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// 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/non_thread_safe.h"
#include "base/tracked.h"
#include "base/tuple.h"
#include "base/weak_ptr.h"
// Task ------------------------------------------------------------------------
//
// A task is a generic runnable thingy, usually used for running code on a
// different thread or for scheduling future tasks off of the message loop.
class Task : public tracked_objects::Tracked {
public:
Task() {}
virtual ~Task() {}
// Tasks are automatically deleted after Run is called.
virtual void Run() = 0;
};
class CancelableTask : public Task {
public:
// Not all tasks support cancellation.
virtual void Cancel() = 0;
};
// Scoped Factories ------------------------------------------------------------
//
// These scoped factory objects can be used by non-refcounted objects to safely
// place tasks in a message loop. Each factory guarantees that the tasks it
// produces will not run after the factory is destroyed. Commonly, factories
// are declared as class members, so the class' tasks will automatically cancel
// when the class instance is destroyed.
//
// Exampe Usage:
//
// class MyClass {
// private:
// // This factory will be used to schedule invocations of SomeMethod.
// ScopedRunnableMethodFactory<MyClass> some_method_factory_;
//
// public:
// // It is safe to suppress warning 4355 here.
// MyClass() : some_method_factory_(this) { }
//
// void SomeMethod() {
// // If this function might be called directly, you might want to revoke
// // any outstanding runnable methods scheduled to call it. If it's not
// // referenced other than by the factory, this is unnecessary.
// some_method_factory_.RevokeAll();
// ...
// }
//
// void ScheduleSomeMethod() {
// // If you'd like to only only have one pending task at a time, test for
// // |empty| before manufacturing another task.
// if (!some_method_factory_.empty())
// return;
//
// // The factories are not thread safe, so always invoke on
// // |MessageLoop::current()|.
// MessageLoop::current()->PostDelayedTask(FROM_HERE,
// some_method_factory_.NewRunnableMethod(&MyClass::SomeMethod),
// kSomeMethodDelayMS);
// }
// };
// A ScopedRunnableMethodFactory creates runnable methods for a specified
// object. This is particularly useful for generating callbacks for
// non-reference counted objects when the factory is a member of the object.
template<class T>
class ScopedRunnableMethodFactory {
public:
explicit ScopedRunnableMethodFactory(T* object) : weak_factory_(object) {
}
template <class Method>
inline Task* NewRunnableMethod(Method method) {
return new RunnableMethod<Method, Tuple0>(
weak_factory_.GetWeakPtr(), method, MakeTuple());
}
template <class Method, class A>
inline Task* NewRunnableMethod(Method method, const A& a) {
return new RunnableMethod<Method, Tuple1<A> >(
weak_factory_.GetWeakPtr(), method, MakeTuple(a));
}
template <class Method, class A, class B>
inline Task* NewRunnableMethod(Method method, const A& a, const B& b) {
return new RunnableMethod<Method, Tuple2<A, B> >(
weak_factory_.GetWeakPtr(), method, MakeTuple(a, b));
}
template <class Method, class A, class B, class C>
inline Task* NewRunnableMethod(Method method,
const A& a,
const B& b,
const C& c) {
return new RunnableMethod<Method, Tuple3<A, B, C> >(
weak_factory_.GetWeakPtr(), method, MakeTuple(a, b, c));
}
template <class Method, class A, class B, class C, class D>
inline Task* NewRunnableMethod(Method method,
const A& a,
const B& b,
const C& c,
const D& d) {
return new RunnableMethod<Method, Tuple4<A, B, C, D> >(
weak_factory_.GetWeakPtr(), method, MakeTuple(a, b, c, d));
}
template <class Method, class A, class B, class C, class D, class E>
