c++ - Bit shifting in hexadecimal in visual studio and outputting through cout -


i trying learn c++ following tutorial online. tutorial showing me how make program using sdl2 , got lost on 1 of tutorials involving bit shifting in hex. lecturer using eclipse ide while i'm using visual studio community 2017. i'm trying "cout" output this: ff123456 using code demonstrated in tutorial.

#include <iostream> #include <string> #include <iomanip> using namespace std;  int main() { //0xff123456 want resulting hexadecimal below 1 here using unsigned chars , build sequentially byte after byte  unsigned char alpha = 0xff; unsigned char red = 0x12; unsigned char blue = 0x34; unsigned char green = 0x56;  unsigned char color = alpha;  color += alpha; color <<= 8; //moves values in color 8 bits left  color += red; color <<= 8; color += blue; color <<= 8; color <<= green;   cout << setfill('0') << setw(8) << hex << color << endl;  return 0; }

however, every time run program, cout display "0000000" instead of ff123456. there i'm doing wrong or missing here?

your color unsigned char, stands 1 byte, not four. hence, every shift <<= 8 erase assigned before. use unsigned int or, better, uint32_t-type color. further, initialize color value of alpha, , add alpha second time. suggest initialize color 0:

uint32_t color = 0;  color += alpha; color <<= 8; //moves values in color 8 bits left color += red; color <<= 8; color += blue; color <<= 8; color += green;  cout << setfill('0') << std::uppercase << setw(8) << hex << color << endl;

output:

ff123456

btw: fixed typo, changed color <<= green color += green. and, ge ff123456 instead of ff123456, added std::uppercase.


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