IDL get variable size in bytes

There is ways to get the actual size (byte) of the IDL variables.

1. Use built-in size function

FUNCTION sizeof, DataItem


;
; First get the information regarding the item
;
Info = SIZE (DataItem)


;
; Deduce type and number of elements
;
Type = info (info (0) +1)
Nitems = info (info (0) +2)
Size = 0


;
; Calculate number of bytes depending on item type
;
Case Type of


1:size = 1 * nitems


2:size = 2 * nitems


3:size = 4 * nitems


4:size = 4 * nitems


5:size = 8 * nitems


6:size = 8 * nitems


7:size = 1 * nitems


8:begin
Tags = Tag_names (DataItem)
Info1 = SIZE (Tags)
For j = 0, Info1 (Info1 (0) +2)-1 do BEGIN
String = "size = size + sizeof (DataItem." + Tags (j) + ")"
ret = EXECUTE (String)
ENDfor
END


Endcase


;
; Return size in bytes
;
RETURN, LONG (Size)


END

2. Use the structure information

Structure = {Variable:variable}

Help, Structure

The prompt would print out the actual number of bytes that variable Occupys.