Attribute Macro pbc_contract_codegen::zk_on_variables_opened

#[zk_on_variables_opened]

Secret variable opened zero-knowledge contract annotation

OPTIONAL HOOK: This is an optional hook, and is not required for a well-formed zero-knowledge contract. The default behaviour is to do nothing.

If the annotated function panics changes to the contract state will be rolled back.

Annotated function is automatically called when a contract opens one or more secret variables; this can only happen after the use of ZkStateChange::OpenVariables. This hook is exclusively called by the blockchain itself, and cannot be called manually from the dashboard, nor from another contract.

Allows the contract to automatically react to opening of ZK variables.

Annotated function must have a signature of following format:

#[zk_on_variables_opened]
pub fn zk_on_variables_opened(
  context: ContractContext,
  state: ContractState,
  zk_state: ZkState<Metadata>,
  opened_variables: Vec<SecretVarId>,
) -> (ContractState, Vec<EventGroup>, Vec<ZkStateChange>)

Where opened_variables is a Vec of the opened variables.

Example

Common usages include post-processing of computation results; for example

#[zk_on_variables_opened]
pub fn zk_on_sum_variable_opened(
  context: ContractContext,
  mut state: ContractState,
  zk_state: ZkState<Metadata>,
  opened_variables: Vec<SecretVarId>,
) -> (ContractState, Vec<EventGroup>, Vec<ZkStateChange>) {
    let result_var_id: SecretVarId = *opened_variables.get(0).unwrap();
    let result_var: ZkClosed<Metadata> = zk_state.get_variable(result_var_id).unwrap();
    let result: Vec<u8> = result_var.data.as_ref().unwrap().clone();
    state.push(result);
    (state, vec![], vec![])
}