gecko-dev/xpcom/glue/nsThreadUtils.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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 nsThreadUtils_h__
#define nsThreadUtils_h__
#include "prthread.h"
#include "prinrval.h"
#include "nsIThreadManager.h"
#include "nsIThread.h"
#include "nsIRunnable.h"
#include "nsICancelableRunnable.h"
#include "nsStringGlue.h"
#include "nsCOMPtr.h"
#include "nsAutoPtr.h"
#include "mozilla/threads/nsThreadIDs.h"
#include "mozilla/Likely.h"
//-----------------------------------------------------------------------------
// These methods are alternatives to the methods on nsIThreadManager, provided
// for convenience.
/**
* Set name of the target thread. This operation is asynchronous.
*/
extern NS_COM_GLUE void
NS_SetThreadName(nsIThread *thread, const nsACString &name);
/**
* Static length version of the above function checking length of the
* name at compile time.
*/
template <size_t LEN>
inline NS_COM_GLUE void
NS_SetThreadName(nsIThread *thread, const char (&name)[LEN])
{
MOZ_STATIC_ASSERT(LEN <= 16,
"Thread name must be no more than 16 characters");
NS_SetThreadName(thread, nsDependentCString(name));
}
/**
* Create a new thread, and optionally provide an initial event for the thread.
*
* @param result
* The resulting nsIThread object.
* @param initialEvent
* The initial event to run on this thread. This parameter may be null.
* @param stackSize
* The size in bytes to reserve for the thread's stack.
*
* @returns NS_ERROR_INVALID_ARG
* Indicates that the given name is not unique.
*/
extern NS_COM_GLUE NS_METHOD
NS_NewThread(nsIThread **result,
nsIRunnable *initialEvent = nullptr,
uint32_t stackSize = nsIThreadManager::DEFAULT_STACK_SIZE);
/**
* Creates a named thread, otherwise the same as NS_NewThread
*/
template <size_t LEN>
inline NS_METHOD
NS_NewNamedThread(const char (&name)[LEN],
nsIThread **result,
nsIRunnable *initialEvent = nullptr,
uint32_t stackSize = nsIThreadManager::DEFAULT_STACK_SIZE)
{
nsresult rv = NS_NewThread(result, initialEvent, stackSize);
NS_SetThreadName<LEN>(*result, name);
return rv;
}
/**
* Get a reference to the current thread.
*
* @param result
* The resulting nsIThread object.
*/
extern NS_COM_GLUE NS_METHOD
NS_GetCurrentThread(nsIThread **result);
/**
* Get a reference to the main thread.
*
* @param result
* The resulting nsIThread object.
*/
extern NS_COM_GLUE NS_METHOD
NS_GetMainThread(nsIThread **result);
#if defined(MOZILLA_INTERNAL_API) && defined(XP_WIN)
bool NS_IsMainThread();
#elif defined(MOZILLA_INTERNAL_API) && defined(NS_TLS)
// This is defined in nsThreadManager.cpp and initialized to `Main` for the
// main thread by nsThreadManager::Init.
extern NS_TLS mozilla::threads::ID gTLSThreadID;
inline bool NS_IsMainThread()
{
return gTLSThreadID == mozilla::threads::Main;
}
#else
/**
* Test to see if the current thread is the main thread.
*
* @returns true if the current thread is the main thread, and false
* otherwise.
*/
extern NS_COM_GLUE bool NS_IsMainThread();
#endif
/**
* Dispatch the given event to the current thread.
*
* @param event
* The event to dispatch.
*
* @returns NS_ERROR_INVALID_ARG
* If event is null.
*/
extern NS_COM_GLUE NS_METHOD
NS_DispatchToCurrentThread(nsIRunnable *event);
/**
* Dispatch the given event to the main thread.
*
* @param event
* The event to dispatch.
* @param dispatchFlags
* The flags to pass to the main thread's dispatch method.
*
* @returns NS_ERROR_INVALID_ARG
* If event is null.
*/
extern NS_COM_GLUE NS_METHOD
NS_DispatchToMainThread(nsIRunnable *event,
uint32_t dispatchFlags = NS_DISPATCH_NORMAL);
#ifndef XPCOM_GLUE_AVOID_NSPR
/**
* Process all pending events for the given thread before returning. This
* method simply calls ProcessNextEvent on the thread while HasPendingEvents
* continues to return true and the time spent in NS_ProcessPendingEvents
* does not exceed the given timeout value.
*
* @param thread
* The thread object for which to process pending events. If null, then
* events will be processed for the current thread.
* @param timeout
* The maximum number of milliseconds to spend processing pending events.
* Events are not pre-empted to honor this timeout. Rather, the timeout
* value is simply used to determine whether or not to process another event.
* Pass PR_INTERVAL_NO_TIMEOUT to specify no timeout.
