blob: 753d540a79a494a3c13d33a696193f9ec1625ec9 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
|
#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.
### Usage
`cFunctionRef` is used whenever you call a normal function with a lambda. e.g.
one of the `cWorld::DoWith` functions,
m_World->DoWithChunkAt(BlockPos, [](cChunk & a_Chunk) -> bool
{
...
}
);
It looks like you're calling it with a lambda but that would require
`DoWithChunkAt` to be a template. The function is really being called with
`cFunctionRef<bool(cChunk&)>` which is constructed from the lambda via a
templated constructor. This gives you a generic pointer to the lambda which
doesn't depend on the type of the function object it references.
### Notes
- This is similar to a `std::function` but doesn't copy the function object.
This 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,
typename std::enable_if< // Don't disable the default copy constructor
!std::is_same<typename std::decay<FunctionObject>::type, cFunctionRef>::value,
int>::type = 0
>
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;
};
|
