Convert Little Endian to Big Endian - Not getting expected result-CodePudding

I have a very small code where I am trying to convert a 16 bit number from little endian to big endian format.

The value of number is 0x8000 and after conversion I am expecting it to be as 0x0080 - but I am getting some different value as mentioned below:

#include <iostream>
int main()
{
        int num = 0x8000;
        int swap = (num>>8) | (num<<8);
        std::cout << swap << std::endl;
        return 0;
}

The program outputs 8388736 as value which in hex is 0x800080 - I am not sure what wrong am I doing?

CodePudding user response：

If you do 0x8000 << 8 you'll get 0x800000. If you | that with 0x80 you get the answer you now get. You need to filter away the upper part:

int swap = (num>>8) | (0xFF00 & (num<<8));

Suggestion: Use fixed width types, like uint8_t, uint16_t, uint32_t and uint64_t.