interface
type
  TMessage = record
    Something...
  end;
 
  PEntry = ^TEntry;
  TEntry = record
    Message: TMessage;
    Next: PEntry;
  end;
 
  TMessageQueue = class(TObject)
  private
    FHead: PEntry;
    FTail: PEntry;
    FCount: Integer;
  public
    constructor Create;
    destructor Destroy; override;
    procedure Push(Message: TMessage);
    function  Pop(): TMessage;
    property Count: Integer read FCount;
  end;
 
implementation
 
constructor TMessageQueue.Create;
begin
  FHead := nil;
  FTail := nil;
  FCount := 0;
end;
 
destructor TMessageQueue.Destroy;
var
  temp: PEntry;
begin
  while true do
  begin
    if FHead = nil then Break;
    temp := FHead.Next;
    Dispose(FHead);
    FHead := temp;
  end;
end;
 
procedure TMessageQueue.Push(Message: TMessage);
begin
  if FHead = nil then
  begin
    New(FHead);
    FHead.Message := Message;
    FHead.Next := nil;
    FTail := FHead;
  end
  else
  begin
    New(FTail.Next);
    FTail := FTail.Next;
    FTail.Next := nil;
    FTail.Message := Message;
  end;
  Inc(FCount);
end;
 
function TMessageQueue.Pop(): TMessage;
var
  temp: PEntry;
begin
  if FHead = nil then Assert(false)
  else
  begin
    Dec(FCount);
    Result := FHead.Message;
    temp := FHead.Next;
    Dispose(FHead);
    FHead := temp;
  end;
end;