How do you make an object in C? Used in RTOS.

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I went through the EE445M and found it’s interesting since the goal of this class is to build a working RTOS. The first lec note mentioned how to make an object in C. The example he used is the “FIFO”.

http://stackoverflow.com/questions/2750270/c-c-struct-vs-class

There are 2 things to learn:

1. “##”: this is called token paste operator, “\”is like “…”in MATLAB, just means next line is connected to current line.

2. C doesn’t support OOP (encapsulation, inheritance, polymorphism). In here, we are trying to mimic encapsulation in C.

// macro to create a pointer FIFO// Comment: NAME is the param to rename the var, functions inside the "class"#define AddPointerFifo(NAME,SIZE,TYPE,SUCCESS,FAIL) \TYPE volatile *NAME ## PutPt;    TYPE volatile *NAME ## GetPt;    TYPE static NAME ## Fifo [SIZE];        void NAME ## Fifo_Init(void){ long sr;    sr = StartCritical();                   NAME ## PutPt = NAME ## GetPt = &NAME ## Fifo[0];   EndCritical(sr);                      }                                       int NAME ## Fifo_Put (TYPE data){         TYPE volatile *nextPutPt;               nextPutPt = NAME ## PutPt + 1;          if(nextPutPt == &NAME ## Fifo[SIZE]){     nextPutPt = &NAME ## Fifo[0];         }                                       if(nextPutPt == NAME ## GetPt ){          return(FAIL);                         }                                       else{                                     *( NAME ## PutPt ) = data;              NAME ## PutPt = nextPutPt;              return(SUCCESS);                      }                                     }                                       int NAME ## Fifo_Get (TYPE *datapt){      if( NAME ## PutPt == NAME ## GetPt ){     return(FAIL);                         }                                       *datapt = *( NAME ## GetPt ## ++);      if( NAME ## GetPt == &NAME ## Fifo[SIZE]){     NAME ## GetPt = &NAME ## Fifo[0];     }                                       return(SUCCESS);                      }                                       unsigned short NAME ## Fifo_Size (void){  if( NAME ## PutPt < NAME ## GetPt ){      return ((unsigned short)( NAME ## PutPt - NAME ## GetPt + (SIZE*sizeof(TYPE)))/sizeof(TYPE));   }                                       return ((unsigned short)( NAME ## PutPt - NAME ## GetPt )/sizeof(TYPE)); }// e.g.,// AddPointerFifo(Rx,32,unsigned char, 1,0)// SIZE can be any size// creates RxFifo_Init() RxFifo_Get() and RxFifo_Put()

Ref:

1. lec note of EE 445M

2. http://www.cprogramming.com/reference/preprocessor/token-pasting-operator.html

3. http://complete-concrete-concise.com/programming/c/preprocessor-the-token-pasting-operator

4. http://c.learncodethehardway.org/book/ex19.html