OSDev.org

Code: Select all

void IntToHex(unsigned int number, char *buffer) {
  for (int i = 0; i<sizeof(unsigned int) * 2; i++) {
    buffer[i] = ((number >> (4*i)) & 0xF) + '0';
    if (buffer[i] > '9') buffer[i] += 'A' - '9';
  }
  buffer[i] = '\0';
}

Code: Select all

#include <stdio.h>

const char *CharRep = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

unsigned int HexToInt(const char *Hex)
{
    //Assuming the "0x" prefix has been cut off by the caller
    unsigned int RetVal = 0;
    int i;

    while(*Hex != '\0')  //Loop until end of Hex Number String
    {
        for(i = 0 ; CharRep[i] != '\0' ; ++i)  //Loop through the number representations
        {
            if( CharRep[i] == *Hex ) break;
        }
        RetVal = (RetVal << 4) + i;  //Warning, typing "0xG" will succeed but yield weird results

        ++Hex;
    }

    return RetVal;
}

// Prints an unsigned int using recursion
void PrintUNum(unsigned int num, unsigned int base)
{
    if( num / base )
       PrintUNum( num / base, base );

    putchar( CharRep[num % base] );
}

int main()
{
    unsigned int Val = HexToInt( "06F" );
    PrintUNum( Val, 2 );

    return 0;
}

Code: Select all

int HexToInt(const char *data) {
  int cval = 0;
  while (*data != '\0') {
    cval <<= 4;
    int tval = *data;
    tval -= '0';
    if (tval > 9) tval -= ('A' - '9');
    if (tval > 15) tval -= ('a' - 'A');
    cval += tval;
  }
  return cval;
}