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#pragma once
// Declared only so it can be partially specialized
template <class Signature>
class cFunctionRef;
/** A light-weight, type-erased reference to a function object.
This is similar to a std::function but doesn't copy the function object
which means that mutable function objects will be modified for the caller
but would not be if using a std::function (See #3990 for implications of this).
A cFunctionRef has no empty state but is non-owning and so is safe to call
as long as the referred object is still alive. */
template <class Ret, class... Args>
class cFunctionRef<Ret(Args...)>
{
public:
/** Construct from a function object. */
template <class FunctionObject>
cFunctionRef(FunctionObject && a_FunctionObject)
{
// Store an opaque reference to the object.
m_CallableData = &a_FunctionObject;
// Along with a function that knows how to call the object.
m_CallFunction = &ObjectFunctionCaller<FunctionObject>;
}
/** Call the referenced function object */
Ret operator () (Args... a_Args)
{
return m_CallFunction(m_CallableData, std::forward<Args>(a_Args)...);
}
private:
/** Function that performs the call. */
template <class ObjectType>
static Ret ObjectFunctionCaller(void * a_Callable, Args... a_Args)
{
// Convert opaque reference to the concrete type.
using ObjectPtr = typename std::add_pointer<ObjectType>::type;
auto & Object = *static_cast<ObjectPtr>(a_Callable);
// Forward the call down to the object.
return Object(std::forward<Args>(a_Args)...);
}
using cCallFunction = Ret(*)(void *, Args...);
/** Type erased reference to a callable. */
void * m_CallableData;
/** Function that knows how to call the type erased reference. */
cCallFunction m_CallFunction;
};
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