*/
extern NS_COM_GLUE NS_METHOD
NS_ProcessPendingEvents(nsIThread *thread,
PRIntervalTime timeout = PR_INTERVAL_NO_TIMEOUT);
#endif
/**
* Shortcut for nsIThread::HasPendingEvents.
*
* It is an error to call this function when the given thread is not the
* current thread. This function will return false if called from some
* other thread.
*
* @param thread
* The current thread or null.
*
* @returns
* A boolean value that if "true" indicates that there are pending events
* in the current thread's event queue.
*/
extern NS_COM_GLUE bool
NS_HasPendingEvents(nsIThread *thread = nullptr);
/**
* Shortcut for nsIThread::ProcessNextEvent.
*
* It is an error to call this function when the given thread is not the
* current thread. This function will simply return false if called
* from some other thread.
*
* @param thread
* The current thread or null.
* @param mayWait
* A boolean parameter that if "true" indicates that the method may block
* the calling thread to wait for a pending event.
*
* @returns
* A boolean value that if "true" indicates that an event from the current
* thread's event queue was processed.
*/
extern NS_COM_GLUE bool
NS_ProcessNextEvent(nsIThread *thread = nullptr, bool mayWait = true);
//-----------------------------------------------------------------------------
// Helpers that work with nsCOMPtr:
inline already_AddRefed<nsIThread>
do_GetCurrentThread() {
nsIThread *thread = nullptr;
NS_GetCurrentThread(&thread);
return already_AddRefed<nsIThread>(thread);
}
inline already_AddRefed<nsIThread>
do_GetMainThread() {
nsIThread *thread = nullptr;
NS_GetMainThread(&thread);
return already_AddRefed<nsIThread>(thread);
}
//-----------------------------------------------------------------------------
#ifdef MOZILLA_INTERNAL_API
// Fast access to the current thread. Do not release the returned pointer! If
// you want to use this pointer from some other thread, then you will need to
// AddRef it. Otherwise, you should only consider this pointer valid from code
// running on the current thread.
extern NS_COM_GLUE nsIThread *NS_GetCurrentThread();
#endif
//-----------------------------------------------------------------------------
#ifndef XPCOM_GLUE_AVOID_NSPR
#undef IMETHOD_VISIBILITY
#define IMETHOD_VISIBILITY NS_COM_GLUE
// This class is designed to be subclassed.
class NS_COM_GLUE nsRunnable : public nsIRunnable
{
public:
NS_DECL_ISUPPORTS
NS_DECL_NSIRUNNABLE
nsRunnable() {
}
protected:
virtual ~nsRunnable() {
}
};
// This class is designed to be subclassed.
class NS_COM_GLUE nsCancelableRunnable : public nsICancelableRunnable
{
public:
NS_DECL_ISUPPORTS
NS_DECL_NSIRUNNABLE
NS_DECL_NSICANCELABLERUNNABLE
nsCancelableRunnable() {
}
protected:
virtual ~nsCancelableRunnable() {
}
};
#undef IMETHOD_VISIBILITY
#define IMETHOD_VISIBILITY NS_VISIBILITY_HIDDEN
// An event that can be used to call a method on a class. The class type must
// support reference counting. This event supports Revoke for use
// with nsRevocableEventPtr.
template <class ClassType,
typename ReturnType = void,
bool Owning = true>
class nsRunnableMethod : public nsRunnable
{
public:
virtual void Revoke() = 0;
// These ReturnTypeEnforcer classes set up a blacklist for return types that
// we know are not safe. The default ReturnTypeEnforcer compiles just fine but
// already_AddRefed will not.
template <typename OtherReturnType>
class ReturnTypeEnforcer
{
public:
typedef int ReturnTypeIsSafe;
};
template <class T>
class ReturnTypeEnforcer<already_AddRefed<T> >
{
// No ReturnTypeIsSafe makes this illegal!
};
// Make sure this return type is safe.
