text: public virtual ObjectId IdFor(int type, byte[] data, int off, int len){MessageDigest md = Digest();md.Update(Constants.EncodedTypeString(type));md.Update(unchecked((byte)' '));md.Update(Constants.EncodeASCII(len));md.Update(unchecked((byte)0));md.Update(data, off, len);return ObjectId.FromRaw(md.Digest());}