Delphi TSemaphore source code

Question

I'm looking to make a thread pool. I have found a couple of examples on line, but they use TSemaphore in the SyncObjs library.

I'm using Delphi 6 and my SyncObjs doesn't include TSemaphore. I've looked around the net and can't find any source code for it.

Is there a library that works with Delphi 6 that includes TSemaphore?

Answer 1

The TSemaphore class is a simple wrapper around the Win32 semaphore API. It is very easy to create a simple wrapper in the same style. For example:

type
  TSemaphore = class
  private
    FHandle: THandle;
  public
    constructor Create(AInitialCount, AMaximumCount: Integer);
    destructor Destroy; override;
    procedure Acquire;
    function Release(AReleaseCount: Integer): Integer; overload;
    procedure Release; overload;
  end;

constructor TSemaphore.Create(AInitialCount, AMaximumCount: Integer);
begin
  inherited Create;
  FHandle := CreateSemaphore(nil, AInitialCount, AMaximumCount, nil);
  Win32Check(FHandle <> 0);
end;

destructor TSemaphore.Destroy;
begin
  if FHandle <> 0 then
    CloseHandle(FHandle);
  inherited;
end;

procedure TSemaphore.Acquire;
begin
  Win32Check(WaitForSingleObject(FHandle, INFINITE) = WAIT_OBJECT_0);
end;

function TSemaphore.Release(AReleaseCount: Integer): Integer;
begin
  Win32Check(ReleaseSemaphore(FHandle, AReleaseCount, @Result));
end;

procedure TSemaphore.Release;
begin
  Release(1);
end;

This is about as simple as can be. Starting from this you should be able to add any bells and whistles that you need.

Note that I have not tested this, so please don't blindly copy it without trying to understand it.