From Free Pascal wiki
Revision as of 12:25, 3 July 2021 by Kai Burghardt (talk | contribs) (use proper singular of data)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigationJump to search

Deutsch (de) English (en)

The compiler intrinsic function bitSizeOf returns the size of a datum in bits.


BitSizeOf produces different results only for members of bitpacked structures. In all other cases the result of bitSizeOf is simply 8 * sizeOf(x) (or sizeOf(x) shl 3). To put this relation in other words:

[math]\displaystyle{ \texttt{sizeOf}(\texttt{x}) = \lceil \, \texttt{bitSizeOf}(\texttt{x}) \; / \; 8 \, \rceil }[/math]


In some cases using bitSizeOf can improve your code’s readability:

program binaryPrint(input, output, stdErr);
	(* in FPC `integer` definition *)
	(* depends on the selected mode *)
	i: integer;
	writeLn(binStr(i, bitSizeOf(i)));

If your code makes presumptions about memory requirements, e. g. by using an algorithm exploiting certain properties of your bitpacked data type, you may want to safeguard your code with some conditional compilation, may be even just for documentation purposes.

see also