ByteArray bytes = cf.getBytes();
ConstantPool pool = cf.getConstantPool();
int idx = bytes.getUnsignedShort(offset);
CstUtf8 cst = (CstUtf8) pool.get(idx);
Attribute result = new AttSourceFile(cst);
if (observer != null) {
observer.parsed(bytes, offset, 2, "source: " + cst);
}