Strict encoding schema

Strict encoding schema is a library for handling binary strict encoding rules and a compiler from a human-readable data structure representation, written on a [Parsel] language, used by AluVM (or its subset Contractum used in RGB smart contracts) into a binary format.

Example of strict encoding schema declaration in Parsel/Contractum:

datapkg BP

alias Hash256 :: U8^32
alias Sha256 :: Hash256
alias Sha256d :: Hash256
alias Sha256t :: Hash256
alias Ripemd160 :: U8^20

alias BlockId :: Sha256d
alias Txid :: Sha256d

alias Amount :: U64

data OutPoint :: Txid, vout U16

data ScriptPubkey :: U8^..10_000
data StackByteStr :: U8^..520
data Witness :: StackByteStr^..1_000
data SigScript :: StackByteStr^..1_000

data TxOut :: Amount, 
              ScriptPubkey
data TxIn :: OutPoint, 
             nSeq U16, 
             SigScript, 
             Witness?

data Transaction :: ver U8, 
                    inputs TxIn*,
                    outputs TxOut*,
                    lockTime U32

Strict encoding schema library and compiler also covers StenPath - a standard for addressing specific fields and entries of strict-encoded data inside container (you may compare StenPath to XPath for XML) and its binary encoding which is used in STEN AluVM ISA extensions.

For instance, StenPath expression $1[5].$3[1][0] applied to Transaction data structure defined above it will return first byte of second item in witness stack of the second transaction input. In binary form StenPath can be read like FF 01 00 FE 05 00 FF 03 00 FE 01 00 FE 00 00.

Example of how this encoding can be used together with STEN ISA in AluVM assembly:

.ISA  ALU, BP, STEN

.MAIN
                    ;; Load transaciton with ID to s16[1]
                    bpltx   0xbdb657fe4633d4612e4096eb2cb9f575233cb007ae3a17245d80dad76afb33b9, s16[1]
                    ;; Define lookup path
                    put     0xFF0100_FE0500_FF0300_FE0100_FF0000, s16[3]

                    ;; Parses data from s16[1] according to ses-encoding found in s16[2]
                    ;; at data path encoded at s16[3] to register u8[1]
                    parse   s16[1], s16[2], s16[3], u8[1]