size of variant records

[440bx]

Hello,

Does FPC provide a way to determine the size of a variant record up to and including a specific field/variant ?

For instance, in the following sample:

Code: Pascal  [Select][+][-]

1. {$APPTYPE CONSOLE}
2.  
3. type
4.   TSOME_VARIANT_TYPE = record
5.     VariantSize          : DWORD;
6.  
7.     SomeField            : qword;
8.  
9.     case integer of
10.       1 : (
11.            a : byte;
12.           );
13.  
14.       2 : (
15.            b : word;
16.           );
17.  
18.       3 : (
19.            c : DWORD;
20.           );
21.  
22.       4 : (
23.            d : qword;
24.           );
25.   end;
26.  
27. var
28.   Size : DWORD;
29.  
30. begin
31.  
32.   { how to get the size up to and including field a or b or c ?               }
33.  
34.   { Size := ???                                                               }
35. end.

Is there a way to determine the size of the record up to and including a (but not b, c and d) ? or upto and including b (or c) excluding the fields that follow it ?

Thank you for your help.

[engkin]

Add the offset of the field to the SizeOf the field?

[440bx]

Add the offset of the field to the SizeOf the field?

Yes, that will do it.  I was hoping for something like "SizeTo(<Record.Fieldname>);  Can't have it all, I guess

Thank you for the suggestion.  At least it tells me that there isn't a really straightforward/direct way of getting the size up to some field.

[engkin]

On a positive note, it is a compile-time value.

[PascalDragon]

Add the offset of the field to the SizeOf the field?

Yes, that will do it.  I was hoping for something like "SizeTo(<Record.Fieldname>);  Can't have it all, I guess

Thank you for the suggestion.  At least it tells me that there isn't a really straightforward/direct way of getting the size up to some field.

Well, the size up to some field is the offset of that field

[440bx]

Well, the size up to some field is the offset of that field

Wouldn't it be the offset to the _next_ field ? (which makes the expression to calculate the size a bit confusing)

[PascalDragon]

Well, the size up to some field is the offset of that field

Wouldn't it be the offset to the _next_ field ? (which makes the expression to calculate the size a bit confusing)

Right, forgot that you meant including the field