Converting an int to a 2 byte hex value in C

Question

I need to convert an int to a 2 byte hex value to store in a char array, in C. How can I do this?

Answer 1

If you're allowed to use library functions:

int x = SOME_INTEGER; char res[5]; /* two bytes of hex = 4 characters, plus NULL terminator */  if (x <= 0xFFFF) {     sprintf(&res[0], "%04x", x); } 

Your integer may contain more than four hex digits worth of data, hence the check first.

If you're not allowed to use library functions, divide it down into nybbles manually:

#define TO_HEX(i) (i <= 9 ? '0' + i : 'A' - 10 + i)  int x = SOME_INTEGER; char res[5];  if (x <= 0xFFFF) {     res[0] = TO_HEX(((x & 0xF000) >> 12));        res[1] = TO_HEX(((x & 0x0F00) >> 8));     res[2] = TO_HEX(((x & 0x00F0) >> 4));     res[3] = TO_HEX((x & 0x000F));     res[4] = '\0'; }