TX vchdata serialization definition

To use TX, the following conditions must be met at the same time

1. nType = TX_TOKEN
2. sendTo: the address type is pubkey,or TemplateId = TEMPLATE_WEIGHTED / TEMPLATE_MULTISIG
3. vchData is not null

0               16   20 21        x                                              E
|________________|____|_|_________|______________________________________________|

• byte0 ~ byte15 : UUID （RFC 4122)
• byte16 ~ byte19 : timestamp (UTC in second)
• byte20 : szDesc , strDescription size，if the value is 0, it is said that no strdescription field
• If "szDesc" value is not 0, Strdescription from 21st byte，size is "szDesc". Strdescription needs to be encoded with Base64, and the encoded length cannot exceed 255 bytes.
• Then there are user-defined data segments. It is recommended to use “MessagePack/BSON” for encapsulation

NOTE: The application is indexed by UUID, and TX query and retrieval can be performed by UUID and timestamp.