Write the function htoi(s) , which converts a string of hexadecimal digits (including an optional 0x or 0X) into its equivalent integer value. The allowable digits are 0 through 9, a through f, and A through F .

Is this a good solution? Are all cases covered in this code? I did take care of variable overflow aswell.

Is this how they intended for this function to look like?

Code:

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <ctype.h>
unsigned int htoi(char s[])
{
unsigned int val = 0;
int x = 0;
if(s[x] == '0' && (s[x+1]=='x' || s[x+1]=='X')) x+=2;
while(s[x]!='\0')
{
if(val > UINT_MAX) return 0;
else if(s[x] >= '0' && s[x] <='9')
{
val = val * 16 + s[x] - '0';
}
else if(s[x]>='A' && s[x] <='F')
{
val = val * 16 + s[x] - 'A' + 10;
}
else if(s[x]>='a' && s[x] <='f')
{
val = val * 16 + s[x] - 'a' + 10;
}
else return 0;
x++;
}
return val;
}
int main(int argc, char *argv[])
{
char hexalpha[] = "0xFFF";
char test[] = "adfa";
if(htoi(hexalpha)==0) printf("\nHex string overflow or not a hex character.\n");
else printf("%u\n", htoi(hexalpha));
getchar();
return 0;
}