gecko/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: */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla code.
*
* The Initial Developer of the Original Code is Google Inc.
* Portions created by the Initial Developer are Copyright (C) 2006
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Darin Fisher <darin@meer.net>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef nsThreadUtils_h__
#define nsThreadUtils_h__
#include "prthread.h"
#include "prinrval.h"
#include "nsIThreadManager.h"
#include "nsIThread.h"
#include "nsIRunnable.h"
#include "nsStringGlue.h"
#include "nsCOMPtr.h"
// This is needed on some systems to prevent collisions between the symbols
// appearing in xpcom_core and xpcomglue. It may be unnecessary in the future
// with better toolchain support.
#ifdef MOZILLA_INTERNAL_API
# define NS_NewThread NS_NewThread_P
# define NS_GetCurrentThread NS_GetCurrentThread_P
# define NS_GetMainThread NS_GetMainThread_P
# define NS_IsMainThread NS_IsMainThread_P
# define NS_DispatchToCurrentThread NS_DispatchToCurrentThread_P
# define NS_DispatchToMainThread NS_DispatchToMainThread_P
# define NS_ProcessPendingEvents NS_ProcessPendingEvents_P
# define NS_HasPendingEvents NS_HasPendingEvents_P
# define NS_ProcessNextEvent NS_ProcessNextEvent_P
#endif
//-----------------------------------------------------------------------------
// These methods are alternatives to the methods on nsIThreadManager, provided
// for convenience.
/**
* 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.
*
* @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 = nsnull);
/**
* 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)
NS_COM bool NS_IsMainThread();
#elif defined(MOZILLA_INTERNAL_API) && defined(NS_TLS)
// This is defined in nsThreadManager.cpp and initialized to `true` for the
// main thread by nsThreadManager::Init.
extern NS_TLS bool gTLSIsMainThread;
#ifdef MOZ_ENABLE_LIBXUL
inline bool NS_IsMainThread()
{
return gTLSIsMainThread;
}
#else
NS_COM bool NS_IsMainThread();
#endif
#else
/**
* Test to see if the current thread is the main thread.
*
* @returns PR_TRUE if the current thread is the main thread, and PR_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,
PRUint32 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 PR_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 PRBool
NS_HasPendingEvents(nsIThread *thread = nsnull);
/**
* 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 PR_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 PRBool
NS_ProcessNextEvent(nsIThread *thread = nsnull, PRBool mayWait = PR_TRUE);
//-----------------------------------------------------------------------------
// Helpers that work with nsCOMPtr:
inline already_AddRefed<nsIThread>
do_GetCurrentThread() {
nsIThread *thread = nsnull;
NS_GetCurrentThread(&thread);
return already_AddRefed<nsIThread>(thread);
}
inline already_AddRefed<nsIThread>
do_GetMainThread() {
nsIThread *thread = nsnull;
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() {
}
};
#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>
class nsRunnableMethod : public nsRunnable
{
public:
typedef ReturnType (ClassType::*Method)();
nsRunnableMethod(ClassType *obj, Method method)
: mObj(obj), mMethod(method) {
NS_ADDREF(mObj);
}
NS_IMETHOD Run() {
if (!mObj)
return NS_OK;
(mObj->*mMethod)();
return NS_OK;
}
void Revoke() {
NS_IF_RELEASE(mObj);
}
// 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;
protected:
virtual ~nsRunnableMethod() {
NS_IF_RELEASE(mObj);
}
private:
ClassType* mObj;
Method mMethod;
};
// Use this helper macro like so:
//
// nsCOMPtr<nsIRunnable> event =
// NS_NEW_RUNNABLE_METHOD(MyClass, myObject, HandleEvent);
// NS_DispatchToCurrentThread(event);
//
// Constraints:
// - myObject must be of type MyClass
// - MyClass must defined AddRef and Release methods
//
// NOTE: Attempts to make this a template function caused VC6 to barf :-(
//
#define NS_NEW_RUNNABLE_METHOD(class_, obj_, method_) \
ns_new_runnable_method(obj_, &class_::method_)
template<class ClassType, typename ReturnType>
nsRunnableMethod<ClassType, ReturnType>*
ns_new_runnable_method(ClassType* obj, ReturnType (ClassType::*method)())
{
return new nsRunnableMethod<ClassType, ReturnType>(obj, method);
}
// An event that can be used to call a method on a class, but holds only
// a raw pointer to the object on which the method will be called. This
// event supports Revoke for use with nsRevocableEventPtr and should
// almost always be used with it.
template <class ClassType, typename ReturnType = void>
class nsNonOwningRunnableMethod : public nsRunnable
{
public:
typedef ReturnType (ClassType::*Method)();
nsNonOwningRunnableMethod(ClassType *obj, Method method)
: mObj(obj), mMethod(method) {
}
NS_IMETHOD Run() {
if (!mObj)
return NS_OK;
(mObj->*mMethod)();
return NS_OK;
}
void Revoke() {
mObj = nsnull;
}
// 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;
protected:
virtual ~nsNonOwningRunnableMethod() {
}
private:
ClassType* mObj;
Method mMethod;
};
#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 = nsnull;
// }
// 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(nsnull) {
}
~nsRevocableEventPtr() {
Revoke();
}
const nsRevocableEventPtr& operator=(T *event) {
Revoke();
mEvent = event;
return *this;
}
void Revoke() {
if (mEvent) {
mEvent->Revoke();
mEvent = nsnull;
}
}
void Forget() {
mEvent = nsnull;
}
PRBool IsPending() {
return mEvent != nsnull;
}
T *get() { return mEvent; }
private:
// Not implemented
nsRevocableEventPtr(const nsRevocableEventPtr&);
nsRevocableEventPtr& operator=(const nsRevocableEventPtr&);
T *mEvent;
};
#endif // nsThreadUtils_h__