inline Task* NewRunnableMethod(Method method,
const A& a,
const B& b,
const C& c,
const D& d,
const E& e) {
return new RunnableMethod<Method, Tuple5<A, B, C, D, E> >(
weak_factory_.GetWeakPtr(), method, MakeTuple(a, b, c, d, e));
}
void RevokeAll() { weak_factory_.InvalidateWeakPtrs(); }
bool empty() const { return !weak_factory_.HasWeakPtrs(); }
protected:
template <class Method, class Params>
class RunnableMethod : public Task {
public:
RunnableMethod(const base::WeakPtr<T>& obj, Method meth, const Params& params)
: obj_(obj),
meth_(meth),
params_(params) {
}
virtual void Run() {
if (obj_)
DispatchToMethod(obj_.get(), meth_, params_);
}
private:
base::WeakPtr<T> obj_;
Method meth_;
Params params_;
DISALLOW_COPY_AND_ASSIGN(RunnableMethod);
};
private:
base::WeakPtrFactory<T> weak_factory_;
};
// General task implementations ------------------------------------------------
// Task to delete an object
template<class T>
class DeleteTask : public CancelableTask {
public:
explicit DeleteTask(T* obj) : obj_(obj) {
}
virtual void Run() {
delete obj_;
}
virtual void Cancel() {
obj_ = NULL;
}
private:
T* obj_;
};
// Task to Release() an object
template<class T>
class ReleaseTask : public CancelableTask {
public:
explicit ReleaseTask(T* obj) : obj_(obj) {
}
virtual void Run() {
if (obj_)
obj_->Release();
}
virtual void Cancel() {
obj_ = NULL;
}
private:
T* 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 {
RunnableMethodTraits() {
#ifndef NDEBUG
origin_thread_id_ = PlatformThread::CurrentId();
#endif
}
~RunnableMethodTraits() {
#ifndef NDEBUG
// If destroyed on a separate thread, then we had better have been using
// thread-safe reference counting!
if (origin_thread_id_ != PlatformThread::CurrentId())
DCHECK(T::ImplementsThreadSafeReferenceCounting());
#endif
}
void RetainCallee(T* obj) {
obj->AddRef();
}
void ReleaseCallee(T* obj) {
obj->Release();
}
private:
#ifndef NDEBUG
PlatformThreadId origin_thread_id_;
#endif
};
// 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(FROM_HERE, NewRunnableMethod(object, &Object::method[, a[, b]])
// PostTask(FROM_HERE, NewRunnableFunction(&function[, a[, b]])
// RunnableMethod and NewRunnableMethod implementation -------------------------
template <class T, class Method, class Params>
class RunnableMethod : public CancelableTask {
public:
RunnableMethod(T* obj, Method meth, const Params& params)
: obj_(obj), meth_(meth), params_(params) {
traits_.RetainCallee(obj_);
}
~RunnableMethod() {
ReleaseCallee();
}
virtual void Run() {
if (obj_)
DispatchToMethod(obj_, meth_, params_);
}
virtual void Cancel() {
ReleaseCallee();
}
private:
void ReleaseCallee() {
if (obj_) {
traits_.ReleaseCallee(obj_);
obj_ = NULL;
}
}
T* obj_;
Method meth_;
Params params_;
RunnableMethodTraits<T> traits_;
};
template <class T, class Method>
inline CancelableTask* NewRunnableMethod(T* object, Method method) {
return new RunnableMethod<T, Method, Tuple0>(object, method, MakeTuple());
}
template <class T, class Method, class A>
inline CancelableTask* NewRunnableMethod(T* object, Method method, const A& a) {
return new RunnableMethod<T, Method, Tuple1<A> >(object,
method,
MakeTuple(a));
}
template <class T, class Method, class A, class B>
inline CancelableTask* NewRunnableMethod(T* object, Method method,
const A& a, const B& b) {
return new RunnableMethod<T, Method, Tuple2<A, B> >(object, method,
MakeTuple(a, b));
}
template <class T, class Method, class A, class B, class C>
inline CancelableTask* NewRunnableMethod(T* object, Method method,
const A& a, const B& b, const C& c) {
return new RunnableMethod<T, Method, Tuple3<A, B, C> >(object, method,
MakeTuple(a, b, c));
}
template <class T, class Method, class A, class B, class C, class D>
inline CancelableTask* NewRunnableMethod(T* object, Method method,
const A& a, const B& b,
const C& c, const D& d) {
return new RunnableMethod<T, Method, Tuple4<A, B, C, D> >(object, method,
MakeTuple(a, b,
c, d));
}
template <class T, class Method, class A, class B, class C, class D, class E>
inline CancelableTask* NewRunnableMethod(T* object, Method method,
const A& a, const B& b,
const C& c, const D& d, const E& e) {
return new RunnableMethod<T,
Method,
Tuple5<A, B, C, D, E> >(object,
method,
MakeTuple(a, b, c, d, e));
}
template <class T, class Method, class A, class B, class C, class D, class E,
class F>
inline CancelableTask* NewRunnableMethod(T* object, Method method,
const A& a, const B& b,
const C& c, const D& d, const E& e,
const F& f) {
return new RunnableMethod<T,
Method,
Tuple6<A, B, C, D, E, F> >(object,
method,
MakeTuple(a, b, c, d, e,
f));
}
template <class T, class Method, class A, class B, class C, class D, class E,
class F, class G>
inline CancelableTask* NewRunnableMethod(T* object, Method method,
const A& a, const B& b,
const C& c, const D& d, const E& e,
const F& f, const G& g) {
return new RunnableMethod<T,
Method,
Tuple7<A, B, C, D, E, F, G> >(object,
method,
MakeTuple(a, b, c, d,
e, f, g));
}
// RunnableFunction and NewRunnableFunction implementation ---------------------
template <class Function, class Params>
class RunnableFunction : public CancelableTask {
public:
RunnableFunction(Function function, const Params& params)
: function_(function), params_(params) {
}
~RunnableFunction() {
}
virtual void Run() {
if (function_)
DispatchToFunction(function_, params_);
}
virtual void Cancel() {
}
private:
Function function_;
Params params_;
};
template <class Function>
inline CancelableTask* NewRunnableFunction(Function function) {
return new RunnableFunction<Function, Tuple0>(function, MakeTuple());
}
template <class Function, class A>
inline CancelableTask* NewRunnableFunction(Function function, const A& a) {
return new RunnableFunction<Function, Tuple1<A> >(function, MakeTuple(a));
}
template <class Function, class A, class B>
inline CancelableTask* NewRunnableFunction(Function function,
const A& a, const B& b) {
return new RunnableFunction<Function, Tuple2<A, B> >(function,
MakeTuple(a, b));
}
template <class Function, class A, class B, class C>
inline CancelableTask* NewRunnableFunction(Function function,
const A& a, const B& b,
const C& c) {
return new RunnableFunction<Function, Tuple3<A, B, C> >(function,
MakeTuple(a, b, c));
}
template <class Function, class A, class B, class C, class D>
inline CancelableTask* NewRunnableFunction(Function function,
const A& a, const B& b,
const C& c, const D& d) {
return new RunnableFunction<Function, Tuple4<A, B, C, D> >(function,
MakeTuple(a, b,
c, d));
}
template <class Function, class A, class B, class C, class D, class E>
inline CancelableTask* NewRunnableFunction(Function function,
const A& a, const B& b,
const C& c, const D& d,
const E& e) {
return new RunnableFunction<Function, Tuple5<A, B, C, D, E> >(function,
MakeTuple(a, b,
c, d,
e));
}
// Callback --------------------------------------------------------------------
//
// A Callback is like a Task but with unbound parameters. It is basically an
// object-oriented function pointer.
//
// Callbacks are designed to work with Tuples. A set of helper functions and
// classes is provided to hide the Tuple details from the consumer. Client
// code will generally work with the CallbackRunner base class, which merely
// provides a Run method and is returned by the New* functions. This allows
// users to not care which type of class implements the callback, only that it
// has a certain number and type of arguments.
//
// The implementation of this is done by CallbackImpl, which inherits
// CallbackStorage to store the data. This allows the storage of the data
// (requiring the class type T) to be hidden from users, who will want to call
// this regardless of the implementor's type T.
//
// Note that callbacks currently have no facility for cancelling or abandoning
// them. We currently handle this at a higher level for cases where this is
// necessary. The pointer in a callback must remain valid until the callback
// is made.
//
// Like Task, the callback executor is responsible for deleting the callback
// pointer once the callback has executed.
//
// Example client usage:
// void Object::DoStuff(int, string);
// Callback2<int, string>::Type* callback =
// NewCallback(obj, &Object::DoStuff);
// callback->Run(5, string("hello"));
// delete callback;
// or, equivalently, using tuples directly:
// CallbackRunner<Tuple2<int, string> >* callback =
// NewCallback(obj, &Object::DoStuff);
// callback->RunWithParams(MakeTuple(5, string("hello")));
//
// There is also a 0-args version that returns a value. Example:
// int Object::GetNextInt();
// CallbackWithReturnValue<int>::Type* callback =
// NewCallbackWithReturnValue(obj, &Object::GetNextInt);
// int next_int = callback->Run();
// delete callback;
// Base for all Callbacks that handles storage of the pointers.
template <class T, typename Method>
class CallbackStorage {
public:
CallbackStorage(T* obj, Method meth) : obj_(obj), meth_(meth) {
}
protected:
T* obj_;
Method meth_;
};
// Interface that is exposed to the consumer, that does the actual calling
// of the method.
template <typename Params>
class CallbackRunner {
public:
typedef Params TupleType;
virtual ~CallbackRunner() {}
virtual void RunWithParams(const Params& params) = 0;
// Convenience functions so callers don't have to deal with Tuples.
inline void Run() {
RunWithParams(Tuple0());
}
template <typename Arg1>
inline void Run(const Arg1& a) {
RunWithParams(Params(a));
}
template <typename Arg1, typename Arg2>
inline void Run(const Arg1& a, const Arg2& b) {
RunWithParams(Params(a, b));
}
template <typename Arg1, typename Arg2, typename Arg3>
inline void Run(const Arg1& a, const Arg2& b, const Arg3& c) {
RunWithParams(Params(a, b, c));
}
template <typename Arg1, typename Arg2, typename Arg3, typename Arg4>
inline void Run(const Arg1& a, const Arg2& b, const Arg3& c, const Arg4& d) {
RunWithParams(Params(a, b, c, d));
}
template <typename Arg1, typename Arg2, typename Arg3,
typename Arg4, typename Arg5>
inline void Run(const Arg1& a, const Arg2& b, const Arg3& c,
const Arg4& d, const Arg5& e) {
RunWithParams(Params(a, b, c, d, e));
}
};
template <class T, typename Method, typename Params>
class CallbackImpl : public CallbackStorage<T, Method>,
public CallbackRunner<Params> {
public:
CallbackImpl(T* obj, Method meth) : CallbackStorage<T, Method>(obj, meth) {
}
virtual void RunWithParams(const Params& params) {
// use "this->" to force C++ to look inside our templatized base class; see
// Effective C++, 3rd Ed, item 43, p210 for details.
