c - Delphi - How to pass a 'Type' as a parameter -

i know if possible pass declared type (in case record) function. not ask if not sizeof() function, because can take type parameter.

i'm translating code c , keep close original possible. c program declares pusharray , pushstruct macros. since delphi not have macro support, i'm trying turn them functions.

i've googled bit , seems possible use generic types. function pushstruct<t>(arena : pmemory_arena; dtype : <t>) can use in oop type application.

function pushsize_(arena : pmemory_arena; size : memory_index) : pointer; begin     assert((arena^.used + size) <= arena^.size);     result := arena^.base + arena^.used;     arena^.used := arena^.used + size; end;  function pushstruct(arena : pmemory_arena; dtype : ?) : pointer; begin      result := pushsize_(arena, sizeof(dtype)); end;  function pusharray(arena : pmemory_arena; count: uint32; dtype : ?) : pointer; begin     result := pushsize_(arena, (count)*sizeof(dtype)) end; 

here original c code:

#define pushstruct(arena, type) (type *)pushsize_(arena, sizeof(type)) #define pusharray(arena, count, type) (type *)pushsize_(arena, (count)*sizeof(type)) void * pushsize_(memory_arena *arena, memory_index size) {     assert((arena->used + size) <= arena->size);     void *result = arena->base + arena->used;     arena->used += size;      return(result); } 

the c code isn't passing type function. pre-processor expanding macro , computing size. can see prototype of function:

void *pushsize_(memory_arena *arena, memory_index size) 

since don't have macros in delphi, cannot arrange direct translation. personally, if me not attempt match c code exactly. i'd pass size , leave caller use sizeof. don't think that's terrible burden. still leaves close literal translation – missing convenience macros.

if wanted use generics, so, require use static method. instance:

type   tmyclass = class     class function pushsize(arena: pmemory_arena; size: memory_index): pointer; static;     class function pushstruct<t>(arena: pmemory_arena): pointer; static;   end; .... class function tmyclass.pushsize(arena: pmemory_arena; size: memory_index): pointer; begin   result := ....; end;  class function tmyclass.pushstruct<t>(arena: pmemory_arena): pointer; begin   result := pushsize(arena, sizeof(t)); end; 

if want return typed pointer this:

type   tmyclass<t> = class     type p = ^ t;     class function pushsize(arena: pmemory_arena; size: memory_index): pointer; static;     class function pushstruct(arena: pmemory_arena): p; static;   end; .... class function tmyclass<t>.pushsize(arena: pmemory_arena; size: memory_index): pointer; begin   result := ....; end;  class function tmyclass<t>.pushstruct(arena: pmemory_arena): p; begin   result := pushsize(arena, sizeof(t)); end; 

obviously you'd know name use instead of tmyclass!

i'm not convinced generics fit here because guess wanting literal translation possible. not choose use generics in scenario.