Simulink Buses with Pointer and Reflection inspect

Sometimes the same algorithms should be uses in traditional C / C++-programming and for models designed with Matlab-Simulink. For the model simulation level that C-sources can be used in form of Simulink S-Functions. If the model was translated to C-code with the Simulink-Codegen feature, the core routines of the S-function are immediately invoked in the translated code of the model.

What about Object Oriented Programming, which is usual in C++, which can be used in C-algorithm too. The C-algorithm which are traditionally used in C may be Object-Oriented. Object Orientation in its core (substantial) meaning is the binding of routines (C-functions, methods, operations) to its data. The data can be structured in C in struct { ...}. If a method respectively C-function works with its specific data, it is Object-Oriented. Associations, Aggregations and Compositions between classes are built with pointer (references) to other struct. The abstraction respectively inheritance is a important feature of Object Orientation, but not the substantial one. Abstraction in C can be done with reference types to a head struct type inside the derived structures, see the example.

Is there any commonality between a Simulink model and Object Orientation? A Simulink model presents a data flow thinking. Data are provided from one block and processed from another block (or module) in the calculation order. Object Orientation does not show the data flow (may be in sequence diagrams). Object model diagrams show the dependency between classes or moduls, the knowledge of the other data. But both worlds are able to join together. The Simulink model shows the data flow and calculation order of routines. Some Simulink blocks which uses the same bus inputs and outputs can be conceived as methods of the data which are presented in the bus types. The buses are the data structs or classes, and the using blocks are the methods or operations in Object Orientation.

Why this topic? Conventional Programming is a common practice, Object Orientation is an important style of conventional Programming. Embedded Software is often programmed in C or a lightweight C++. Simulink modelling with Code generation is a good idea of programming of embedded systems which can or should replace the conventional programming step by step, but not totally, more conglomerating. Both thinking areas should be joined therefore.

It is possible to deal with pointer in Simulink Buses which can be used in C in generated code, or in S-functions, not in pure Simulink.

The last one, I think simulink has a paradigm: Data flow from input to output. Pointers offers the possibility to set data backward, from an output bus into the module. That is not desired, therefore pointers in buses are not firstly supported. But for solutions in the C-environment pointers may be a point of interest.

In the header file you should define a union:

typedef struct MyBus_t {
  /*unnamed union*/
  union { int32 myRefBus_int[2]; MyRefBus* myRefBus; };
  //... some more elements;
} MyBus;

The Simulink Bus definition should contain only the myRefBus_int element as int32 array of 2 dimensions. The next topic is a S-function which converts any desired Bus to the int32[]. S-functions have pointers as input if the input is a bus at model level. Arrays are also presented as pointners. Therefore the S-function "Bus2ptr" has the following definition in the mex.c file: