DISTRIBUTED COMPUTING - Passing parameters in stubs

Passing parameters in stubs

To evaluate a parameter that you intend to pass in a remote procedure call, you need to identify what type of parameter it is (in, out, or in-out) and whether you use the parameter monomorphically or polymorphically. You can use parameters in other ways, but staying to these canonical types provides a clean interface.

Common C++ calling types based on the parameter type and usage:

Use In Out In-out

Common C++ calling types based on para-meter type and use Mono-morphic const T p const T& p return T; T& p T& p

Poly-morphic const T& p return T*; T*& p T*& p

Monomorphic in parameters include const T p and const T& p. Whether you choose a const T or a const T& usually depends on the size of the class. Returning a T or using a T& p parameter depends on the size of the class and the number of out parameters.

Table 2 and Table 3 show the typical syntax of caller stub and dispatcher stubs based on these parameter types.

Usage In Out In-Out

Caller stub syntax Mono-morphic p >>= stream; SendRequest(); SendRequest(); p <<= stream; p >>= stream; SendRequest(); p << stream;

Poly-morphic stream.FlattenPointer(&p); SendRequest; SendRequest(); p = (T*)(stream.Resurrect()); stream.FlattenPointer(&p); SendRequest(); delete p; p = (T*)(stream.Resurrect());

Usage In Out In-Out

Dispatcher stub syntax Mono-morphic T p; p <<= stream; implementation T p; implementation p >>= transport; T p; p <<= stream; implementation p >>= transport;

Poly-morphic T* p; p = (T*)(stream.Resurrect()); implementation delete p; T* p; implementation stream.FlattenPointer(&p); delete p; T* p; p = (T*)(stream.Resurrect()); implementation stream.FlattenPointer(&p); delete p;

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	Use	In	Out	In-out
Common C++ calling types based on para-meter type and use	Mono-morphic	const T p const T& p	return T; T& p	T& p
Common C++ calling types based on para-meter type and use	Poly-morphic	const T& p	return T; T& p	T*& p

	Usage	In	Out	In-Out
Caller stub syntax	Mono-morphic	p >>= stream; SendRequest();	SendRequest(); p <<= stream;	p >>= stream; SendRequest(); p << stream;
Caller stub syntax	Poly-morphic	stream.FlattenPointer(&p); SendRequest;	SendRequest(); p = (T*)(stream.Resurrect());	stream.FlattenPointer(&p); SendRequest(); delete p; p = (T*)(stream.Resurrect());