Scripted Comms Modules

A ScriptModule wraps up a class implemented in Carapace script.

• The ScriptModule allows a class implemented in Carapace script to be pushed onto a comms stack -- the scripted class must obey certain rules.
• The ScriptModule supplies default implementations for the standard methods so that the scripted class need not provide them all.

The following high-level protocols are implemented in Carapace script:

Click here for an example of a scripted comms module which can be wrapped up in a ScriptModule.

ScriptModule Creation

Given a scripted class which obeys the rules, a ScriptModule is made using the create function function. For example, the following creates a ScriptModule to wrap an Http module:

    (create ScriptModule "Http")

    (stack.push (create ScriptModule "Http"))

    (stack.top)

ScriptModule Properties

A ScriptModule supports only the standard comms module properties ie.

The existence of a property called isBottom on the scripted module allows the module to be placed at the bottom of a communications stack.

ScriptModule Methods

A ScriptModule supports only the standard comms module methods ie.

Scripted Communication Rules

For a scripted class to be valid as the basis for a comms module, the following rules must apply:

1. the primary interface (ie. interface number 0) must support the following properties:

   name	type
   log	Log
   stack	CommsStack

2. the primary interface (ie. interface number 0) must support one or more of the following methods:

   name	argument types	return type
   connect	none	empty List ()
   send	Buffer	Object
   receive	Integer	Object
   receiveInto	Buffer, Integer	empty List ()
   connect	none	empty List ()
   bind	none	empty List ()
   listen	Integer	empty List ()
   accept	Integer	CommsModule

Notes:

1. The reason for allowing the send method to return a value is that submission of a message to a message transfer service may result in a message id being passed back.
2. A scripted modules is most often used as the top layer on the stack. If such a module is to be used lower down the stack, then the receiveInto method should be supplied in preference to the receive method.