Data encapsulation in C

Question

I am currently working on an embedded system and I have a component on a board which appears two times. I would like to have one .c and one .h file for the component.

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Answer 1

You can:

1. Make your whole ads1248_options_t an opaque type (as already discussed in other answers)

2. Make just the adc_values member an opaque type, like:

    // in the header(.h)
   typedef struct adc_values adc_values_t;
   
    // in the code (.c)
   struct adc_values { 
       int32_t *values;
   };
   

3. Have a static array of array of values "parallel" to your ads1248_options_t and provide functions to access them. Like:

   // in the header (.h)
   int32_t get_adc_value(int id, int value_idx);
   
   // in the code (.c)
   static int32_t values[MAX_ADS][MAX_VALUES];
   // or
   static int32_t *values[MAX_ADS]; // malloc()-ate members somewhere
   
   int32_t get_adc_value(int id, int value_idx) {
       return values[id][value_idx]
   }
   

   If the user doesn't know the index to use, keep an index (id) in your ads1248_options_t.

4. Instead of a static array, you may provide some other way of allocating the value arrays "in parallel", but, again, need a way to identify which array belongs to which ADC, where its id is the simplest solution.