C++ struct 语法“a : b"是什么意思?意思是 [英] What does C++ struct syntax "a : b" mean

问题描述

如果我有一个 C++ 结构体，定义一个 64 位数据字，例如..

If I have a C++ struct, defining a 64bit data word such as..

struct SMyDataWord
{
    int Name : 40;
    int Colour : 24;
};

: 40 语法是什么意思...这是否意味着前 40 位保留给名称，其余 24 位保留给颜色?

What does the : 40 syntax mean... does it mean that the first 40 bits are reserved for the Name and the remaining 24 bits for the Colour?

这就是它的使用方式，但我以前没有遇到过.

This is how it appears to be being used, but I've not come across it before.

推荐答案

位域，从 C 继承而来.Name 是 40 位宽，Colour 是 24 位宽.因此，您的结构至少有 64 位.在我的系统上，64 位是 8 个字节.

Bitfields, carried over from C. Name is 40 bits wide, Colour is 24 bits wide. Your struct therefore has at least 64 bits. On my system 64 bits would be 8 bytes.

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