typedef typename ReturnTypeEnforcer<ReturnType>::ReturnTypeIsSafe check;
};
template <class ClassType, bool Owning>
struct nsRunnableMethodReceiver {
ClassType *mObj;
nsRunnableMethodReceiver(ClassType *obj) : mObj(obj) { NS_IF_ADDREF(mObj); }
~nsRunnableMethodReceiver() { Revoke(); }
void Revoke() { NS_IF_RELEASE(mObj); }
};
template <class ClassType>
struct nsRunnableMethodReceiver<ClassType, false> {
ClassType *mObj;
nsRunnableMethodReceiver(ClassType *obj) : mObj(obj) {}
void Revoke() { mObj = nullptr; }
};
template <typename Method, bool Owning> struct nsRunnableMethodTraits;
template <class C, typename R, bool Owning>
struct nsRunnableMethodTraits<R (C::*)(), Owning> {
typedef C class_type;
typedef R return_type;
typedef nsRunnableMethod<C, R, Owning> base_type;
};
#ifdef HAVE_STDCALL
template <class C, typename R, bool Owning>
struct nsRunnableMethodTraits<R (__stdcall C::*)(), Owning> {
typedef C class_type;
typedef R return_type;
typedef nsRunnableMethod<C, R, Owning> base_type;
};
#endif
template <typename Method, bool Owning>
class nsRunnableMethodImpl
: public nsRunnableMethodTraits<Method, Owning>::base_type
{
typedef typename nsRunnableMethodTraits<Method, Owning>::class_type ClassType;
nsRunnableMethodReceiver<ClassType, Owning> mReceiver;
Method mMethod;
public:
nsRunnableMethodImpl(ClassType *obj,
Method method)
: mReceiver(obj)
, mMethod(method)
{}
NS_IMETHOD Run() {
if (MOZ_LIKELY(mReceiver.mObj))
((*mReceiver.mObj).*mMethod)();
return NS_OK;
}
void Revoke() {
mReceiver.Revoke();
}
};
// Use this template function like so:
//
// nsCOMPtr<nsIRunnable> event =
// NS_NewRunnableMethod(myObject, &MyClass::HandleEvent);
// NS_DispatchToCurrentThread(event);
//
// Statically enforced constraints:
// - myObject must be of (or implicitly convertible to) type MyClass
// - MyClass must defined AddRef and Release methods
//
template<typename PtrType, typename Method>
typename nsRunnableMethodTraits<Method, true>::base_type*
NS_NewRunnableMethod(PtrType ptr, Method method)
{
return new nsRunnableMethodImpl<Method, true>(ptr, method);
}
template<typename PtrType, typename Method>
typename nsRunnableMethodTraits<Method, false>::base_type*
NS_NewNonOwningRunnableMethod(PtrType ptr, Method method)
{
return new nsRunnableMethodImpl<Method, false>(ptr, method);
}
#endif // XPCOM_GLUE_AVOID_NSPR
// This class is designed to be used when you have an event class E that has a
// pointer back to resource class R. If R goes away while E is still pending,
// then it is important to "revoke" E so that it does not try use R after R has
// been destroyed. nsRevocableEventPtr makes it easy for R to manage such
// situations:
//
// class R;
//
// class E : public nsRunnable {
// public:
// void Revoke() {
// mResource = nullptr;
// }
// private:
// R *mResource;
// };
//
// class R {
// public:
// void EventHandled() {
// mEvent.Forget();
// }
// private:
// nsRevocableEventPtr<E> mEvent;
// };
//
// void R::PostEvent() {
// // Make sure any pending event is revoked.
// mEvent->Revoke();
//
// nsCOMPtr<nsIRunnable> event = new E();
// if (NS_SUCCEEDED(NS_DispatchToCurrentThread(event))) {
// // Keep pointer to event so we can revoke it.
// mEvent = event;
// }
// }
//
// NS_IMETHODIMP E::Run() {
// if (!mResource)
// return NS_OK;
// ...
// mResource->EventHandled();
// return NS_OK;
// }
//
template <class T>
class nsRevocableEventPtr {
public:
nsRevocableEventPtr()
: mEvent(nullptr) {
}
~nsRevocableEventPtr() {
Revoke();
}
const nsRevocableEventPtr& operator=(T *event) {
if (mEvent != event) {
Revoke();
mEvent = event;
}
return *this;
}
void Revoke() {
if (mEvent) {
mEvent->Revoke();
mEvent = nullptr;
}
}
void Forget() {
mEvent = nullptr;
}
bool IsPending() {
return mEvent != nullptr;
}
T *get() { return mEvent; }
private:
// Not implemented
nsRevocableEventPtr(const nsRevocableEventPtr&);
nsRevocableEventPtr& operator=(const nsRevocableEventPtr&);
nsRefPtr<T> mEvent;
};
/**
* A simple helper to suffix thread pool name
* with incremental numbers.
*/
class nsThreadPoolNaming
{
public:
nsThreadPoolNaming() : mCounter(0) {}
/**
* Creates and sets next thread name as "<aPoolName> #<n>"
* on the specified thread. If no thread is specified (aThread
* is null) then the name is synchronously set on the current thread.
*/
void SetThreadPoolName(const nsACString & aPoolName,
nsIThread * aThread = nullptr);
private:
volatile uint32_t mCounter;
nsThreadPoolNaming(const nsThreadPoolNaming &) MOZ_DELETE;
void operator=(const nsThreadPoolNaming &) MOZ_DELETE;
};
/**
* Thread priority in most operating systems affect scheduling, not IO. This
* helper is used to set the current thread to low IO priority for the lifetime
* of the created object. You can only use this low priority IO setting within
* the context of the current thread.
*/
class MOZ_STACK_CLASS nsAutoLowPriorityIO
{
public:
nsAutoLowPriorityIO();
~nsAutoLowPriorityIO();
private:
bool lowIOPrioritySet;
#if defined(XP_MACOSX)
int oldPriority;
#endif
};
#endif // nsThreadUtils_h__