C++工作笔记-3种方法对数据类型进行拆分（可用于各种协议）(long int short)

比如用Long Long存3个数据的内容。

这里要知道大小端的知识点。

方法一是用位运算；

方法二是用指针；

方法三是结构体（本质上也是指针）；

运行截图如下：

源码如下：

main.cpp

#include <iostream>
using namespace std;
 
struct SplitLongLong{
    short shortValue2;
    short shortValue1;
    int intValue;
};
 
void main(){
 
    long long myTestLongLong=1234605616436508552;
    cout<<"hexadecimal original data: "<<hex<<"0x:"<<myTestLongLong<<endl;
    cout<<"decimalism original data:"<<dec<<myTestLongLong<<endl<<endl;
 
    //The first method!    
    cout<<"The first method!"<<endl;
    int method1_int=(int)(myTestLongLong>>4*8);        //Little-endian
    short method1_short1=(short)(myTestLongLong>>2*8);
    short method1_short2=(short)(myTestLongLong);
 
    cout<<"hexadecimal 0x"<<hex<<method1_int<<"   0x"<<method1_short1<<"   0x"<<method1_short2<<endl;
    cout<<"decimalism "<<dec<<method1_int<<"  "<<method1_short1<<"  "<<method1_short2<<endl<<endl;
 
    long long method1_long=((long long)method1_int<<4*8)+((long long)method1_short1<<2*8)+((long long)method1_short2);
    cout<<"hexadecimal combined data :0x"<<hex<<method1_long<<endl;
    cout<<"decimalism combined data :"<<dec<<method1_long<<endl<<endl;
 
    //The second method!
    cout<<"The second method!"<<endl;
    char *ptr=(char *)(&myTestLongLong);
    int method2_int = *(int *)(ptr+4);        //Little-endian
    short method2_short1 = *(short*)(ptr+2);
    short method2_short2 = *(short*)ptr;
    cout<<"hexadecimal 0x"<<hex<<method2_int<<"  0x"<<method2_short1<<"  0x"<<method2_short2<<endl;
    cout<<"decimalism "<<dec<<method2_int<<"  "<<method2_short1<<"  "<<method2_short2<<endl<<endl;
 
    long long method2_long;
    ptr=(char*)(&method2_long);
    *(short*)ptr=method2_short2;
    *(short*)(ptr+2)=method2_short1;
    *(int*)(ptr+4)=method2_int;
    cout<<"hexadecimal combined data :0x"<<hex<<method2_long<<endl;
    cout<<"decimalism combined data :"<<dec<<method2_long<<endl<<endl;
 
 
 
    //The third method!
    cout<<"The third method!"<<endl;
    SplitLongLong split;
    split=*(SplitLongLong*)&myTestLongLong;
    cout<<"hexadecimal 0x"<<hex<<split.intValue<<"  0x"<<split.shortValue1<<"  0x"<<split.shortValue2<<endl;
    cout<<"decimalism "<<dec<<split.intValue<<"  "<<split.shortValue1<<"  "<<split.shortValue2<<endl<<endl;
 
    long long method3_long;
    ptr=(char*)(&method3_long);
    *(short*)ptr=split.shortValue2;
    *(short*)(ptr+2)=split.shortValue1;
    *(int*)(ptr+4)=split.intValue;
    cout<<"hexadecimal combined data :0x"<<hex<<method3_long<<endl;
    cout<<"decimalism combined data :"<<dec<<method3_long<<endl<<endl;
 
    getchar();
}