C में थोड़ी आभासीता जोड़ना

 #pragma once typedef struct base_iface* base_iface_ptr; typedef const char* (*get_name_func_ptr)( base_iface_ptr ); struct base_iface { get_name_func_ptr get_name; }; typedef struct base_iface base_iface; 

 #pragma once typedef struct sizible_iface* sizible_iface_ptr; typedef unsigned int (*get_size_func_ptr)( sizible_iface_ptr ); struct sizible_iface { get_size_func_ptr get_size; }; typedef struct sizible_iface sizible_iface; 

 #pragma once typedef struct point_t* point_ptr; typedef void (*point_print_coordinates_func)( point_ptr ); struct point_t //  base_iface  sizible_iface { // " " get_name_func_ptr get_name; get_size_func_ptr get_size; //  "" point_print_coordinates_func print_coordinates; //  int x; int y; }; typedef struct point_t point_t; //  point_t point_init( int x, int y ); //     point_ptr  base_iface_ptr base_iface_ptr point_to_base_iface( point_ptr ptr ); //     point_ptr  sizible_iface_ptr sizible_iface_ptr point_to_sizible_iface( point_ptr ptr ); 

 #pragma once typedef struct d3_point_t* d3_point_ptr; typedef void (*d3_point_print_coordinates_func)( d3_point_ptr ); struct d3_point_t //  base_iface  sizible_iface { //  "" d3_point_print_coordinates_func print_coordinates; // " " get_name_func_ptr get_name; get_size_func_ptr get_size; //  int x; int y; int z; }; typedef struct d3_point_t d3_point_t; //  d3_point_t d3_point_init( int x, int y, int z ); //     d3_point_ptr  base_iface_ptr base_iface_ptr d3_point_to_base_iface( d3_point_ptr ptr ); //     d3_point_ptr  sizible_iface_ptr sizible_iface_ptr d3_point_to_sizible_iface( d3_point_ptr ptr ); 

 #include "std.h" static point_ptr base_iface_to_point( base_iface_ptr ptr ); //  " "  base_iface static const char* point_get_name( base_iface_ptr ptr ) { static const char* null_point_ptr = "Null point"; static const char* some_point_ptr = "Some point"; point_ptr casted_ptr = base_iface_to_point( ptr ); const char* result = null_point_ptr; if( casted_ptr->x || casted_ptr->y ) { result = some_point_ptr; } return result; } static point_ptr sizible_iface_to_point( sizible_iface_ptr ptr ); //  " "  sizible_iface static unsigned int point_get_size( sizible_iface_ptr ptr) { point_ptr casted_ptr = sizible_iface_to_point( ptr ); unsigned int size = (unsigned int)( sizeof( casted_ptr->x ) + sizeof( casted_ptr->y ) ); return size; } //   ""  point_t static void point_print_coordinates( point_ptr ptr ) { printf( "x = %u, y = %u\n", ptr->x, ptr->y ); } //  point_t //       (private)  point_t point_init( int x, int y ) { point_t point; point.get_name = point_get_name; point.get_size = point_get_size; point.print_coordinates = point_print_coordinates; point.x = x; point.y = y; return point; } //       enum { num_get_name_offset = 0, num_get_size_offset = sizeof( get_name_func_ptr ), }; //    static point_ptr base_iface_to_point( base_iface_ptr ptr ) { return (point_ptr)( (char*)ptr - num_get_name_offset ); } base_iface_ptr point_to_base_iface( point_ptr ptr ) { return (base_iface_ptr)( (char*)ptr + num_get_name_offset ); } static point_ptr sizible_iface_to_point( sizible_iface_ptr ptr ) { return (point_ptr)( (char*)ptr - num_get_size_offset ); } sizible_iface_ptr point_to_sizible_iface( point_ptr ptr ) { return (sizible_iface_ptr)( (char*)ptr + num_get_size_offset ); } 

