Built-in Objects Reference

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The UTXO_Compiler contract language provides two built-in objects: BVM and self. This document covers the names, purposes, properties, methods, and usage examples for each object, aiming to provide developers with a clear and accurate usage guide.

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1. Self Object

• Object Name: Self
• Description: A built-in object representing the concept of "self", used for member access related to the current context.
• Example:

  # Using the Self object property
  def verify_key(signature: string):
      result = CheckSig(self.pubKeyHash, signature)

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2. BVM Object

• Object Name: BVM (Bytecode Virtual Machine)
• Description: A built-in object representing the bytecode virtual machine, providing access to VM metadata such as version, input/output counts.
• Predefined Member Mapping Table:

  Member Name	Corresponding Value	Purpose
  "version"	1	VM version number
  "locktime"	2	Lock time
  "inputCount"	3	Number of inputs
  "outputCount"	4	Number of outputs
  "inputsHash"	5	Hash of input data
  "unlockingInput"	6	Unlocking input data
  "outputsHash"	7	Hash of output data

• Example:

  # Process transaction data and verify
  tx_data = Cat(pretx.VLIO, tx_data)  # concatenate transaction data
  txid = Hash256(tx_data)  # compute transaction ID
  
  # Access BVM object metadata
  meta_data = BVM.unlockingInput  # get unlocking input metadata
  {meta_data_txid, meta_data_remain} = Split(meta_data, 32)  # extract transaction ID from metadata
  
  EqualVerify(txid, meta_data_txid)  # verify transaction ID consistency

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Next Steps

• Language Specification — Complete formal grammar definition

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