From World Wind Wiki
A C#/VB/JScript.NET Plugin Engine was added to World Wind in version 1.3.2.
[edit] Features
- Dynamic compilation and execution of script code written in the following languages:
- Load plugins from precompiled .dll files
- Full access to World Wind internals (same as internal code)
- Runs at full speed (compilation on load)
[edit] Engine logic
When World Wind starts the following steps are performed:
- The PluginCompiler scans bin\Plugins directory and the 1st level subdirectories of the plugin directory for files ending in any of the supported file extensions.
- When it finds one it tries to compile the source (to memory) with references to the same assemblies as the app has referenced.
- It then searches the compiled assembly for an implementation of Plugin.
[edit] Benefits
- Since the compiler for C#,VB and JSCript comes with the .Net Framework no additional third party library is required.
- For other languages (like J#) an install will be needed, and unfortunately I haven’t found an easy way of enumerating all available compilers (before .Net 2.0)
- Very fast on-the-fly compilation of the scripts.
- Scripts executes with same speed as a precompiled assembly.
- Debuggable inside World Wind project (World Wind in debug build loads internal plugins)
- Custom dlls may be dynamically loaded
[edit] Drawbacks
- Security: The script could wipe out the hard drive or worse. But with a script at least the user can verify the intentions by looking at the source. Even current add-ons (layers) are often .exe installers giving the user no way of identifying evil code.
- To unload a script’s assembly from memory completely, WW needs a restarted (there are workarounds (appdomains))
- With no nailed down limited interface into WW the script could stop working on a new version of WW.
[edit] Problems
- Serializing generic lists (List<SomeClass>) won’t work; use a normal array or an ArrayList instead
[edit] Security Lockdown Fix
Following this example we should be able to lockdown FileIO to the AppDir
public static string ReadFile(string filename)
{
string appDir = Directory.GetCurrentDirectory();
FileIOPermission f = new FileIOPermission(PermissionState.None);
f.SetPathList(FileIOPermissionAccess.Read, appDir);
f.SetPathList(FileIOPermissionAccess.PathDiscovery, appDir);
f.PermitOnly();
// Use Path.GetFilePath() to canonicalize the file name
// Use FileStream.OpenRead to open the file
// Use FileStream.Read to access and return the data
}
From Code Access Security in Practice – MSDN
[edit] Code Translator
C#<->VB [1]
So no one can complain about languages. 🙂
[edit] External links