DispatchToMethod(this->obj_, this->meth_, params);
}
};
// 0-arg implementation
struct Callback0 {
typedef CallbackRunner<Tuple0> Type;
};
template <class T>
typename Callback0::Type* NewCallback(T* object, void (T::*method)()) {
return new CallbackImpl<T, void (T::*)(), Tuple0 >(object, method);
}
// 1-arg implementation
template <typename Arg1>
struct Callback1 {
typedef CallbackRunner<Tuple1<Arg1> > Type;
};
template <class T, typename Arg1>
typename Callback1<Arg1>::Type* NewCallback(T* object,
void (T::*method)(Arg1)) {
return new CallbackImpl<T, void (T::*)(Arg1), Tuple1<Arg1> >(object, method);
}
// 2-arg implementation
template <typename Arg1, typename Arg2>
struct Callback2 {
typedef CallbackRunner<Tuple2<Arg1, Arg2> > Type;
};
template <class T, typename Arg1, typename Arg2>
typename Callback2<Arg1, Arg2>::Type* NewCallback(
T* object,
void (T::*method)(Arg1, Arg2)) {
return new CallbackImpl<T, void (T::*)(Arg1, Arg2),
Tuple2<Arg1, Arg2> >(object, method);
}
// 3-arg implementation
template <typename Arg1, typename Arg2, typename Arg3>
struct Callback3 {
typedef CallbackRunner<Tuple3<Arg1, Arg2, Arg3> > Type;
};
template <class T, typename Arg1, typename Arg2, typename Arg3>
typename Callback3<Arg1, Arg2, Arg3>::Type* NewCallback(
T* object,
void (T::*method)(Arg1, Arg2, Arg3)) {
return new CallbackImpl<T, void (T::*)(Arg1, Arg2, Arg3),
Tuple3<Arg1, Arg2, Arg3> >(object, method);
}
// 4-arg implementation
template <typename Arg1, typename Arg2, typename Arg3, typename Arg4>
struct Callback4 {
typedef CallbackRunner<Tuple4<Arg1, Arg2, Arg3, Arg4> > Type;
};
template <class T, typename Arg1, typename Arg2, typename Arg3, typename Arg4>
typename Callback4<Arg1, Arg2, Arg3, Arg4>::Type* NewCallback(
T* object,
void (T::*method)(Arg1, Arg2, Arg3, Arg4)) {
return new CallbackImpl<T, void (T::*)(Arg1, Arg2, Arg3, Arg4),
Tuple4<Arg1, Arg2, Arg3, Arg4> >(object, method);
}
// 5-arg implementation
template <typename Arg1, typename Arg2, typename Arg3,
typename Arg4, typename Arg5>
struct Callback5 {
typedef CallbackRunner<Tuple5<Arg1, Arg2, Arg3, Arg4, Arg5> > Type;
};
template <class T, typename Arg1, typename Arg2,
typename Arg3, typename Arg4, typename Arg5>
typename Callback5<Arg1, Arg2, Arg3, Arg4, Arg5>::Type* NewCallback(
T* object,
void (T::*method)(Arg1, Arg2, Arg3, Arg4, Arg5)) {
return new CallbackImpl<T, void (T::*)(Arg1, Arg2, Arg3, Arg4, Arg5),
Tuple5<Arg1, Arg2, Arg3, Arg4, Arg5> >(object, method);
}
// An UnboundMethod is a wrapper for a method where the actual object is
// provided at Run dispatch time.
template <class T, class Method, class Params>
class UnboundMethod {
public:
UnboundMethod(Method m, Params p) : m_(m), p_(p) {}
void Run(T* obj) const {
DispatchToMethod(obj, m_, p_);
}
private:
Method m_;
Params p_;
};
// Return value implementation with no args.
template <typename ReturnValue>
struct CallbackWithReturnValue {
class Type {
public:
virtual ReturnValue Run() = 0;
};
};
template <class T, typename Method, typename ReturnValue>
class CallbackWithReturnValueImpl
: public CallbackStorage<T, Method>,
public CallbackWithReturnValue<ReturnValue>::Type {
public:
CallbackWithReturnValueImpl(T* obj, Method meth)
: CallbackStorage<T, Method>(obj, meth) {}
virtual ReturnValue Run() {
return (this->obj_->*(this->meth_))();
}
};
template <class T, typename ReturnValue>
typename CallbackWithReturnValue<ReturnValue>::Type*
NewCallbackWithReturnValue(T* object, ReturnValue (T::*method)()) {
return new CallbackWithReturnValueImpl<T, ReturnValue (T::*)(), ReturnValue>(
object, method);
}
#endif // BASE_TASK_H_