Typedef有两组括号？ [英] Typedef with two sets of brackets?

问题描述

我遇到一个typedef在一些代码，这是：

I have come across a typedef in some code which is this:

typedef void (NE_API *NeWindowProcCallback)(void* hWnd, NEuint uMsgId, NEuint wParam, NEuint64 lParam);

然而，我不熟悉这种语法。

however, I am unfamiliar with this syntax. can anyone explain this?

此外，如果我跳转到NE_API的声明，我发现这个：

Also, if I jump to the declaration of NE_API, I find this:

#   define NE_API __stdcall

我认为这可能与答案，并对此的解释也将非常感谢。谢谢。

I thought this may be relevant to the answer, and an explanation of this also would be very appreciated. Thank you.

推荐答案

这是函数指针的typedef，函数返回 void ，具有 __ stdcall 调用约定，并接受四个参数。因此，您可以将任何具有此签名的函数的地址分配给 NeWindowProcCallback 类型的变量。然后，这个变量可以作为参数传递给需要回调函数的其他函数。有关如何使用函数指针的更多详细信息，请参见此。

That is the typedef of a function pointer for which the function which returns void, has __stdcall calling convention, and accepts four parameters. So you can assign the address of any function which has this signature to a variable of type NeWindowProcCallback. This variable can then be passed as a parameter to other functions which expect a callback function. See this for more details on how function pointers can be used.

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