Source code

Revision control

Other Tools

/* -*- 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 */
#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"
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 {
typedef base::ProcessId ProcessId;
using UniquePlatformHandle = mozilla::UniqueFileHandle;
using PlatformHandleType = UniquePlatformHandle::ElementType;
#ifdef XP_WIN
typedef PlatformHandleType PickleType;
typedef base::FileDescriptor PickleType;
// This should only ever be created by IPDL.
struct IPDLPrivate {};
// Represents an invalid handle.
// 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& 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;
static UniqueFileHandle Clone(PlatformHandleType aHandle);
UniquePlatformHandle mHandle;
} // namespace ipc
} // namespace mozilla
#endif // mozilla_ipc_FileDescriptor_h