Function pointers

Here is an example, we have a structure named Slice, the function like ‘get_direct_motion_vectors’ should really be put inside this structure. So we can use ‘Slice->get_direct_motion_vectors(…)’instead of just call that function. So put a function pointer inside the structure is a good one:

typedef struct slice
{
    int picture_id;
    void (*get_direct_motion_vectors)    (Macroblock *currMB);
    ...
}Slice;
 
// Usage: 
(*currSlice)->get_direct_motion_vector = Get_MV;
 
// where ‘Get_MV’ is defined in another .h file: mv_search.h
extern void Get_MV(Macroblock *currMB);
 
// and it is implemented in .c file: mv_search.c
void Get_MV(Macroblock *currMB) { . . .}