.一个堆栈类的实现(原创)

unit sfStacks;interface{$DEFINE MULTI_THREAD_QUEUE} //线程安全版本{$IFDEF MULTI_THREAD_QUEUE}uses    Windows;{$ENDIF}type  TsfStack=class  private    FStackSize:Integer;    FBuff:Pointer;  {$IFDEF MULTI_THREAD_QUEUE}    FCS:TRTLCriticalSection;  {$ENDIF}    FPosition:Integer;  protected    procedure Lock();    procedure UnLock();  public    constructor Create(StackSize:Integer=1024);    destructor  Destroy();override;    //\    function Push(AItem: Pointer): Integer;virtual;    function Pop(): Pointer;virtual;  public    property Size:Integer read FStackSize;    property Position:Integer read FPosition;  end;implementation{ TsfQueue }constructor TsfStack.Create(StackSize:Integer);begin  {$IFDEF MULTI_THREAD_QUEUE}     InitializeCriticalSection(FCS);  {$ENDIF}  if StackSize < 1024 then StackSize := 1024;  GetMem(FBuff,StackSize * 4);  ZeroMemory(FBuff,StackSize * 4);  FStackSize := StackSize;  FPosition := 0;end;destructor TsfStack.Destroy;begin  FreeMem(FBuff);  //\  {$IFDEF MULTI_THREAD_QUEUE}     DeleteCriticalSection(FCS);  {$ENDIF}  inherited;end;procedure TsfStack.Lock;begin  {$IFDEF MULTI_THREAD_QUEUE}     EnterCriticalSection(FCS);  {$ENDIF}end;procedure TsfStack.UnLock;begin  {$IFDEF MULTI_THREAD_QUEUE}      LeaveCriticalSection(FCS);  {$ENDIF}end;function TsfStack.Pop: Pointer;var  P:PInteger;begin  Lock();  try    if Position > 0 then    begin      P := FBuff;      Dec(FPosition);      Inc(P,FPosition);      Result := Pointer(P^);    end    else      Result := nil;  finally    UnLock();  end;end;function TsfStack.Push(AItem: Pointer): Integer;var  P:PInteger;begin  Lock();  try    if Position <= Size - 1 then    begin      P := FBuff;      Inc(P,Position);      P^ := Integer(AItem);      Inc(FPosition);      Result := Position;    end    else      Result := -1;  finally    UnLock();  end;end;end.