket, or other active I/O connection;
+     *          {@code false} otherwise.
+     */
+    public boolean valid() {
+        return ((handle != -1) || (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 FileDesecriptor 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();
+
+    private static native long set(int d);
+
+    private static FileDescriptor standardStream(int fd) {
+        FileDescriptor desc = new FileDescriptor();
+        desc.handle = set(fd);
+        return desc;
+    }
+
+    /*
+     * 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;
+            }
+        }
+    }
+}