In a single-threaded application I use code like this:
Interface
function GetNextUID : integer;
Implementation
function GetNextUID : integer;
const
cUID : integer = 0;
begin
inc( cUID );
result := cUID;
end;
This could of course be implemented as a singleton object, etc. - I'm just giving the simplest possible example.
Q: How can I modify this function (or design a class) to achieve the same result safely from concurrent threads?
You can use the Interlocked*
functions:
function GetNextUID : integer;
{$J+} // Writeble constants
const
cUID : integer = 0;
begin
Result := InterlockedIncrement(cUID);
end;
More modern Delphi versions have renamed these methods into Atomic*
(like AtomicDecrement
, AtomicIncrement
, etc), so the example code becomes this:
function GetNextUID : integer;
{$J+} // Writeble constants
const
cUID : integer = 0;
begin
Result := AtomicIncrement(cUID);
end;