gecko-dev/ipc/glue/FileDescriptor.h

96 строки
2.6 KiB
C++

/* 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 "nscore.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::ProcessHandle ProcessHandle;
#ifdef XP_WIN
typedef HANDLE PlatformHandleType;
typedef HANDLE PickleType;
#else
typedef int PlatformHandleType;
typedef base::FileDescriptor PickleType;
#endif
// This should only ever be created by IPDL.
struct IPDLPrivate
{};
FileDescriptor();
FileDescriptor(PlatformHandleType aHandle)
: mHandle(aHandle)
{ }
FileDescriptor(const IPDLPrivate&, const PickleType& aPickle)
#ifdef XP_WIN
: mHandle(aPickle)
#else
: mHandle(aPickle.fd)
#endif
{ }
// 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&, ProcessHandle aOtherProcess) 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;
PlatformHandleType
PlatformHandle() const
{
return mHandle;
}
bool
operator==(const FileDescriptor& aOther) const
{
return mHandle == aOther.mHandle;
}
private:
PlatformHandleType mHandle;
};
} // namespace ipc
} // namespace mozilla
#endif // mozilla_ipc_FileDescriptor_h