Possible `StringScanner#scan_float` method

strscan-part.c

static VALUE
strscan_scan_float(VALUE self)
{
    struct strscanner *p;
    double retval;
    char *start;
    char *end;

    GET_SCANNER(self, p);
    if (EOS_P(p))
        return Qnil;

    start = S_PBEG(p) + p->curr;
    while (ISSPACE(*start)) start++;
    if (start[0] == '0' && (start[1] == 'x' || start[1] == 'X'))
        return Qnil;

    retval = strtod(start, &end);
    if (errno == ERANGE) {
        errno = 0;
        rb_invalid_str(S_PBEG(p), "scan_float");
    }
    if (start == end)
        return Qnil;

    CLEAR_MATCH_STATUS(p);

    p->prev = p->curr;
    p->curr += end - S_PBEG(p) - p->prev;
    MATCHED(p);
    adjust_registers_to_matched(p);

    return DBL2NUM(retval);
}