Reallocating/resizing Lua 5.1 userdata in C -

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how resize lua 5.1 userdata object in c during runtime?

i change size of numarray structure described in roberto ierusalimschy's book programming in lua, 2nd edition, pp. 260, lua 5.1 console.

my numarray userdata can either store unsigned chars or lua_numbers. played around calling unmodified luam_realloc_ function defined in lmem.c, call c's realloc (via l_alloc) function returns null, not enough memory error message.

would please me ?

--- lapi.c -------------------------------------------------------------------------------------------------  lua_api void *agn_resizeud (lua_state *l, void *block, size_t osize, size_t nsize) {   udata *u = (udata *)luam_realloc_(l, block, osize + sizeof(udata), nsize + sizeof(udata));   u->uv.len = nsize;   if (u == null)     lual_error(l, "error in " lua_qs ": failed allocate memory.", "api/agn_resizeud");   return u; }  --- numarray.c ---------------------------------------------------------------------------------------------  #define checkarray(l, n) (numarray *)lual_checkudata(l, n, "numarray")  [...]  /* auxiliary c function call luam_realloc_ via lua c api */  void *reallocud (lua_state *l, void *block, size_t o, size_t n, size_t sizeofelem, size_t sizeofnumarray) {   if (n + 1 > max_sizet/sizeofelem)     lual_error(l, "error in " lua_qs ": memory allocation error: block big.", "(reallocud)", n);   else     return agn_resizeud(l, block, sizeofnumarray + o*sizeofelem, sizeofnumarray + n*sizeofelem); }  /* function resize numarray */  static int numarray_resize (lua_state *l) {   size_t i;   global_state *g = g(l);   numarray *a = checkarray(l, 1);   int n = lual_checkinteger(l, 2);   if (n < 1)     lual_error(l, "error in " lua_qs ": new size %d non-positive.", "numarray.resize", n);   if (n == a->size) {   /* nothing , not complain */     lua_pushinteger(l, a->size);     return 1;   }   if (n > a->size) {  /* extend */     = reallocud(l, a, a->size, n, a->isnumber ? sizeof(lua_number) : sizeof(char), sizeof(numarray));     if (a->isnumber) {       (i=a->size; < n; i++) a->data.n[i] = 0;     } else {       (i=a->size; < n; i++) a->data.c[i] = 0;     }   } else {  /* reduce */     if (a->isnumber) {       (i=a->size - 1; > n - 1; i--) a->data.n[i] = 0;     } else {       (i=a->size - 1; > n - 1; i--) a->data.c[i] = 0;     }     = reallocud(l, a, a->size, n, a->isnumber ? sizeof(lua_number) : sizeof(char), sizeof(numarray));   }   a->size = n;   lua_pushnumber(l, a->size);   return 1; }  [...]  typedef struct numarray {   size_t size;           /* number of slots */   char isnumber;   union data {     lua_number n[1];  /* pointer various lua_number values */     unsigned char c[1];   } data; } numarray;

there no need mess internals of lua.

but need change how userdata created: instead of allocating struct , data in same memory block, allocate them separately, using lua_newuserdata allocate struct , malloc allocate data.

then, resize data part, update size in struct , realloc data part.


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