OpenEuphoria

1. Testing atoms if pointer

• Posted by RStowasser Aug 16, 2010
• 1309 views

Is there a built-in function in Euphoria 4 to test if an atom is a pointer? In the moment in Windows I use the isBadxxxPtr functions to test a value e.g.

include std/dll.e 
include std/machine.e 
include std/text.e 
include std/console.e 
 
constant Kernel32 = open_dll("kernel32.dll") 
 
-- checking if read access 
 
constant isBadReadptr = define_c_func(Kernel32, "IsBadReadPtr", {C_LONG, C_LONG}, C_INT) 
------------------------------------------------------------ 
 
function is_ptr(object a) 
   -- simple check 
   if sequence(a) then 
      return 0 
   end if 
   if c_func(isBadReadptr, {a,1} ) then 
      return 0 
   end if 
   return 1 
end function 
 
procedure check_ptr(object item) 
    puts(1, "item = " & sprint(item)) 
    if is_ptr(item) then 
       puts(1, ", is pointer address\n") 
    else 
       puts(1, ", is not a pointer\n") 
    end if 
end procedure 
 
atom a = 1      check_ptr(a) 
a = allocate(4) check_ptr(a) 
free(a)         --check_ptr(a) 
a = 10          check_ptr(a) 
a = 'a'         check_ptr(a) 
a = allocate_string("This is a string") check_ptr(a) 
free(a) 
a = -1          check_ptr(a) 
 
sequence s = "Hello"    check_ptr(s) 
 
display("Enter a key to end ...") 
if wait_key() then end if 
 

Maybe there is a more general test available now for the Windows and Unix families?

Roland

3. Re: Testing atoms if pointer

• Posted by RStowasser Aug 16, 2010
• 1319 views

Hi Matt,

thank you for the link. These were impressive and convincing arguments. So probably there is no simple solution to find out if I had allocated memory to an atom?

Roland

5. Re: Testing atoms if pointer

• Posted by RStowasser Aug 16, 2010
• 1279 views

Currently I am experimenting with the Iup dlls and trying to wrap functions with variable arguments. Basically I am doing this in a similar way like this (a little bit simplified):

Ihandle* IupHbox(Ihandle *child, ...); [in C]

--constant hIupHbox = def_c_func(hIup, "IupHbox", {P}, P) 
object hIupHbox 
public function IupHbox(sequence child) 
    -- returns id of created element, or NULL if error 
    hIupHbox = -1 
    sequence c_args = {} 
    for x = 1 to length(child) do 
    	c_args &= P 
    end for 
 
    hIupHbox = define_c_func(hIup, "IupHbox", c_args, P) 
     
    Ihandle id_element = c_func(hIupHbox, child) 
    if id_element = NULL then crash("something wrong with IupHbox") end if 
    return id_element 
end function 

This is a relative simple example. But there are some functions in the Iup library in which case I am not sure if I always can use C_POINTER. So I wondered if there would be a simple check to see if an arguement in the sequence is a pointer or a value.

Roland