[英]How do you create a queue of threads in Delphi Xe2?
Have a case where the user may fire off a number of time-consuming jobs that need to be run in the order in which the user does them. 在某些情况下,用户可能会触发许多耗时的工作,这些工作需要按照用户执行工作的顺序运行。
I have been looking at the class TThreadedQueue
to store threads. 我一直在看
TThreadedQueue
类来存储线程。 Is that a good place to start? 那是一个不错的起点吗? Or is there a more appropriate way to do this?
还是有更合适的方法来做到这一点?
below you can find an example of a WorkerThreadPool : 在下面,您可以找到一个WorkerThreadPool的示例:
{~~~~~~~~~~~~~~~~~~~~~~~~~~~~}
Twin_WorkerThreadPool = class;
{~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~}
Twin_WorkerThread = class(TThread)
private
FProc: TProc;
FProcReadySignal: Tevent;
FProcFinishedSignal: Tevent;
protected
procedure Execute; override;
public
constructor Create;
destructor Destroy; override;
procedure ExecuteAndWaitProc(const AProc: TProc);
property ProcFinishedSignal: Tevent read FProcFinishedSignal;
end;
{~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~}
Twin_WorkerThreadPool = class(TObject)
private
fPool: TObjectList<Twin_WorkerThread>;
fSignal: Tevent;
public
constructor Create(const aThreadCount: integer);
destructor Destroy; override;
procedure ExecuteAndWaitProc(const AProc: TProc);
procedure Enqueue(const Value: Twin_WorkerThread);
function Dequeue: Twin_WorkerThread;
end;
{***********************************}
constructor Twin_WorkerThread.Create;
begin
FProc := nil;
FProcReadySignal := TEvent.Create(nil, false{ManualReset}, false, '');
FProcFinishedSignal := TEvent.Create(nil, false{ManualReset}, false, '');
inherited Create(False); // see http://www.gerixsoft.com/blog/delphi/fixing-symbol-resume-deprecated-warning-delphi-2010
end;
{***********************************}
destructor Twin_WorkerThread.Destroy;
begin
Terminate;
FProcReadySignal.setevent;
WaitFor;
ALFreeAndNil(FProcReadySignal);
ALFreeAndNil(FProcFinishedSignal);
inherited;
end;
{**********************************}
procedure Twin_WorkerThread.Execute;
begin
while True do begin
try
//wait the signal
FProcReadySignal.WaitFor(INFINITE);
//if terminated then exit
if Terminated then Break;
//execute fProc
if assigned(FProc) then FProc();
//signal the proc is finished
FProcFinishedSignal.SetEvent;
except
//hide the exception
end;
end;
end;
{*****************************************************************}
procedure Twin_WorkerThread.ExecuteAndWaitProc(const AProc: TProc);
begin
fProc := AProc;
FProcFinishedSignal.ResetEvent;
FProcReadySignal.SetEvent;
FProcFinishedSignal.WaitFor(INFINITE);
fProc := nil;
end;
{********************************************************************}
constructor Twin_WorkerThreadPool.Create(const aThreadCount: integer);
var i: integer;
begin
fPool := TObjectList<Twin_WorkerThread>.create(false{aOwnObjects});
fSignal := TEvent.Create(nil, true{ManualReset}, false, '');
for I := 0 to aThreadCount - 1 do
fPool.Add(Twin_WorkerThread.Create)
end;
{***************************************}
destructor Twin_WorkerThreadPool.Destroy;
var aWorkerThread: Twin_WorkerThread;
i: integer;
begin
for I := 0 to fPool.Count - 1 do begin
aWorkerThread := fPool[i];
fPool[i] := nil;
ALFreeAndNil(aWorkerThread);
end;
ALFreeAndNil(fPool);
ALFreeAndNil(fSignal);
inherited Destroy;
end;
{*********************************************************************}
procedure Twin_WorkerThreadPool.ExecuteAndWaitProc(const AProc: TProc);
var aThread: Twin_WorkerThread;
begin
aThread := Dequeue;
try
aThread.ExecuteAndWaitProc(aProc);
finally
Enqueue(aThread);
end;
end;
{**********************************************************************}
procedure Twin_WorkerThreadPool.Enqueue(const Value: Twin_WorkerThread);
begin
Tmonitor.Enter(fPool);
try
fPool.Add(Value);
if fPool.Count = 1 then fSignal.SetEvent;
finally
Tmonitor.Exit(fPool);
end;
end;
{********************************************************}
function Twin_WorkerThreadPool.Dequeue: Twin_WorkerThread;
begin
Tmonitor.Enter(self); // << only one thread can process the code below
try
Tmonitor.Enter(fPool);
try
if Fpool.Count > 0 then begin
result := fPool[Fpool.Count - 1];
fPool.Delete(Fpool.Count - 1);
exit;
end;
fSignal.ResetEvent;
finally
Tmonitor.Exit(fPool);
end;
while True do begin // << their is a bug on ios with tevent - http://stackoverflow.com/questions/39884521/why-i-get-an-exception-argument-out-of-range
fSignal.WaitFor(Infinite);
Tmonitor.Enter(fPool);
try
if fPool.Count > 0 then begin
result := fPool[Fpool.Count - 1];
fPool.Delete(Fpool.Count - 1);
exit;
end
else begin
{$IFDEF DEBUG}
ALLog('Twin_WorkerThreadPool.Dequeue', 'fSignal.ResetEvent didn''t work as expected!', TalLogType.Error);
{$ENDIF}
end;
finally
Tmonitor.Exit(fPool);
end;
end;
finally
Tmonitor.exit(self);
end;
end;
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