/
usemaphore.pas
127 lines (108 loc) · 2.23 KB
/
usemaphore.pas
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unit uSemaphore;
{$mode objfpc}{$H+}
{$OPTIMIZATION OFF}
interface
uses
Classes, SysUtils, syncobjs, Contnrs;
type
{ TSemaphore }
TSemaphore = class
private
fMaxPermits: Cardinal;
fPermits: Cardinal;
fLock: TRTLCriticalSection;
FBlockQueue: Contnrs.TQueue;
function GetWaitCount: Cardinal;
public
procedure Wait;
procedure Post;
function Used: Boolean;
function AttemptWait: Boolean;
constructor Create(MaxPermits: Cardinal);
destructor Destroy; override;
property WaitCount: Cardinal read GetWaitCount;
property Permits: Cardinal read fPermits;
property MaxPermits: Cardinal read fMaxPermits;
end;
implementation
{ TSemaphore }
function TSemaphore.GetWaitCount: Cardinal;
begin
EnterCriticalSection(fLock);
try
Result:= FBlockQueue.Count;
finally
LeaveCriticalSection(fLock);
end;
end;
procedure TSemaphore.Wait;
var
aWait: Boolean;
aEvent: PRTLEvent;
begin
EnterCriticalSection(fLock);
try
if (fPermits > 0) then begin
Dec(fPermits);
aWait:= False;
end else begin
aEvent:= RTLEventCreate;
FBlockQueue.Push(aEvent);
aWait:= True;
end;
finally
LeaveCriticalSection(fLock);
end;
if aWait then begin
RTLeventWaitFor(aEvent);
RTLEventDestroy(aEvent);
end;
end;
function TSemaphore.AttemptWait: Boolean;
begin
Result := True;
EnterCriticalSection(fLock);
try
if (fPermits > 0) then begin
Dec(fPermits);
end else
Result := False;
finally
LeaveCriticalSection(fLock);
end;
end;
procedure TSemaphore.Post;
begin
EnterCriticalSection(fLock);
try
if FBlockQueue.Count > 0 then
RTLEventSetEvent(PRTLEvent(FBlockQueue.Pop))
else
Inc(fPermits);
finally
LeaveCriticalSection(fLock);
end;
end;
function TSemaphore.Used: Boolean;
begin
EnterCriticalSection(fLock);
try
Result := fPermits < fMaxPermits;
finally
LeaveCriticalSection(fLock);
end;
end;
constructor TSemaphore.Create(MaxPermits: Cardinal);
begin
fMaxPermits := MaxPermits;
fPermits := MaxPermits;
InitCriticalSection(fLock);
FBlockQueue:= TQueue.Create;
end;
destructor TSemaphore.Destroy;
begin
DoneCriticalSection(fLock);
FBlockQueue.Free;
inherited Destroy;
end;
end.