#include <string.h>
#include <stdio.h>
#include <ctype.h>

struct substr {
    char *str;
    unsigned len;
};

struct substr substr_from_str(char *s) {
    return (struct substr){.str = s, .len = strlen(s)};
}

int substr_to_int(struct substr s, int *num) {
    int ret = 0;
    int sign = (s.str[0] == '-');
    int start = sign ? 1 : 0;
    for(int i = start; i < s.len; i ++) {
        char c = s.str[i];
        if(!isdigit(c)) {
            return 0;
        }
        ret *= 10;
        ret += c - '0';
    }
    *num = sign ? - ret : ret;
    return 1;
}

struct substr trim_spaces_back(struct substr s) {
    for(int i = s.len-1; i >= 0; i --) {
        if(s.str[i] != ' ') {
            s.len = i + 1;
            return s;
        }
    }
    return (struct substr){.str = s.str, .len = 0};
}
struct substr cut_number_back(struct substr *s) {
    for(int i = s->len-1; i >= 0; i --) {
        if(!isdigit(s->str[i]) && s->str[i] != '-') {
            struct substr ret = {
                .str = s->str + i + 1,
                .len = s->len - i - 1
            };
            s->len = i + 1;
            return ret;
        }
    }
    return (struct substr){NULL, 0};
}
struct substr parse_int_back(struct substr *s) {
    *s = trim_spaces_back(*s);
    return cut_number_back(s);
}

int parse_line(char *str, int *uid, int *gid) {
    struct substr line = substr_from_str(str);
    struct substr gid_str = parse_int_back(&line);
    if(gid_str.str == NULL || gid_str.len == 0) {
        goto SPOOL_READ_ERROR;
    }
    struct substr uid_str = parse_int_back(&line);
    if(uid_str.str == NULL || uid_str.len == 0) {
        goto SPOOL_READ_ERROR;
    }
    return substr_to_int(uid_str, uid) && substr_to_int(gid_str, gid);
SPOOL_READ_ERROR:
    return 0;
}

int main() {
    int uid, gid;
    if(parse_line("asdf 1234 5678", &uid, &gid)) {
        printf("%d, %d\n", uid, gid);
    } else {
        printf("error\n");
    }
    return 0;
}