unit untMain;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    btnStart: TButton;
    procedure btnStartClick(Sender: TObject);
  private
    procedure ThreadsDone(Sender:TObject);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
var
  CS:TRTLCriticalSection; //临界区记录
  hMutex:THandle = 0; //互斥句柄
  hSem:THandle = 0;//信号量句柄
  DoneFlags:Integer = 0;
threadvar//线程局部变量
  GlobalStr:string;
type
  TTLSThread = class(TThread)
    private
      FNewStr:string;
    protected
      procedure Execute;override;
    public
      constructor Create(const ANewStr:string);
  end;

procedure SetShowStr(const S:string);
begin
  if S = '' then
    MessageBox(0,PChar(GlobalStr),'The string is...',MB_OK)
  else
    GlobalStr := S; 
end;

{ TTLSThread }

constructor TTLSThread.Create(const ANewStr: string);
begin
  FNewStr := ANewStr;
  inherited Create(False);
end;

procedure TTLSThread.Execute;
var
  WaitReturn:DWORD;
begin
  OnTerminate := Form1.ThreadsDone; //线程结束时执行相应清理代码
  FreeOnTerminate := True; //自动释放资源
  //EnterCriticalSection(CS); //进入临界区
  WaitReturn := WaitForSingleObject(hSem,INFINITE);//计数器减1
//  if WaitForSingleObject(hMutex,INFINITE)= WAIT_OBJECT_0 then
  if WaitReturn = WAIT_OBJECT_0  then
  begin
    SetShowStr(FNewStr);
    SetShowStr('');
    Sleep(100);
  end;
  //LeaveCriticalSection(CS);//离开临界区
//  ReleaseMutex(hMutex); //解除拥有关系,互斥对象重新进入发信号状态
  ReleaseSemaphore(hSem,1,nil);//信号量对象计数加1
end;

procedure TForm1.btnStartClick(Sender: TObject);
begin
//  InitializeCriticalSection(CS);//初始化临界区
//  hMutex := CreateMutex(nil,False,nil); //创建一个互斥量
  hSem := CreateSemaphore(nil,
    1, //这个值必须在0和lMaximumCount之间，大于0则表示处理发信号状态
    1, //由于只允许个线程进入同步代码，所以设置成1
    nil);//
  SetShowStr('Hello world');
  TTLSThread.Create('Dilbert');
  TTLSThread.Create('xx');
  TTLSThread.Create('test');
end;

procedure TForm1.ThreadsDone(Sender: TObject);
begin
  Inc(DoneFlags);
  if DoneFlags = 3 then  //当前测试时创建了3个线程
  begin
   // DeleteCriticalSection(CS); //删除临界区记录信息
   //CloseHandle(hMutex);//释放由CreateMutex创建对象的句柄
   CloseHandle(hSem);//释放由CreateSemaphore创建对象的句柄
  end;
end;

end.