Save any type of variable to array of byte

[bastla]

Hello together,

as I understand variables, they're nothing else than bytes. So I had that awsome idea to store any value into an array of bytes.

I created a class named "TValue" and it contains the array of byte named "value". This is how I store variables to the array of bytes:

Code: [Select]

procedure TValue.store(const any);
begin
  SetLength(self.value, 0);
  SetLength(self.value, SizeOf(any));
  Move(any, self.value, SizeOf(any));
end;
My function to convert this bytes back to an integer looks like this:

Code: [Select]

function TValue.Integer: integer;
begin
   Move(self.value, Result, SizeOf(value));
end;
But this doesn't work, I get "0" as output, whatever integer variable I use for "any"...
I actually do not know what I'm doing wrong, I would appreciate your help!

Thanks in advance and greetings,
bastla

[ausdigi]

You are actually changing the array variable pointer rather than its elements - you need to pass in its first element. The compiler was thinking you wanted to copy the address of the array rather than the array. Looking at the changes happen in the debugger might have helped. Check my modifications below.

Code: [Select]

procedure TValue.store(const any);
begin
  //superfluous SetLength(self.value, 0);
  SetLength(self.value, SizeOf(any));
  Move(any, self.value[0], SizeOf(any));
end;

function TValue.Integer: integer;
begin
   Move(self.value[0], Result, SizeOf(value));
end;

[engkin]

Regarding SizeOf, I don't think it works. According to its documentation:

...Its result is calculated at compile-time, and hard-coded in the executable.

[taazz]

Well lets start by the the fact the parameter any is an untyped parameter untyped parameters have no size and you can not access them directly. The only thing that works on them is the address operator or passing them to other function that accepts untyped parameters. there for sizeof should always be 0 in your case and it should not return anything that is not there when you call the method.
References.
http://www.freepascal.org/docs-html/ref/refsu59.html#x158-16800014.4.2
http://forum.lazarus.freepascal.org/index.php/topic,16434.msg89190.html#msg89190

[howardpc]

Seems to me you're trying to reinvent the wheel, which is already implemented in the compiler and RTL, and can be utilised with simple declarations of this sort:

Code: [Select]

var
 v:variant;


[sam707]

@howardpc

I agree : using variants plus TMemoryStream is the original wheel that sounds to be reinvented here