定义可访问位，半字节，字节工会 [英] Define union that can access bits, nibbles, bytes

问题描述

union bits {
   unsigned int a : 1;
    unsigned int b : 2;
    unsigned int c : 3;
    unsigned int d : 4;``
    unsigned char x[2];
    unsigned int z; 
};

假设在32位的联盟，
我需要使用单个位，或一组位，或半字节或字节。有没有办法来定义的结合。

Suppose in a union of 32 bits, i need to use a single bit, or a group of bits, or nibble, or bytes. is there a way to define the union.

推荐答案

您需要位域的联合。如果只是用一个工会所有的领域将指向同一个地方。

You need a union of bitfields. If you just use a union all of your fields will point to the same place.

union{
    struct {
        unsigned int bit1 : 1;
        unsigned int bit2 : 1;
        unsigned int bit3 : 1;
        unsigned int bit4 : 1;
        unsigned int bit5 : 1;
        unsigned int bit6 : 1;
        unsigned int bit7 : 1;
        unsigned int bit8 : 1;
        ...
        unsigned int bit32 : 1;
    };
    struct {
        unsigned int nibble1 : 4;
        unsigned int nibble2 : 4;
        ...
    };
    struct {
        unsigned int byte1 : 8;
        unsigned int byte2 : 8;
        ...
    };
    unsigned int int_value;
}

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