这里我为c线程函数pthread_create()
编写了一个线程包装器。它将允许调用任何对象上的任何方法并将任意数量的参数传递给该方法。 API是:
template <typename T, typename R, typename... ATs>
pthread_t NewThread(T *obj, R (T::*mem)(ATs...), ATs... args);
以下是模板:
template<unsigned int i>
class TupleUnpack
{
public:
template<typename R, typename ...ATs, typename ...T_function_arguments>
inline static R unpack (R (*function) (ATs...),
std::tuple<ATs...> arguments_tuple,
T_function_arguments ...function_arguments)
{
return TupleUnpack<i-1>::unpack (function, arguments_tuple, std::get<i-1> (arguments_tuple), function_arguments...);
}
};
template<>
class TupleUnpack<0>
{
public:
template<typename R, typename ...ATs, typename ...T_function_arguments>
inline static R unpack (R (*function) (ATs...),
std::tuple<ATs...> arguments_tuple,
T_function_arguments ...function_arguments)
{
return function (function_arguments...);
}
};
class CallCaller
{
virtual bool dispatch (void)=0;
};
template<typename T,typename R,typename ...ATs>
class Call : public CallCaller
{
public:
Call (T *obj,R (*function) (ATs...),ATs... arguments) :obj(obj),function (function),tuplearg (arguments...) {}
~Call() {}
bool dispatch (void)
{
return TupleUnpack<sizeof ...(ATs)>::unpack (this->function, this->tuplearg);
}
private:
std::tuple<ATs...> tuplearg;
R (*function) (ATs...);
T *obj;
};
void *test(int d,double sf)
{
std::cout<<"yay my thread runs d="<<d<<" sf="<<sf<<std::endl;
}
template<typename T,typename R,typename ...ATs>
void* stub (void* vp)
{
Call<T,R,ATs...>* call = static_cast<Call<T,R,ATs...>*>(vp);
call->dispatch();
delete call;
pthread_exit (0);
}
template <typename T, typename R, typename... ATs>
pthread_t NewThread(T *ob, R (T::*mem)(ATs...), ATs... args)
{
pthread_t tid;
R (*func) (ATs...);
Call<T,R,ATs...> *task=new Call<T,R,ATs...>(ob,&test,args...);
pthread_create(&tid, nullptr, stub<T,R,ATs...>, task) ;
return tid;
}
以下是CPP文件:
#include <tr1/tuple>
#include <utility>
#include <iostream>
#include <pthread.h>
#include <tuple>
#include <type_traits>
#include <utility>
#include "NewThread.hpp"
class X
{
public:
void *method(int a, double x)
{
std::cout<<"yay my tread runs a="<<a<<" x="<<x<<std::endl;
}
};
int main()
{
X x;
int i;
pthread_t tid = NewThread(&x, &X::method, 1234, 3.14);
pthread_join(tid,NULL);
std::cout<<"Thread Ended "<<tid<<std::endl;
return 0;
}
我试图用参数调用x::method()
。正如您所看到的,我有test()
函数类似于x::method()
,只是为了证明我的线程正在运行。但我希望能够拨打x::method()
。有人可以指导我吗?
在Essence中我的当前输出是:
yay my thread runs d=1234 sf=3.14
Thread Ended 139766222432000
我希望我的输出
yay my thread runs a=1234 x=3.14
Thread Ended 139766222432000
答案 0 :(得分:1)
所以这个
R (*function) (ATs...);
是一个函数指针,但是你需要一个成员函数指针
R (T::*function) (ATs...);
要调用成员函数指针,您需要一个对象,并且必须使用以下语法调用它:
self->*function(function_arguments...);
请注意->*
语法。
因此,我向T* self
添加了TupleUnpack<>::unpack
参数,并使用Call<>::dispatch
成员在obj
中调用了该参数。现在,我可以将test
函数替换为mem
中的NewThread
参数。
这是一个补丁:
diff --git a/NewThread.hpp b/NewThread.hpp
index e121294..768f7d9 100644
--- a/NewThread.hpp
+++ b/NewThread.hpp
@@ -5,12 +5,12 @@ template<unsigned int i>
class TupleUnpack
{
public:
- template<typename R, typename ...ATs, typename ...T_function_arguments>
- inline static R unpack (R (*function) (ATs...),
+ template<typename T, typename R, typename ...ATs, typename ...T_function_arguments>
+ inline static R unpack (T* self, R (T::*function) (ATs...),
std::tuple<ATs...> arguments_tuple,
T_function_arguments ...function_arguments)
{
- return TupleUnpack<i-1>::unpack (function, arguments_tuple, std::get<i-1> (arguments_tuple), function_arguments...);
+ return TupleUnpack<i-1>::unpack (self, function, arguments_tuple, std::get<i-1> (arguments_tuple), function_arguments...);
}
};
@@ -18,12 +18,12 @@ template<>
class TupleUnpack<0>
{
public:
- template<typename R, typename ...ATs, typename ...T_function_arguments>
- inline static R unpack (R (*function) (ATs...),
+ template<typename T, typename R, typename ...ATs, typename ...T_function_arguments>
+ inline static R unpack (T* self, R (T::*function) (ATs...),
std::tuple<ATs...> arguments_tuple,
T_function_arguments ...function_arguments)
{
- return function (function_arguments...);
+ return (self->*function) (function_arguments...);
}
};
class CallCaller
@@ -35,19 +35,17 @@ template<typename T,typename R,typename ...ATs>
class Call : public CallCaller
{
public:
- Call (T *obj,R (*function) (ATs...),ATs... arguments) :obj(obj),function (function),tuplearg (arguments...) {}
+ Call (T *obj,R (T::*function) (ATs...),ATs... arguments) :obj(obj),function (function),tuplearg (arguments...) {}
~Call() {}
bool dispatch (void)
{
- return TupleUnpack<sizeof ...(ATs)>::unpack (this->function, this->tuplearg);
+ return TupleUnpack<sizeof ...(ATs)>::unpack(obj, this->function, this->tuplearg);
}
private:
std::tuple<ATs...> tuplearg;
- R (*function) (ATs...);
+ R (T::*function) (ATs...);
T *obj;
};
@@ -71,8 +69,7 @@ template <typename T, typename R, typename... ATs>
pthread_t NewThread(T *ob, R (T::*mem)(ATs...), ATs... args)
{
pthread_t tid;
- R (*func) (ATs...);
- Call<T,R,ATs...> *task=new Call<T,R,ATs...>(ob,&test,args...);
+ Call<T,R,ATs...> *task=new Call<T,R,ATs...>(ob,mem,args...);
pthread_create(&tid, nullptr, stub<T,R,ATs...>, task) ;