message: Add comments for register SP parser API call.
diff: @@ -1618,9 +1618,36 @@ pub extern fn indy_parse_get_revoc_reg_delta_response(command_handle: i32,
  res
  }
  +/// Callback type for parsing Reply from Node to specific StateProof format
  +///
  +/// # params
  +/// reply_from_node: string representation of node's reply ("as is")
  +/// parsed_sp: out param to return serialized as string JSON with array of ParsedSP
  +///
  +/// # return
  +/// result ErrorCode
  +///
  +/// Note: this method allocate memory for result string `CustomFree` should be called to deallocate it
  pub type CustomTransactionParser = extern fn(reply_from_node: *const c_char, parsed_sp: *mut *const c_char) -> ErrorCode;
  +
  +/// Callback type to deallocate result buffer `parsed_sp` from `CustomTransactionParser`
  pub type CustomFree = extern fn(data: *const c_char) -> ErrorCode;
  +
  +/// Register callbacks (see type description for `CustomTransactionParser` and `CustomFree`
  +///
  +/// # params
  +/// command_handle: command handle to map callback to caller context.
  +/// txn_type: type of transaction to apply `parse` callback.
  +/// parse: required callback to parse reply for state proof.
  +/// free: required callback to deallocate memory.
  +/// cb: Callback that takes command result as parameter.
  +///
  +/// # returns
  +/// Status of callbacks registration.
  +///
  +/// # errors
  +/// Common*
  #[no_mangle]
  pub extern fn indy_register_transaction_parser_for_sp(command_handle: i32,
  txn_type: *const c_char,
  