 #include "std.h" static d3_point_ptr base_iface_to_d3_point( base_iface_ptr ptr ); //  " "  base_iface static const char* d3_point_get_name( base_iface_ptr ptr ) { static const char* null_point_ptr = "Null 3D point"; static const char* some_point_ptr = "Some 3D point"; d3_point_ptr casted_ptr = base_iface_to_d3_point( ptr ); const char* result = null_point_ptr; if( casted_ptr->x || casted_ptr->y || casted_ptr->z ) { result = some_point_ptr; } return result; } static d3_point_ptr sizible_iface_to_d3_point( sizible_iface_ptr ptr ); //  " "  sizible_iface static unsigned int d3_point_get_size( sizible_iface_ptr ptr) { d3_point_ptr casted_ptr = sizible_iface_to_d3_point( ptr ); unsigned int size = (unsigned int) ( sizeof( casted_ptr->x ) + sizeof( casted_ptr->y ) + sizeof( casted_ptr->z ) ); return size; } //   ""  d3_point_t static void d3_point_print_coordinates( d3_point_ptr ptr ) { printf( "x = %u, y = %u, z = %u\n", ptr->x, ptr->y, ptr->z ); } //  d3_point_t //       (private)  d3_point_t d3_point_init( int x, int y, int z ) { d3_point_t point; point.get_name = d3_point_get_name; point.get_size = d3_point_get_size; point.print_coordinates = d3_point_print_coordinates; point.x = x; point.y = y; point.z = z; return point; } //       enum { num_get_name_offset = sizeof( d3_point_print_coordinates_func ), num_get_size_offset = num_get_name_offset + sizeof( get_name_func_ptr ), }; //    static d3_point_ptr base_iface_to_d3_point( base_iface_ptr ptr ) { return (d3_point_ptr)( (char*)ptr - num_get_name_offset ); } base_iface_ptr d3_point_to_base_iface( d3_point_ptr ptr ) { return (base_iface_ptr)( (char*)ptr + num_get_name_offset ); } static d3_point_ptr sizible_iface_to_d3_point( sizible_iface_ptr ptr ) { return (d3_point_ptr)( (char*)ptr - num_get_size_offset ); } sizible_iface_ptr d3_point_to_sizible_iface( d3_point_ptr ptr ) { return (sizible_iface_ptr)( (char*)ptr + num_get_size_offset ); } 

 #pragma once // system #include "stdio.h" // program #include "base_iface.h" #include "sizible_iface.h" #include "point.h" #include "3d_point.h" 

 #include "std.h" 

 #include "std.h" // ,      base_iface void print_name( base_iface_ptr ptr ) { printf( "name = \"%s\"\n", ptr->get_name( ptr ) ); } // ,      sizible_iface void print_size( sizible_iface_ptr ptr ) { printf( "size = %u\n", ptr->get_size( ptr ) ); } int main( int argc, const char* argv[] ) { //    point_t null_point = point_init( 0, 0 ); point_t some_point = point_init( 1, 5 ); d3_point_t d3_null_point = d3_point_init( 0, 0, 0 ); d3_point_t d3_some_point = d3_point_init( 0, 1, 0 ); //      print_name( point_to_base_iface( &null_point ) ); //      print_size( point_to_sizible_iface( &null_point ) ); //    null_point.print_coordinates( &null_point ); puts( "\n" ); //       print_name( point_to_base_iface( &some_point ) ); print_size( point_to_sizible_iface( &some_point ) ); some_point.print_coordinates( &some_point ); puts( "\n" ); print_name( d3_point_to_base_iface( &d3_null_point ) ); print_size( d3_point_to_sizible_iface( &d3_null_point ) ); d3_null_point.print_coordinates( &d3_null_point ); puts( "\n" ); print_name( d3_point_to_base_iface( &d3_some_point ) ); print_size( d3_point_to_sizible_iface( &d3_some_point ) ); d3_some_point.print_coordinates( &d3_some_point ); puts( "\nPress any key to exit...\n" ); getchar(); return 0; }