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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/UniquePtr.h"
+
+#ifdef XP_WIN
+// Need the HANDLE typedef.
+#include <winnt.h>
+#else
+#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;
+
+#ifdef XP_WIN
+ typedef HANDLE PlatformHandleType;
+ typedef HANDLE PickleType;
+#else
+ typedef int PlatformHandleType;
+ typedef base::FileDescriptor PickleType;
+#endif
+
+ struct PlatformHandleHelper
+ {
+ MOZ_IMPLICIT PlatformHandleHelper(PlatformHandleType aHandle);
+ MOZ_IMPLICIT PlatformHandleHelper(std::nullptr_t);
+ bool operator != (std::nullptr_t) const;
+ operator PlatformHandleType () const;
+#ifdef XP_WIN
+ operator std::intptr_t () const;
+#endif
+ private:
+ PlatformHandleType mHandle;
+ };
+ struct PlatformHandleDeleter
+ {
+ typedef PlatformHandleHelper pointer;
+ void operator () (PlatformHandleHelper aHelper);
+ };
+ typedef UniquePtr<PlatformHandleType, PlatformHandleDeleter> UniquePlatformHandle;
+
+ // 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);
+
+ // 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;
+
+ // Only used in nsTArray.
+ bool
+ operator==(const FileDescriptor& aOther) const;
+
+private:
+ friend struct PlatformHandleTrait;
+
+ void
+ Assign(const FileDescriptor& aOther);
+
+ void
+ Close();
+
+ static bool
+ IsValid(PlatformHandleType aHandle);
+
+ static PlatformHandleType
+ Clone(PlatformHandleType aHandle);
+
+ static void
+ Close(PlatformHandleType aHandle);
+
+ PlatformHandleType mHandle;
+};
+
+} // namespace ipc
+} // namespace mozilla
+
+#endif // mozilla_ipc_FileDescriptor_h