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/* -*- 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_CrossProcessSemaphore_h
#define mozilla_CrossProcessSemaphore_h
#include "base/process.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/Maybe.h"
#if defined(OS_WIN)
# include "mozilla/UniquePtrExtensions.h"
#if !defined(OS_WIN) && !defined(OS_MACOSX)
# include <pthread.h>
# include <semaphore.h>
# include "mozilla/ipc/SharedMemoryBasic.h"
# include "mozilla/Atomics.h"
namespace IPC {
template <typename T>
struct ParamTraits;
} // namespace IPC
// Provides:
// - CrossProcessSemaphore, a semaphore that can be shared across processes
namespace mozilla {
template <typename T>
inline bool IsHandleValid(const T& handle) {
return bool(handle);
#if defined(OS_WIN)
typedef mozilla::UniqueFileHandle CrossProcessSemaphoreHandle;
#elif !defined(OS_MACOSX)
typedef mozilla::ipc::SharedMemoryBasic::Handle CrossProcessSemaphoreHandle;
template <>
inline bool IsHandleValid<CrossProcessSemaphoreHandle>(
const CrossProcessSemaphoreHandle& handle) {
return !(handle == mozilla::ipc::SharedMemoryBasic::NULLHandle());
// Stub for other platforms. We can't use uintptr_t here since different
// processes could disagree on its size.
typedef uintptr_t CrossProcessSemaphoreHandle;
class CrossProcessSemaphore {
* CrossProcessSemaphore
* @param name A name which can reference this lock (currently unused)
static CrossProcessSemaphore* Create(const char* aName,
uint32_t aInitialValue);
* CrossProcessSemaphore
* @param handle A handle of an existing cross process semaphore that can be
* opened.
static CrossProcessSemaphore* Create(CrossProcessSemaphoreHandle aHandle);
* Decrements the current value of the semaphore. This will block if the
* current value of the semaphore is 0, up to a maximum of aWaitTime (if
* specified).
* Returns true if the semaphore was succesfully decremented, false otherwise.
bool Wait(const Maybe<TimeDuration>& aWaitTime = Nothing());
* Increments the current value of the semaphore.
void Signal();
* CloneHandle
* This function is called to generate a serializable structure that can
* be sent to the specified process and opened on the other side.
* @returns A handle that can be shared to another process
CrossProcessSemaphoreHandle CloneHandle();
void CloseHandle();
friend struct IPC::ParamTraits<CrossProcessSemaphore>;
CrossProcessSemaphore(const CrossProcessSemaphore&);
CrossProcessSemaphore& operator=(const CrossProcessSemaphore&);
#if defined(OS_WIN)
explicit CrossProcessSemaphore(HANDLE aSemaphore);
HANDLE mSemaphore;
#elif !defined(OS_MACOSX)
RefPtr<mozilla::ipc::SharedMemoryBasic> mSharedBuffer;
sem_t* mSemaphore;
mozilla::Atomic<int32_t>* mRefCount;
} // namespace mozilla