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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: */
// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_TASK_H_
#define BASE_TASK_H_
#include "base/revocable_store.h"
#include "base/tuple.h"
#include "nsISupportsImpl.h"
#include "nsThreadUtils.h"
#include <type_traits>
#include <utility>
// Helper functions so that we can call a function a pass it arguments that come
// from a Tuple.
namespace details {
// Call the given method on the given object. Arguments are passed by move
// semantics from the given tuple. If the tuple has length N, the sequence must
// be IndexSequence<0, 1, ..., N-1>.
template <size_t... Indices, class ObjT, class Method, typename... Args>
void CallMethod(std::index_sequence<Indices...>, ObjT* obj, Method method,
std::tuple<Args...>& arg) {
(obj->*method)(std::move(std::get<Indices>(arg))...);
}
// Same as above, but call a function.
template <size_t... Indices, typename Function, typename... Args>
void CallFunction(std::index_sequence<Indices...>, Function function,
std::tuple<Args...>& arg) {
(*function)(std::move(std::get<Indices>(arg))...);
}
} // namespace details
// Call a method on the given object. Arguments are passed by move semantics
// from the given tuple.
template <class ObjT, class Method, typename... Args>
void DispatchTupleToMethod(ObjT* obj, Method method, std::tuple<Args...>& arg) {
details::CallMethod(std::index_sequence_for<Args...>{}, obj, method, arg);
}
// Same as above, but call a function.
template <typename Function, typename... Args>
void DispatchTupleToFunction(Function function, std::tuple<Args...>& arg) {
details::CallFunction(std::index_sequence_for<Args...>{}, function, arg);
}
// General task implementations ------------------------------------------------
// Task to delete an object
template <class T>
class DeleteTask : public mozilla::CancelableRunnable {
public:
explicit DeleteTask(T* obj)
: mozilla::CancelableRunnable("DeleteTask"), obj_(obj) {}
NS_IMETHOD Run() override {
delete obj_;
return NS_OK;
}
virtual nsresult Cancel() override {
obj_ = NULL;
return NS_OK;
}
private:
T* MOZ_UNSAFE_REF(
"The validity of this pointer must be enforced by "
"external factors.") obj_;
};
// RunnableMethodTraits --------------------------------------------------------
//
// This traits-class is used by RunnableMethod to manage the lifetime of the
// callee object. By default, it is assumed that the callee supports AddRef
// and Release methods. A particular class can specialize this template to
// define other lifetime management. For example, if the callee is known to
// live longer than the RunnableMethod object, then a RunnableMethodTraits
// struct could be defined with empty RetainCallee and ReleaseCallee methods.
template <class T>
struct RunnableMethodTraits {
static void RetainCallee(T* obj) { obj->AddRef(); }
static void ReleaseCallee(T* obj) { obj->Release(); }
};
// This allows using the NewRunnableMethod() functions with a const pointer
// to the callee object. See the similar support in nsRefPtr for a rationale
// of why this is reasonable.
template <class T>
struct RunnableMethodTraits<const T> {
static void RetainCallee(const T* obj) { const_cast<T*>(obj)->AddRef(); }
static void ReleaseCallee(const T* obj) { const_cast<T*>(obj)->Release(); }
};
// RunnableMethod and RunnableFunction -----------------------------------------
//
// Runnable methods are a type of task that call a function on an object when
// they are run. We implement both an object and a set of NewRunnableMethod and
// NewRunnableFunction functions for convenience. These functions are
// overloaded and will infer the template types, simplifying calling code.
//
// The template definitions all use the following names:
// T - the class type of the object you're supplying
// this is not needed for the Static version of the call
// Method/Function - the signature of a pointer to the method or function you
// want to call
// Param - the parameter(s) to the method, possibly packed as a Tuple
// A - the first parameter (if any) to the method
// B - the second parameter (if any) to the mathod
//
// Put these all together and you get an object that can call a method whose
// signature is:
// R T::MyFunction([A[, B]])
//
// Usage:
// PostTask(NewRunnableMethod(object, &Object::method[, a[, b]])
// PostTask(NewRunnableFunction(&function[, a[, b]])
// RunnableMethod and NewRunnableMethod implementation -------------------------
template <class T, class Method, class Params>
class RunnableMethod : public mozilla::CancelableRunnable,
public RunnableMethodTraits<T> {
public:
RunnableMethod(T* obj, Method meth, Params&& params)
: mozilla::CancelableRunnable("RunnableMethod"),
obj_(obj),
meth_(meth),
params_(std::forward<Params>(params)) {
this->RetainCallee(obj_);
}
~RunnableMethod() { ReleaseCallee(); }
NS_IMETHOD Run() override {
if (obj_) DispatchTupleToMethod(obj_, meth_, params_);
return NS_OK;
}
virtual nsresult Cancel() override {
ReleaseCallee();
return NS_OK;
}
private:
void ReleaseCallee() {
if (obj_) {
RunnableMethodTraits<T>::ReleaseCallee(obj_);
obj_ = nullptr;
}
}
// This is owning because of the RetainCallee and ReleaseCallee calls in the
// constructor and destructor.
T* MOZ_OWNING_REF obj_;
Method meth_;
Params params_;
};
namespace dont_add_new_uses_of_this {
// Don't add new uses of this!!!!
template <class T, class Method, typename... Args>
inline already_AddRefed<mozilla::Runnable> NewRunnableMethod(T* object,
Method method,
Args&&... args) {
typedef std::tuple<std::decay_t<Args>...> ArgsTuple;
RefPtr<mozilla::Runnable> t = new RunnableMethod<T, Method, ArgsTuple>(
object, method, std::make_tuple(std::forward<Args>(args)...));
return t.forget();
}
} // namespace dont_add_new_uses_of_this
// RunnableFunction and NewRunnableFunction implementation ---------------------
template <class Function, class Params>
class RunnableFunction : public mozilla::CancelableRunnable {
public:
RunnableFunction(const char* name, Function function, Params&& params)
: mozilla::CancelableRunnable(name),
function_(function),
params_(std::forward<Params>(params)) {}
~RunnableFunction() {}
NS_IMETHOD Run() override {
if (function_) DispatchTupleToFunction(function_, params_);
return NS_OK;
}
virtual nsresult Cancel() override {
function_ = nullptr;
return NS_OK;
}
Function function_;
Params params_;
};
template <class Function, typename... Args>
inline already_AddRefed<mozilla::CancelableRunnable>
NewCancelableRunnableFunction(const char* name, Function function,
Args&&... args) {
typedef std::tuple<std::decay_t<Args>...> ArgsTuple;
RefPtr<mozilla::CancelableRunnable> t =
new RunnableFunction<Function, ArgsTuple>(
name, function, std::make_tuple(std::forward<Args>(args)...));
return t.forget();
}
template <class Function, typename... Args>
inline already_AddRefed<mozilla::Runnable> NewRunnableFunction(
const char* name, Function function, Args&&... args) {
typedef std::tuple<std::decay_t<Args>...> ArgsTuple;
RefPtr<mozilla::Runnable> t = new RunnableFunction<Function, ArgsTuple>(
name, function, std::make_tuple(std::forward<Args>(args)...));
return t.forget();
}
#endif // BASE_TASK_H_