decode

static VALUE
ossl_asn1_decode(VALUE self, VALUE obj)
{
    VALUE ret, ary;
    unsigned char *p;
    long offset = 0;
    volatile VALUE tmp;

    obj = ossl_to_der_if_possible(obj);
    tmp = rb_str_new4(StringValue(obj));
    p = (unsigned char *)RSTRING_PTR(tmp);
    ary = ossl_asn1_decode0(&p, RSTRING_LEN(tmp), &offset, 0, 1, 0);
    ret = rb_ary_entry(ary, 0);

    return ret;
}