How to generate a v5 UUID with uuid_generate_sha1

Question

I want to generate a v5 UUID for a string using a given namespace.

https://man.archlinux.org/man/uuid_generate_time.3.en talks about uuid_generate_sha1() but I could not find any good examples on how to use them in our code.

My pseudocode looks like:

_generate_v5_uuid(const char *inputStr, const char *namespace, char **outputString)
{
        uuid_t uuid;
        uuid_generate_sha1(inputStr, &uuid);

        *outputStr = convert_uuid_to_string(uuid);
        return;
}

What exactly needs to be passed to uuid_generate_sha1?

Answer 1

I have written this example for you:

#include <uuid/uuid.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char *convert_uuid_to_string(uuid_t uuid) {
    char *buf = NULL;
    size_t s = 0;
    FILE *f = open_memstream(&buf, &s);
    for (size_t i = 0; i < 16; ++i) {
        fprintf(f, "%02x", uuid[i]);
    }
    fclose(f);
    return buf;
}


char *generate_v5_uuid(const char *inputStr, const char *namespace) {
    const uuid_t *ns = uuid_get_template(&namespace[1]);
    uuid_t uuid;
    uuid_generate_sha1(uuid, *ns, inputStr, strlen(inputStr));
    return convert_uuid_to_string(uuid);
}


int main() {
    system("set -x ; uuidgen --sha1 -n @url -N string");
    printf("%s\n", generate_v5_uuid("string", "@url"));
}

The program outputs:

$ ./a.out 
+ uuidgen --sha1 -n @url -N string
64be9091-88e8-5476-996b-8b541f7bf3e5
64be909188e85476996b8b541f7bf3e5