Contract-key API

[sanity]

A WebAssembly contract-key will implement the following functions:

trait ContractKey {
  /// Determine whether this value is valid for this contract
  fn validate_value(value : &Vec<u8>) -> bool;

  /// Determine whether this value is a valid update for this contract. If it is, modify
  /// the value and return true, else return false.
  fn update_value(value: &mut Vec<u8>, value_update: &Vec<u8>) -> bool;

  /// Obtain any other related contracts for this value update. Typicall used to ensure 
  /// update has been fully propagated.
  fn related_contracts(value_update : &Vec<u8>) -> Vec<ContractKey>;

  /// Extract some data from the value and return it.
  ///
  /// eg. `extractor` might contain a byte range, which will be extracted
  /// from the value and returned.
  fn extract(extractor : &Vec<u8>, value : &Vec<u8>) -> Vec<u8>;
}