ScriptEngine

By | 2007.08.04

The time has come to start implementing script support into OpenSim.

ScriptEngine (SE)
OpenSim will have an interface for SE. It will load SE dynamically using reflection. SE will be in separate .dll Assembly.
During load SE will hook itself up to the necessary events in OpenSim.
This includes: Object rez (look for active scripts), object derez and all events relating to objects (touch, sit, etc).

SE might also during startup need to iterate through existing objects to see what scripts it needs to start. This depends on at what point SE is loaded.

All access to OpenSim from scripts will go through SE.

Compiler
When SE starts a script it will determine script type. If script type is LSO (LSL ByteCode) the script will be compiled into .Net Assembly .dll before load. Compiler is a separate .dll Assembly, but hardcoded into SE.

Loading scripts
* If script is LSO, compile to .Net Assembly
* Modify .Net Assembly to support microthreading (will be done later in project)
* Find available AppDomain for the script (currently only default appdomain)
* Load script into AppDomain
* Create a private instance of BuiltIn commands for the script
* Create object of script handing it the private BuiltIn command instance

Some BuiltIn functions will require information about who is executing them, for example for object permissions or feedback events. Because .Net Assembly can not be trusted (it is uploaded by users) ScriptEngine will create a private instance of BuiltIn commands. This instance will contain and pass on the necessary ID’s to OpenSim – as well as work as a translator between LSL-functions and OpenSim API.

Operation
A script instance is made up of ScriptID and ObjectID. This should always result in an unique combination for any script.

ScriptEngine will receive events from OpenSim and forward the events to the required scripts. During this forward it will also enforce microthreading.

Current Status
Class OpenSim.ScriptEngine.DotNetEngine.ScriptEngine has basic framework and is able to load and execute scripts. Only missing event hookups and actual implementation into OpenSim.

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