convert a string to hex integer in C

Question

I have the following C string

"72e4247d3c91f424c62d909d7c1553a5"

It consists of 32 hex digits. It is an array with 4 integers in hex. How can I get back the numbers in form of integers from this array?

Answer 1

You'll have to parse the four 32-bit/8 hex digit chunks separately. The easiest way to do that is

#include <stdint.h>
#include <stdlib.h>
#include <string.h>

void parse_hex4(char const *str, uint32_t num[4])
{
    char buf[9];  // 8 hex digits + NUL

    buf[8] = '\0';
    for (int i=0; i<4; i++) {
        memcpy(buf, str + i * 8, 8);
        num[i] = strtoul(buf, NULL, 16);
    }
}

This assumes str is zero-padded to be exactly 32 characters long and it does no input validation. If you're using the compiler from Redmond that is stuck in the 1980 , use unsigned long instead of uint32_t .

Answer 2

Have you tried strtol ?

int val = (int) strtol (hex_string, NULL, 16);

Repeat on substrings if it is a flattened array.

Regards