Programmatically populate a uint8_t array

Question

I have a uint8_t array which should look like this .

uint8_t code[1000] = {0x66, 0xba, 0xf8, 0x03}

Now I cant hard code values in that array instead , I need to insert them one by one from char buffer[300]. The content of char buffer[300] is a space delimited string of hex values "66 ba f8 03"

The code I wrote is -

        char* token = strtok(buffer, " "); 
        // Keep printing tokens while one of the 
        // delimiters present in str[].
        int pc = 0; 
        while (token != NULL) {
            code[pc] = token; // This part is wrong. I need to cast it properly
            token = strtok(NULL, " "); 
            pc++;
        }

How can I convert a string value into a uint8_t value?

Answer 1

Example code that uses strtol to convert hex number strings.

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

int main(void)
{
    char buffer[300] = "66 ba f8 03";

    uint8_t code[1000];

    long val;
    char *endptr;

    char* token = strtok(buffer, " "); 
    // Keep printing tokens while one of the 
    // delimiters present in str[].
    int pc = 0; 
    while (token != NULL) {

        /* convert as a base16 number */
        val = strtol(token, &endptr, 16);

        /* The character following the number should be the end of the string as the input string is already tokenized. */
        if(*endptr) {
            /* error handling */
        } else if(val < 0) {
            /* error handling */
        } else if(val > UINT8_MAX) {
            /* error handling */
        } else {
            /* The checks above make sure that the value fits into uint8_t. */
            code[pc] = (uint8_t)val;
        }

        token = strtok(NULL, " "); 
        pc++;
    }

    for(int i = 0; i < pc; i++) {
        printf("code[%d] = 0x%02x\n", i, code[i]);
    }

    return 0;
}

The error handling depends on the rest of your program.

Notes:

strtok modifies the input string, so it must not be a const char[] or a string literal.

The loop doesn't contain a check to out-of-range access to code[pc].

Edit in the code above: A check for space in *endptr is unnecessary as space is used as the token delimiter, so we should never find a space in the result of strtok.