unit CSLazy;

interface

uses
  SyncObjs;

type
  ICS = interface
    ['{C1D6A40D-14CA-4E33-8FF7-CD0A01385343}']
    procedure Enter;
    function TryEnter : Boolean;
    procedure Leave;
  end;

function CS( ACS : TCriticalSection ) : ICS;

implementation

type
  TCS = class( TInterfacedObject, ICS )
  private
    FCS : TCriticalSection;
    FEntered : Boolean;
  protected
    procedure Enter;
    function TryEnter : Boolean;
    procedure Leave;
  public
    constructor Create( ACS : TCriticalSection );
    destructor Destroy; override;
  end;

function CS( ACS : TCriticalSection ) : ICS;
begin
  if Assigned( ACS )
  then
    Result := TCS.Create( ACS )
  else
    Result := nil;
end;

{ TCS }

constructor TCS.Create( ACS : TCriticalSection );
begin
  inherited Create;
  FCS := ACS;
end;

destructor TCS.Destroy;
begin
  if FEntered
  then
    FCS.Leave;

  inherited;
end;

procedure TCS.Enter;
begin
  FCS.Enter;
  FEntered := True;
end;

procedure TCS.Leave;
begin
  FCS.Leave;
  FEntered := False;
end;

function TCS.TryEnter : Boolean;
begin
  Result := FCS.TryEnter;
  FEntered := Result;
end;

end.

type
  TMyThread = class( TThread )
  private
    FCS : TCriticalSection;
    FValue : string;
    function GetValue : string;
    procedure SetValue( const Value : string );
  public
    property Value : string read GetValue write SetValue;
  end;

function TMyThread.GetValue : string;
begin
  CS( FCS ).Enter;
  Result := FValue;
end;

procedure TMyThread.SetValue( const Value : string );
begin
  CS( FCS ).Enter;
  FValue := Value;
end;