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{
* This Source Code Form is subject to the terms of the Mozilla Public License,
* v. 2.0. If a copy of the MPL was not distributed with this file, You can
* obtain one at http://mozilla.org/MPL/2.0/
*
* Copyright (C) 2013, Peter Johnson (www.delphidabbler.com).
*
* $Rev$
* $Date$
*
* Implements a class that manages the lifetime of a group of thread objects.
}
unit UThreadGroup;
interface
uses
Classes, Generics.Collections;
type
/// <summary>Class that manages the lifetime of a group of thread objects.
/// </summary>
/// <remarks>
/// <para>Threads should be created suspended (not enforced).</para>
/// <para>Threads must not automatically free themselves on termination. Each
/// thread's FreeOnTerminate property will be set False when it is added to
/// the group.</para>
/// </remarks>
TThreadGroup = class(TObject)
strict private
var
/// <summary>List if threads.</summary>
fThreads: TList<TThread>;
/// <summary>Read accessor for Threads[] property.</summary>
function GetThread(Idx: Integer): TThread;
public
/// <summary>Constructs a new empty thread group object.</summary>
constructor Create;
/// <summary>Destroys object instance.</summary>
destructor Destroy; override;
/// <summary>Adds the given thread to the group.</summary>
procedure Add(AThread: TThread); overload;
/// <summary>Adds each thread in the given array to the group.</summary>
procedure Add(const AThreads: array of TThread); overload;
/// <summary>Notifies all threads to terminate.</summary>
/// <remarks>Simply sets each thread's Terminate property True.</remarks>
procedure Terminate;
/// <summary>Starts all threads.</summary>
/// <remarks>Threads are started in the order they were added.</remarks>
procedure Start;
/// <summary>Waits for each thread to terminate, subject to a timeout.
/// </summary>
/// <param name="Timeout">Cardinal [in] Timeout in ms.</param>
/// <returns>Cardinal. Values are the same as for the Windows API
/// WaitForMultipleObjects function. In summary, values $00..$79 represent
/// success while values >= $80 are errors.</returns>
/// <remarks>WaitFor must not be called when the group is empty.</remarks>
function WaitFor(Timeout: Cardinal): Cardinal;
/// <summary>Signals each thread to terminate and then waits for them to
/// complete, subject to a timeout.</summary>
/// <param name="Timeout">Cardinal [in] Timeout in ms.</param>
/// <returns>Cardinal. Values are the same as for the Windows API
/// WaitForMultipleObjects function. In summary, values $00..$79 represent
/// success while values >= $80 are errors.</returns>
/// <remarks>Kill must not be called when the group is empty.</remarks>
function Kill(Timeout: Cardinal): Cardinal;
/// <summary>Checks of the group is empty, i.e. contains no threads.
/// </summary>
function IsEmpty: Boolean;
/// <summary>Returns the number of threads in the group.</summary>
function Count: Integer;
/// <summary>Indexed array of threads in the group.</summary>
property Threads[Idx: Integer]: TThread read GetThread; default;
end;
implementation
uses
Windows;
{ TThreadGroup }
procedure TThreadGroup.Add(AThread: TThread);
begin
AThread.FreeOnTerminate := False;
fThreads.Add(AThread);
end;
procedure TThreadGroup.Add(const AThreads: array of TThread);
var
Thread: TThread;
begin
for Thread in AThreads do
Thread.FreeOnTerminate := False;
fThreads.AddRange(AThreads);
end;
function TThreadGroup.Count: Integer;
begin
Result := fThreads.Count;
end;
constructor TThreadGroup.Create;
begin
inherited;
fThreads := TList<TThread>.Create;
end;
destructor TThreadGroup.Destroy;
var
Thread: TThread;
begin
for Thread in fThreads do
Thread.Free; // terminates thread cleanly
fThreads.Free;
inherited;
end;
function TThreadGroup.GetThread(Idx: Integer): TThread;
begin
Result := fThreads[Idx];
end;
function TThreadGroup.IsEmpty: Boolean;
begin
Result := fThreads.Count = 0;
end;
function TThreadGroup.Kill(Timeout: Cardinal): Cardinal;
begin
Assert(not IsEmpty, ClassName + '.Kill: Thread list empty');
Terminate;
Result := WaitFor(Timeout);
end;
procedure TThreadGroup.Start;
var
Thread: TThread;
begin
for Thread in fThreads do
Thread.Start;
end;
procedure TThreadGroup.Terminate;
var
Thread: TThread;
begin
for Thread in fThreads do
Thread.Terminate;
end;
function TThreadGroup.WaitFor(Timeout: Cardinal): Cardinal;
var
I: Integer;
Handles: TArray<THandle>;
begin
Assert(not IsEmpty, ClassName + '.WaitFor: Thread list empty');
SetLength(Handles, fThreads.Count);
for I := 0 to Pred(fThreads.Count) do
Handles[I] := fThreads[I].Handle;
Result := WaitForMultipleObjects(
Length(Handles), @Handles[0], True, Timeout
);
end;
end.
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