Studio:AutoScript Functions

 

Overview

This section describes basic functionality for ascript function processing. For ease of understanding, this section describes overall concepts and then describes the precise functionality that STRIDE provides.

Function Interception

Must of the functionality that STRIDE offers centers around the ability to intercept function calls between a host and a target.

Ownership vs. Usage

STRIDE has the concept of a Function Owner and a Function User. In general STRIDE usage the Owner and User imply target and host, but for messaging this meaning is transparent. A Message Owner may be on the host or the target. A Message User may be on the host or target.

Function User

A Function User may be any script that is not registered as the function owner or function override owner. The Function User may be access via the message as ascript.Functions.Item.User.

Function Owner

The Function Owner is the script that has successfully registered itself as the owner of the function (by calling the Register method). A function will only have one registered owner. Calls to register a second owner will result in an exception will be thrown. Ownership can be surrendered by calling the Unregister method (or by exiting the script that registered ownership). The Function Owner may be accessed via ascript.Functions.Item.Owner.

Override Owner

The Message Override Owner of a message is the script that successfully registered as the override owner (using the RegisterOverride method). An override owner is used to bypass the registered owner. If a message has an override owner registered, message transfers are sent to the registered override owner and not the registered owner. This allows the ability to code scripting with the registered owner, but to bypass the registered owner for certain processing for a variety of reasons (i.e. some code not implemented for the registered owner, some exception cases, etc.). It is legal for a script to declare both forms of message ownership. Thus, the same script may be both registered owner and the registered override owner.

Function Payloads

Payloads are Dynamic Objects containing data related to a message. A One-Way Command message may have a Command Payload. A One-Way Response message may have a Response Payload. A Two-Way Message may have both a Command Payload and a Response Payload. The word 'may' is used here because these are the legal conditions of what payloads may exist. For a Command Payload to exist, the captured message must take one or more parameters. For a Response Payload to exist, the captured message must be defined with a response payload.

These payloads are defined as properties for both a Message User and a Message Owner. By being part of both user and owner allows their values can be checked for validity in the event that a message didn't make it from user to owner (or visa-versa).

Synchronous / Asynchronous Interception

Messages that are sent between a Message Owner and a Message User will be either asynchronous or synchronous.

Asynchronous

An asynchronous message is also known as a "non-blocking" message. This is the type of messaging that occurs for Broadcast messaging, One-Way Command messaging, and One-Way Response messaging. For asynchronous messaging:
1. The initiator script of the action makes a call to transfer a payload (either a command or response).
2. The payload is logged onto the receiving script's event queue.
3. The initiator script continues processing.
4. Later the receiving script makes a call to WaitForEvent to processing the payload.

The initiator script was not blocked from continuing processing.

Synchronous

A synchronous message is also known as a "blocking" message. Only a Two-Way message is synchronous for STRIDE. For synchronous messaging:
1. The initiator script makes a call to transfer a command payload.
2. The initiator script then waits until the receiving script provides a response (perhaps with a response payload).

The initiator script was blocked from continuing processing until the receiving script responded.