如何在类c++中压缩一个结构？

#include <iostream>

#pragma pack(push, 1) // 设置字节对齐为1字节

class CompressedStruct {
public:
    unsigned int field1 : 4; // 使用4位存储field1
    unsigned int field2 : 8; // 使用8位存储field2
    unsigned int field3 : 2; // 使用2位存储field3
};

#pragma pack(pop) // 恢复默认字节对齐

int main() {
    CompressedStruct obj;
    obj.field1 = 7;
    obj.field2 = 255;
    obj.field3 = 1;

    std::cout << "Size of CompressedStruct: " << sizeof(obj) << " bytes" << std::endl;
    std::cout << "field1: " << obj.field1 << std::endl;
    std::cout << "field2: " << obj.field2 << std::endl;
    std::cout << "field3: " << obj.field3 << std::endl;

    return 0;
}

Size of CompressedStruct: 1 bytes
field1: 7
field2: 255
field3: 1