如何获得用户定义结构的大小? (大小) [英] How to get the size of a user defined struct? (sizeof)

问题描述

我有一个带有C表示的结构:

I've got a structure with C representation:

struct Scard_IO_Request {
    proto: u32,
    pciLength: u32
}

当我想使用以下命令询问sizeof时(如C sizeof()中的情况):

when I want to ask the sizeof (like in C sizeof()) using:

mem::sizeof<Scard_IO_Request>();

我收到编译错误:

"error: `sizeof` is a reserved keyword"

为什么不能像在C中那样使用此sizeof函数?有其他选择吗?

Why can't I use this sizeof function like in C? Is there an alternative?

推荐答案

有两个原因:

1. 没有像sizeof这样的功能，因此编译器将很难调用它.

1. There is no such function as "sizeof", so the compiler is going to have a rather difficult time calling it.

那不是您调用通用函数的方式.

That's not how you invoke generic functions.

如果您查看mem::size_of的文档(即使您搜索"sizeof"，也可以找到该文档) )，您会看到它包含一个可运行示例告诉您如何调用它.对于后代，有问题的示例是:

If you check the documentation for mem::size_of (which you can find even if you search for "sizeof"), you will see that it includes a runnable example which shows you how to call it. For posterity, the example in question is:

fn main() {
    use std::mem;
    assert_eq!(4, mem::size_of::<i32>());
}

在您的特定情况下，您将使用来获得该结构的大小

In your specific case, you'd get the size of that structure using

mem::size_of::<Scard_IO_Request>()

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