The program I wrote works in demographics consisting of only single Hexadecimal values. (Probably not the most elegant solution, but I'm a new programmer) My question is, how would I go about handling of multiple hexadecimal digits, such as 0xAF, or 0xFF, etc? I'm not exactly sure, and I've seemed confuse myself greatly, in the attempt. I'm not asking for someone to hold my hand, but to give me a tip where I've gone wrong in this code and thoughts on how to fix it.
Thanks :)
/* Exercise 2-3. Write the function htoi(s), which converts a string of
* hexadecimal digits (including an optional 0x or 0X) into it's equivalent
* integer value. The allowable digits are 0...9 - A...F and a...f.
*
*/
#include <stdio.h>
#include <string.h>
#define NL '\n'
#define MAX 24
int htoi(char *hexd);
int
main(void)
{
char str[MAX] = {0};
char hex[] = "0123456789ABCDEFabcdef\0";
int c;
int i;
int x = 0;
while((c = getchar()) != EOF) {
for(i = 0; hex[i] != '\0'; i++) {
if(c == hex[i])
str[x++] = c;
}
if(c == NL) {
printf("%d\n", htoi(str));
x = 0, i = x;
}
}
return 0;
}
int
htoi(char *hexd)
{
int i;
int n = 0;
for(i = 0; isdigit(hexd[i]); i++)
n = (16 * i) + (hexd[i] - '0');
for(i = 0; isupper(hexd[i]); i++) /* Let's just deal with lowercase characters */
hexd[i] = hexd[i] + 'a' - 'A';
for(i = 0; islower(hexd[i]); i++) {
hexd[i] = hexd[i] - 'a';
n = (16 + i) + hexd[i] + 10;
n = hexd[i] + 10;
}
return n;
}
I think that the MAX size of string should be either 10 or 18 instead of 24. (If you have already checked the
int
on your machine and followed the reasoning bellow, it would be beneficial to include it as a comment in your code.)10 : since
htoi()
returns anint
, int is usually 4 bytes (check your system's too), so the hexadecimal number can be atmost 8 digits in length (4bits to 1 hex digit, 8 bits to a byte), and we want to allow for the optional0x
or0X
.18 : would be better if
htoi()
returned along
and its 8 bytes (again, check your system's), so the hexadecimal number can be atmost 16 digits in length, and we want to allow for the optional0x
or0X
.Please note that that sizes of
int
andlong
are machine dependent, and please look at exercise 2.1 in the K&R book to find them.