[Clam-devel] [PATCH] IMPORTANT change: making Processing::GetConfigure not mandatory

[Pau Arumi]

      Problem:

Processing interface include the pure abstract method.
virtual ProcessingConfig& GetConfig() const = 0;

In many cases processings does not need a configuration object,
however they are forced to implement GetConfig. Over the years
we've used different solutions for this case:
1- create a custom empty config class, and have a processing
attribute of this config class, which is returned in GetConfig()
2- implement GetConfig() with a throw 0; an assert or similar, so
the compiler does not complain about the non-existing return
statement.
3- (the way documented) in  the wiki: declare a static variable
of NullProcessingConfig inside GetConfig() and return it:
ProcessingConfig GetConfig() const
{
	static NullProcessingConfig config;
	return config;
}


The second problem is related to the constructor. Processings
writers have to write a default constructor that calls Configure( 
...)
passing the default config. Otherwise, the default
constructed processing will assert on Do time.

The solution at the wiki is:
	typedef CLAM::NullProcessingConfig Config;
	MyProcessing(const Config & config=Config())
	{
		Configure( config );
	}


None of these solutions is very obvious and make writing simple
processings quite difficult


     Solution


Implement virtual ProcessingConfig& GetConfigure() const at the
base class, returning a static NullProcessingConfig.

Change behaviour of Processing::Processing() so it leaves the
processing in Configured state.
So without the constructor and GetConfig methods a simple
processing looks like this:

class MyProcessing : public CLAM::Processing
{
	CLAM::InPort<float> mIn;
	CLAM::OutPort<float> mOut;
public:
	const char* GetClassName() const { return "MyProcessing"; 	}
  	~MyProcessing() {}

	// Configuration to the minimal expression
	bool ConcreteConfigure(const CLAM::ProcessingConfig&) { return 
true; }
	bool Do()
	{
		Do(mIn.GetData(), mOut.GetData());
		// Tell the ports this is done
		mIn.Consume();
		mOut.Produce();
		return true;
	}

	bool Do(const float& in, float& out)
	{
		// Your implementation
	}
}


If nobody discusses the solution in 24 hours I'll commit the
attached patch ;)

Pau


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