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{
***************************************************************************
* *
* This source is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
* This code is distributed in the hope that it will be useful, but *
* WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* General Public License for more details. *
* *
* A copy of the GNU General Public License is available on the World *
* Wide Web at <http://www.gnu.org/copyleft/gpl.html>. You can also *
* obtain it by writing to the Free Software Foundation, *
* Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1335, USA. *
* *
***************************************************************************
Abstract:
Demo to show, how a Thread waits for another.
}
unit WaitForUnit1;
{$mode objfpc}{$H+}
interface
uses
Classes, SysUtils, Forms, Controls, Graphics, Dialogs, Buttons,
StdCtrls, LCLProc;
type
{ TBaseThread }
TBaseThread = class(TThread)
public
procedure Log(const Msg: string; AppendLineEnd: boolean = true);
end;
{ TThreadA }
TThreadA = class(TBaseThread)
public
WaitForB: PRtlEvent;
procedure Execute; override;
end;
{ TThreadB }
TThreadB = class(TBaseThread)
private
FCounter: integer;
public
procedure Execute; override;
property Counter: integer read FCounter write FCounter;
end;
{ TForm1 }
TForm1 = class(TForm)
Button1: TButton;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
private
ACriticalSection: TRTLCriticalSection;
MsgText: string;
procedure AddMessage;
public
ThreadA: TThreadA;
ThreadB: TThreadB;
end;
var
Form1: TForm1;
implementation
{$R *.lfm}
{ TForm1 }
procedure TForm1.Button1Click(Sender: TObject);
begin
if ThreadA=nil then
ThreadA:=TThreadA.Create(false);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
InitCriticalSection(ACriticalSection);
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
DoneCriticalsection(ACriticalSection);
end;
procedure TForm1.AddMessage;
begin
Memo1.Lines.Text:=MsgText;
end;
{ TThreadA }
procedure TThreadA.Execute;
begin
Form1.ThreadB:=TThreadB.Create(false);
// create event
WaitForB:=RTLEventCreate;
while not Application.Terminated do begin
Log('A: wait for B ...');
// wait infinitely (until B wakes A)
RtlEventWaitFor(WaitForB);
Log('A: ThreadB.Counter='+IntToStr(Form1.ThreadB.Counter));
end;
end;
{ TThreadB }
procedure TThreadB.Execute;
var
i: Integer;
begin
Counter:=0;
while not Application.Terminated do begin
Log('B: Working ...');
for i:=1 to 5 do begin
Sleep(300);
Log('..... ',false);
end;
Log('');
Counter := Counter + 1;
Log('B: Wake A');
// wake A
RtlEventSetEvent(Form1.ThreadA.WaitForB);
end;
end;
{ TBaseThread }
procedure TBaseThread.Log(const Msg: string; AppendLineEnd: boolean);
var
s: String;
begin
EnterCriticalsection(Form1.ACriticalSection);
s:=Msg;
if AppendLineEnd then
s:=s+LineEnding;
dbgout(s);
Form1.MsgText:=Form1.MsgText+s;
Synchronize(@Form1.AddMessage);
LeaveCriticalsection(Form1.ACriticalSection);
end;
end.
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