1 files changed, 102 insertions, 0 deletions
diff --git a/ipc/glue/FileDescriptor.h b/ipc/glue/FileDescriptor.h
new file mode 100644
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+++ b/ipc/glue/FileDescriptor.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_FileDescriptor_h
+#define mozilla_ipc_FileDescriptor_h
+
+#include "base/basictypes.h"
+#include "base/process.h"
+#include "mozilla/UniquePtrExtensions.h"
+
+#ifdef XP_UNIX
+#  include "base/file_descriptor_posix.h"
+#endif
+
+namespace mozilla {
+namespace ipc {
+
+// This class is used by IPDL to share file descriptors across processes. When
+// sending a FileDescriptor IPDL will first duplicate a platform-specific file
+// handle type ('PlatformHandleType') into a handle that is valid in the other
+// process. Then IPDL will convert the duplicated handle into a type suitable
+// for pickling ('PickleType') and then send that through the IPC pipe. In the
+// receiving process the pickled data is converted into a platform-specific file
+// handle and then returned to the receiver.
+//
+// To use this class add 'FileDescriptor' as an argument in the IPDL protocol
+// and then pass a file descriptor from C++ to the Call/Send method. The
+// Answer/Recv method will receive a FileDescriptor& on which PlatformHandle()
+// can be called to return the platform file handle.
+class FileDescriptor {
+ public:
+  typedef base::ProcessId ProcessId;
+
+  using UniquePlatformHandle = mozilla::UniqueFileHandle;
+  using PlatformHandleType = UniquePlatformHandle::ElementType;
+
+#ifdef XP_WIN
+  typedef PlatformHandleType PickleType;
+#else
+  typedef base::FileDescriptor PickleType;
+#endif
+
+  // This should only ever be created by IPDL.
+  struct IPDLPrivate {};
+
+  // Represents an invalid handle.
+  FileDescriptor();
+
+  // Copy constructor will duplicate a new handle.
+  FileDescriptor(const FileDescriptor& aOther);
+
+  FileDescriptor(FileDescriptor&& aOther);
+
+  // This constructor will duplicate a new handle.
+  // The caller still have to close aHandle.
+  explicit FileDescriptor(PlatformHandleType aHandle);
+
+  explicit FileDescriptor(UniquePlatformHandle&& aHandle);
+
+  // This constructor WILL NOT duplicate the handle.
+  // FileDescriptor takes the ownership from IPC message.
+  FileDescriptor(const IPDLPrivate&, const PickleType& aPickle);
+
+  ~FileDescriptor();
+
+  FileDescriptor& operator=(const FileDescriptor& aOther);
+
+  FileDescriptor& operator=(FileDescriptor&& aOther);
+
+  // Performs platform-specific actions to duplicate mHandle in the other
+  // process (e.g. dup() on POSIX, DuplicateHandle() on Windows). Returns a
+  // pickled value that can be passed to the other process via IPC.
+  PickleType ShareTo(const IPDLPrivate&, ProcessId aTargetPid) const;
+
+  // Tests mHandle against a well-known invalid platform-specific file handle
+  // (e.g. -1 on POSIX, INVALID_HANDLE_VALUE on Windows).
+  bool IsValid() const;
+
+  // Returns a duplicated handle, it is caller's responsibility to close the
+  // handle.
+  UniquePlatformHandle ClonePlatformHandle() const;
+
+  // Extracts the underlying handle and makes this object an invalid handle.
+  // (Compare UniquePtr::release.)
+  UniquePlatformHandle TakePlatformHandle();
+
+  // Only used in nsTArray.
+  bool operator==(const FileDescriptor& aOther) const;
+
+ private:
+  static UniqueFileHandle Clone(PlatformHandleType aHandle);
+
+  UniquePlatformHandle mHandle;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_FileDescriptor_h