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/* 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/DebugOnly.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(const FileDescriptor& aOther)
: mHandleCreatedByOtherProcess(false),
mHandleCreatedByOtherProcessWasUsed(false)
{
// Don't use operator= here because that will call
// CloseCurrentProcessHandle() on this (uninitialized) object.
Assign(aOther);
}
FileDescriptor(PlatformHandleType aHandle);
FileDescriptor(const IPDLPrivate&, const PickleType& aPickle)
#ifdef XP_WIN
: mHandle(aPickle)
#else
: mHandle(aPickle.fd)
#endif
, mHandleCreatedByOtherProcess(true)
, mHandleCreatedByOtherProcessWasUsed(false)
{ }
~FileDescriptor()
{
CloseCurrentProcessHandle();
}
FileDescriptor&
operator=(const FileDescriptor& aOther)
{
CloseCurrentProcessHandle();
Assign(aOther);
return *this;
}
// 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
{
return IsValid(mHandle);
}
PlatformHandleType
PlatformHandle() const
{
if (mHandleCreatedByOtherProcess) {
mHandleCreatedByOtherProcessWasUsed = true;
}
return mHandle;
}
bool
operator==(const FileDescriptor& aOther) const
{
return mHandle == aOther.mHandle;
}
private:
void
Assign(const FileDescriptor& aOther)
{
if (aOther.mHandleCreatedByOtherProcess) {
mHandleCreatedByOtherProcess = true;
mHandleCreatedByOtherProcessWasUsed =
aOther.mHandleCreatedByOtherProcessWasUsed;
mHandle = aOther.PlatformHandle();
} else {
DuplicateInCurrentProcess(aOther.PlatformHandle());
mHandleCreatedByOtherProcess = false;
mHandleCreatedByOtherProcessWasUsed = false;
}
}
static bool
IsValid(PlatformHandleType aHandle);
void
DuplicateInCurrentProcess(PlatformHandleType aHandle);
void
CloseCurrentProcessHandle();
PlatformHandleType mHandle;
// If this is true then this instance is created by IPDL to ferry a handle to
// its eventual consumer and we never close the handle. If this is false then
// we are a RAII wrapper around the handle and we close the handle on
// destruction.
bool mHandleCreatedByOtherProcess;
// This is to ensure that we don't leak the handle (which is only possible
// when we're in the receiving process).
mutable DebugOnly<bool> mHandleCreatedByOtherProcessWasUsed;
};
} // namespace ipc
} // namespace mozilla
#endif // mozilla_ipc_FileDescriptor_h
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