C++位操作符总结

 #include <stdio.h>
 #include <memory.h>
 #include <malloc.h>
 #define MaxBinLength 16

 //获取无符号数的二进制，这是我自己写的，更简单的方法可以用bitset代替
 char* getUnsignedBinary(unsigned int num)
 {
     int len = MaxBinLength -;
     char *bin = (char*)malloc((MaxBinLength + )*sizeof(char));
     memset(bin,'',MaxBinLength);
     bin[MaxBinLength] = ;
     while(num/ != ){
         bin[len--] = '' + num%;
         num/=;
     }
     if(num!=)
         bin[len--] = '';
     return bin;
 }

 void flip(unsigned short num)
 {
     printf("位求反,运算符为 ~ ,功能简单,将操作数的每一个二进制位取反\n");
     printf("原值:%6d %s\n",num,getUnsignedBinary(num));
     printf("新值:%6d %s\n",~num,getUnsignedBinary(~num));
     printf("-------------------------\n");
 }

 void left_shift(unsigned short num,unsigned short offset)
 {
     printf("左移运算,运算符为 << ,将操作数的二进制位向左移动指定的offset(%d)位数,offset必须小于原数的位数,右边新加的位以0填充\n",offset);
     printf("原值:%6d %s\n",num,getUnsignedBinary(num));
     printf("新值:%6d %s\n",num<<offset,getUnsignedBinary(num<<offset));
     printf("-------------------------\n");
 }

 void right_shift(unsigned short num,unsigned short offset)
 {
     printf("右移运算,运算符为 >> ,将操作数的二进制位向右移动指定的offset(%d)位数,offset必须小于原数的位数,\n\
 如果操作数无符号,左边新加的位以0填充,如果操作数有符号,右边新加的位可能以符号位填充，也可能以0填充,\n\
 具体依赖于机器,见注释\n",offset);
     printf("原值:%6d %s\n",num,getUnsignedBinary(num));
     printf("新值:%6d %s\n",num>>offset,getUnsignedBinary(num>>offset));
     printf("-------------------------\n");
 }

 void weiyu(unsigned short num,unsigned short num_1)
 {
     printf("位与,运算符为 & ,对两个操作数的每一个对应二进制位进行'与'运算,运算方式类似于&&运算\n");
     printf("原值:%6d %s\n",num,getUnsignedBinary(num));
     printf("原值:%6d %s\n",num_1,getUnsignedBinary(num_1));
     printf("新值:%6d %s\n",num&num_1,getUnsignedBinary(num&num_1));
     printf("-------------------------\n");
 }

 void weihuo(unsigned short num,unsigned short num_1)
 {
     printf("位或,运算符为 | ,对两个操作数的每一个对应二进制位进行'或'运算,运算方式类似于||运算\n");
     printf("原值:%6d %s\n",num,getUnsignedBinary(num));
     printf("原值:%6d %s\n",num_1,getUnsignedBinary(num_1));
     printf("新值:%6d %s\n",num|num_1,getUnsignedBinary(num|num_1));
     printf("-------------------------\n");
 }

 void weiyihuo(unsigned short num,unsigned short num_1)
 {
     printf("位异或,运算符为 ^ ,对两个操作数的每一个对应二进制位进行'异或'运算,两个位不同则为1，相同则为0\n");
     printf("原值:%6d %s\n",num,getUnsignedBinary(num));
     printf("原值:%6d %s\n",num_1,getUnsignedBinary(num_1));
     printf("新值:%6d %s\n",num^num_1,getUnsignedBinary(num^num_1));
     printf("-------------------------\n");
 }

 void zhushi()
 {
     printf("注释:位操作符只能操作整数,这个整数可以是有符号的也可以是无符号的,\n\
 如果操作数为负数,则位如何处理其符号位依赖于机器,所以在一个环境中实现的\n\
 程序可能无法用于另一环境，因此强烈建议使用unsigned整数作为操作数\n\
 参考<<C++primer>>(人民邮电出版社第4版)155页\n");
     printf("-------------------------\n");
 }

 int main()
 {
     unsigned short num = ,num_1 = ,offset = ;
     flip(num);
     left_shift(num,offset);
     right_shift(num,offset);
     weiyu(num,num_1);
     weihuo(num,num_1);
     weiyihuo(num,num_1);
     zhushi();
     return ;
 }

后来又自己试了一下，当在左移运算中，offset是可以大于操作数的长度的。当offset大一操作数长度的时候，操作的结果会自动更改整数类型，以容纳更多的位数,例如unsigned char可以变为short，short可以变为int等。

而右移运算中，无论offset为何值,操作结果的长度不会发证变化。

看demo，只是经过简单的验证。

 #include <bitset>
 #include <iostream>
 #include <iomanip>
 using namespace std;

 #define uint8_t unsigned char
 #define uint16_t unsigned short
 #define uint32_t unsigned int

 bitset<> getBinary32(int num)
 {
     bitset<> bit(num);
     return bit;
 }

 bitset<> getBinary8(uint8_t num)
 {
     bitset<> bit(num);
     return bit;
 }

 int main()
 {
     uint8_t a = ;
     //左移
     cout<<"左移"<<endl<<"a="<<(int)a<<" "<<getBinary8(a)<<endl;
     for(int i = ;i<=;i++)
     {
         if(i < )
         {
             uint16_t b = a<<i;
             cout<<"b="<<setw()<<(unsigned short)b<<" "<<getBinary32(b)<<endl;
         }
         else
         {
             uint32_t b = a<<i;
             cout<<"b="<<setw()<<(unsigned int)b<<" "<<getBinary32(b)<<endl;
         }
     }

     //右移
     cout<<"右移"<<endl<<"a="<<(int)a<<" "<<getBinary8(a)<<endl;
     for(i = ;i<=;i++)
     {
         if(i < )
         {
             uint16_t b = a>>i;
             cout<<"b="<<setw()<<(unsigned short)b<<" "<<getBinary32(b)<<endl;
         }
         else
         {
             uint32_t b = a>>i;
             cout<<"b="<<setw()<<(unsigned int)b<<" "<<getBinary32(b)<<endl;
         }
     }
     return ;
 }