ipc/glue/FileDescriptor.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_ipc_FileDescriptor_h
   8 #define mozilla_ipc_FileDescriptor_h
   9
  10 #include "base/basictypes.h"
  11 #include "base/process.h"
  12 #include "mozilla/UniquePtrExtensions.h"
  13
  14 namespace mozilla {
  15 namespace ipc {
  16
  17 // This class is used by IPDL to share file descriptors across processes. When
  18 // sending a FileDescriptor, IPDL will transfer a duplicate of the handle into
  19 // the remote process.
  20 //
  21 // To use this class add 'FileDescriptor' as an argument in the IPDL protocol
  22 // and then pass a file descriptor from C++ to the Send method. The Recv method
  23 // will receive a FileDescriptor& on which PlatformHandle() can be called to
  24 // return the platform file handle.
  25 class FileDescriptor {
  26  public:
  27   typedef base::ProcessId ProcessId;
  28
  29   using UniquePlatformHandle = mozilla::UniqueFileHandle;
  30   using PlatformHandleType = UniquePlatformHandle::ElementType;
  31
  32   // This should only ever be created by IPDL.
  33   struct IPDLPrivate {};
  34
  35   // Represents an invalid handle.
  36   FileDescriptor();
  37
  38   // Copy constructor will duplicate a new handle.
  39   FileDescriptor(const FileDescriptor& aOther);
  40
  41   FileDescriptor(FileDescriptor&& aOther);
  42
  43   // This constructor will duplicate a new handle.
  44   // The caller still have to close aHandle.
  45   explicit FileDescriptor(PlatformHandleType aHandle);
  46
  47   explicit FileDescriptor(UniquePlatformHandle&& aHandle);
  48
  49   ~FileDescriptor();
  50
  51   FileDescriptor& operator=(const FileDescriptor& aOther);
  52
  53   FileDescriptor& operator=(FileDescriptor&& aOther);
  54
  55   // Tests mHandle against a well-known invalid platform-specific file handle
  56   // (e.g. -1 on POSIX, INVALID_HANDLE_VALUE on Windows).
  57   bool IsValid() const;
  58
  59   // Returns a duplicated handle, it is caller's responsibility to close the
  60   // handle.
  61   UniquePlatformHandle ClonePlatformHandle() const;
  62
  63   // Extracts the underlying handle and makes this object an invalid handle.
  64   // (Compare UniquePtr::release.)
  65   UniquePlatformHandle TakePlatformHandle();
  66
  67   // Only used in nsTArray.
  68   bool operator==(const FileDescriptor& aOther) const;
  69
  70  private:
  71   static UniqueFileHandle Clone(PlatformHandleType aHandle);
  72
  73   UniquePlatformHandle mHandle;
  74 };
  75
  76 }  // namespace ipc
  77 }  // namespace mozilla
  78
  79 #endif  // mozilla_ipc_FileDescriptor_h