C/C++ int数与多枚举值互转的实现

在C/C++在C/C++的开发中经常会遇到各种数据类型互转的情况，正常的互转有：单个枚举转int数，int数转float数，float数转double数等。但是我们有时也会遇到多个枚举值与数字互转的情形（例如多个算法类型枚举开启标志转成数字，这个数字来表示多个标志位，按位来表示）。这样一个数字就能表示很多个标志位了，针对内存较少的嵌入式设备，这么操作可以达到节约内存消耗，提高程序运行效率的目的。

Demo示例

demo核心知识点：通过位运算符（布尔位运算符："~"、"&"、"|"；移位运算符："<<"）实现int数与多枚举值互转。

Code:

#include <iostream>

using namespace std;


int nFlag = 0; //用移位表示各个枚举的开关
typedef enum
{
    TYPEA, //A开启，则nflag为1=0x00000001
    TYPEB, //B开启，则nflag为2=0x00000010
    TYPEC, //C开启，则nflag为4=0x00000100
    TYPED, //D开启，则nflag为8=0x00001000
    TYPENUM //枚举最大值，计数用
}EMTypeNum;

void int2enum (int n)
{
    if(n&(0x01<<TYPEA))
    {
     //为真
     cout << "TYPEA is ON\n";
    }
    else
    {
     //为假
     cout << "TYPEA is OFF\n";
    }
    
    if(n&(0x01<<TYPEB))
    {
     //为真
     cout << "TYPEB is ON\n";
    }
    else
    {
     //为假
     cout << "TYPEB is OFF\n";
    }
    
    if(n&(0x01<<TYPEC))
    {
     //为真
     cout << "TYPEC is ON\n";
    }
    else
    {
     //为假
     cout << "TYPEC is OFF\n";
    }

    if(n&(0x01<<TYPED))
    {
     //为真
     cout << "TYPED is ON\n";
    }
    else
    {
     //为假
     cout << "TYPED is OFF\n";
    }      
} 

void enum2int(EMTypeNum eMType, bool bOn)
{
    if(bOn)
    {
        nFlag |= (0x01 << eMType);
    }
    else
    {
        nFlag &= ~(0x01 << eMType);
    }
    cout << "nFlag:" << nFlag << endl;
}

int main() {

    int i = 0;
    for(i = 0; i < TYPENUM;i++)
    {
        enum2int((EMTypeNum)i, true);
        int2enum(nFlag);
        cout << endl;
    }
    
    
    for(i = 0; i < TYPENUM;i++)
    {
        enum2int((EMTypeNum)i, false);
        int2enum(nFlag); 
        cout << endl;
    }
    
    return 0;
}

Result:

nFlag:1
TYPEA is ON
TYPEB is OFF
TYPEC is OFF
TYPED is OFF

nFlag:3
TYPEA is ON
TYPEB is ON
TYPEC is OFF
TYPED is OFF

nFlag:7
TYPEA is ON
TYPEB is ON
TYPEC is ON
TYPED is OFF

nFlag:15
TYPEA is ON
TYPEB is ON
TYPEC is ON
TYPED is ON

nFlag:14
TYPEA is OFF
TYPEB is ON
TYPEC is ON
TYPED is ON

nFlag:12
TYPEA is OFF
TYPEB is OFF
TYPEC is ON
TYPED is ON

nFlag:8
TYPEA is OFF
TYPEB is OFF
TYPEC is OFF
TYPED is ON

nFlag:0
TYPEA is OFF
TYPEB is OFF
TYPEC is OFF
TYPED is OFF

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