michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef mozilla_ipc_FileDescriptor_h
michael@0: #define mozilla_ipc_FileDescriptor_h
michael@0: 
michael@0: #include "base/basictypes.h"
michael@0: #include "base/process.h"
michael@0: #include "mozilla/DebugOnly.h"
michael@0: #include "nscore.h"
michael@0: 
michael@0: #ifdef XP_WIN
michael@0: // Need the HANDLE typedef.
michael@0: #include <winnt.h>
michael@0: #else
michael@0: #include "base/file_descriptor_posix.h"
michael@0: #endif
michael@0: 
michael@0: namespace mozilla {
michael@0: namespace ipc {
michael@0: 
michael@0: // This class is used by IPDL to share file descriptors across processes. When
michael@0: // sending a FileDescriptor IPDL will first duplicate a platform-specific file
michael@0: // handle type ('PlatformHandleType') into a handle that is valid in the other
michael@0: // process. Then IPDL will convert the duplicated handle into a type suitable
michael@0: // for pickling ('PickleType') and then send that through the IPC pipe. In the
michael@0: // receiving process the pickled data is converted into a platform-specific file
michael@0: // handle and then returned to the receiver.
michael@0: //
michael@0: // To use this class add 'FileDescriptor' as an argument in the IPDL protocol
michael@0: // and then pass a file descriptor from C++ to the Call/Send method. The
michael@0: // Answer/Recv method will receive a FileDescriptor& on which PlatformHandle()
michael@0: // can be called to return the platform file handle.
michael@0: class FileDescriptor
michael@0: {
michael@0: public:
michael@0:   typedef base::ProcessHandle ProcessHandle;
michael@0: 
michael@0: #ifdef XP_WIN
michael@0:   typedef HANDLE PlatformHandleType;
michael@0:   typedef HANDLE PickleType;
michael@0: #else
michael@0:   typedef int PlatformHandleType;
michael@0:   typedef base::FileDescriptor PickleType;
michael@0: #endif
michael@0: 
michael@0:   // This should only ever be created by IPDL.
michael@0:   struct IPDLPrivate
michael@0:   {};
michael@0: 
michael@0:   FileDescriptor();
michael@0: 
michael@0:   FileDescriptor(const FileDescriptor& aOther)
michael@0:     : mHandleCreatedByOtherProcess(false),
michael@0:       mHandleCreatedByOtherProcessWasUsed(false)
michael@0:   {
michael@0:     // Don't use operator= here because that will call
michael@0:     // CloseCurrentProcessHandle() on this (uninitialized) object.
michael@0:     Assign(aOther);
michael@0:   }
michael@0: 
michael@0:   FileDescriptor(PlatformHandleType aHandle);
michael@0: 
michael@0:   FileDescriptor(const IPDLPrivate&, const PickleType& aPickle)
michael@0: #ifdef XP_WIN
michael@0:   : mHandle(aPickle)
michael@0: #else
michael@0:   : mHandle(aPickle.fd)
michael@0: #endif
michael@0:   , mHandleCreatedByOtherProcess(true)
michael@0:   , mHandleCreatedByOtherProcessWasUsed(false)
michael@0:   { }
michael@0: 
michael@0:   ~FileDescriptor()
michael@0:   {
michael@0:     CloseCurrentProcessHandle();
michael@0:   }
michael@0: 
michael@0:   FileDescriptor&
michael@0:   operator=(const FileDescriptor& aOther)
michael@0:   {
michael@0:     CloseCurrentProcessHandle();
michael@0:     Assign(aOther);
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0:   // Performs platform-specific actions to duplicate mHandle in the other
michael@0:   // process (e.g. dup() on POSIX, DuplicateHandle() on Windows). Returns a
michael@0:   // pickled value that can be passed to the other process via IPC.
michael@0:   PickleType
michael@0:   ShareTo(const IPDLPrivate&, ProcessHandle aOtherProcess) const;
michael@0: 
michael@0:   // Tests mHandle against a well-known invalid platform-specific file handle
michael@0:   // (e.g. -1 on POSIX, INVALID_HANDLE_VALUE on Windows).
michael@0:   bool
michael@0:   IsValid() const
michael@0:   {
michael@0:     return IsValid(mHandle);
michael@0:   }
michael@0: 
michael@0:   PlatformHandleType
michael@0:   PlatformHandle() const
michael@0:   {
michael@0:     if (mHandleCreatedByOtherProcess) {
michael@0:       mHandleCreatedByOtherProcessWasUsed = true;
michael@0:     }
michael@0:     return mHandle;
michael@0:   }
michael@0: 
michael@0:   bool
michael@0:   operator==(const FileDescriptor& aOther) const
michael@0:   {
michael@0:     return mHandle == aOther.mHandle;
michael@0:   }
michael@0: 
michael@0: private:
michael@0:   void
michael@0:   Assign(const FileDescriptor& aOther)
michael@0:   {
michael@0:     if (aOther.mHandleCreatedByOtherProcess) {
michael@0:       mHandleCreatedByOtherProcess = true;
michael@0:       mHandleCreatedByOtherProcessWasUsed =
michael@0:         aOther.mHandleCreatedByOtherProcessWasUsed;
michael@0:       mHandle = aOther.PlatformHandle();
michael@0:     } else {
michael@0:       DuplicateInCurrentProcess(aOther.PlatformHandle());
michael@0:       mHandleCreatedByOtherProcess = false;
michael@0:       mHandleCreatedByOtherProcessWasUsed = false;
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   static bool
michael@0:   IsValid(PlatformHandleType aHandle);
michael@0: 
michael@0:   void
michael@0:   DuplicateInCurrentProcess(PlatformHandleType aHandle);
michael@0: 
michael@0:   void
michael@0:   CloseCurrentProcessHandle();
michael@0: 
michael@0:   PlatformHandleType mHandle;
michael@0: 
michael@0:   // If this is true then this instance is created by IPDL to ferry a handle to
michael@0:   // its eventual consumer and we never close the handle. If this is false then
michael@0:   // we are a RAII wrapper around the handle and we close the handle on
michael@0:   // destruction.
michael@0:   bool mHandleCreatedByOtherProcess;
michael@0: 
michael@0:   // This is to ensure that we don't leak the handle (which is only possible
michael@0:   // when we're in the receiving process).
michael@0:   mutable DebugOnly<bool> mHandleCreatedByOtherProcessWasUsed;
michael@0: };
michael@0: 
michael@0: } // namespace ipc
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif // mozilla_ipc_FileDescriptor_h