Merged GModule branch! in Valum

Valum now support dynamically loadable server implementation with GModule!

Server are typically looked up in /usr/lib64/vsgi/servers with the libvsgi-<name>.so pattern (although this is highly system-dependent).

This works by setting the RPATH to $ORIGIN/vsgi/servers of the VSGI shared library so that it looks into that folder first.

The VSGI_SERVER_PATH environment variable can be set as well to explicitly provide a directory containing implementations.

To implement a compliant VSGI server, all you need is a server_init symbol which complies with ServerInitFunc delegate like the following:

[ModuleInit]
public Type server_init (TypeModule type_module) {
    return typeof (VSGI.Custom.Server);
}

public class VSGI.Custom.Server : VSGI.Server {
    // ...
}

It has to return a type that is derived from VSGI.Server and instantiable with GLib.Object.new. The Vala compiler will automatically generate the code to register class and interfaces into the type_module parameter.

Some code from CGI has been moved into VSGI to provide uniform handling of its environment variables. If the protocol you want complies with that, just subclass (or directly use) VSGI.CGI.Request and it will perform all the required initialization.

public class VSGI.Custom.Request : VSGI.CGI.Request {
    public Request (IOStream connection, string[] environment) {
        base (connection, environment);
    }
}

For more flexibility, servers can be loaded with ServerModule directly, allowing one to specify an explicit lookup directory and control when the module should be loaded or unloaded.

var cgi_module = new ServerModule (null, "cgi");

if (!cgi_module.load ()) {
    assert_not_reached ();
}

var server = Object.new (cgi_module.server_type);

I received very useful support from Nirbheek Chauhan and Tim-Philipp Müller for setting the necessary build configuration for that feature.