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(*
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* Firebird Interface (fbintf). The fbintf components provide a set of
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* Pascal language bindings for the Firebird API.
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*
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* The contents of this file are subject to the Initial Developer's
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* Public License Version 1.0 (the "License"); you may not use this
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* file except in compliance with the License. You may obtain a copy
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* of the License here:
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*
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* http://www.firebirdsql.org/index.php?op=doc&id=idpl
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*
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* Software distributed under the License is distributed on an "AS
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* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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* implied. See the License for the specific language governing rights
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* and limitations under the License.
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*
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* The Initial Developer of the Original Code is Tony Whyman.
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*
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* The Original Code is (C) 2016 Tony Whyman, MWA Software
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* (http://www.mwasoftware.co.uk).
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*
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* All Rights Reserved.
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*
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* Contributor(s): ______________________________________.
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*
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*)
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unit FB30Events;
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{$IFDEF MSWINDOWS}
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{$DEFINE WINDOWS}
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{$ENDIF}
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{$IFDEF FPC}
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{$mode delphi}
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{$interfaces COM}
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{$ENDIF}
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interface
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uses
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{$IFDEF WINDOWS}Windows, {$ENDIF} Classes, SysUtils, Firebird, IB, FB30ClientAPI, FB30Attachment,
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syncobjs, FBEvents;
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type
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TFB30Events = class;
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{ TEventhandlerInterface }
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TEventhandlerInterface = class(Firebird.IEventCallbackImpl)
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private
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FOwner: TFB30Events;
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FName: AnsiString;
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FRef: integer;
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{$IFDEF WINDOWS}
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{Make direct use of Windows API as TEventObject don't seem to work under
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Windows!}
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FEventHandler: THandle;
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{$ELSE}
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FEventWaiting: TEventObject;
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{$ENDIF}
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public
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constructor Create(aOwner: TFB30Events; aName: AnsiString);
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destructor Destroy; override;
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procedure addRef(); override;
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function release(): Integer; override;
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procedure eventCallbackFunction(length: Cardinal; events: BytePtr); override;
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procedure WaitForEvent;
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procedure CancelWait;
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end;
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{ TFB30Events }
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TFB30Events = class(TFBEvents,IEvents)
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private
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FAttachmentIntf: Firebird.IAttachment;
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FEventHandlerThread: TObject;
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FEventsIntf: Firebird.IEvents;
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FAsyncEventCallback: TEventhandlerInterface;
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FSyncEventCallback: TEventhandlerInterface;
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procedure InternalAsyncWaitForEvent(EventHandler: TEventHandler; EventCallBack: TEventhandlerInterface);
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procedure ReleaseIntf;
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protected
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procedure CancelEvents(Force: boolean = false); override;
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function GetIEvents: IEvents; override;
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public
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constructor Create(DBAttachment: TFB30Attachment; Events: TStrings);
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destructor Destroy; override;
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{IEvents}
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procedure WaitForEvent;
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procedure AsyncWaitForEvent(EventHandler: TEventHandler); override;
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end;
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implementation
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uses FBMessages, FBClientAPI;
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type
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{ TEventHandlerThread }
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TEventHandlerThread = class(TThread)
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private
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FOwner: TFB30Events;
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FEventHandler: TEventhandlerInterface;
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protected
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procedure Execute; override;
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public
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constructor Create(Owner: TFB30Events; EventHandler: TEventhandlerInterface);
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procedure Terminate;
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end;
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constructor TEventhandlerInterface.Create(aOwner: TFB30Events; aName: AnsiString);
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var
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PSa : PSecurityAttributes;
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{$IFDEF WINDOWS}
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Sd : TSecurityDescriptor;
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Sa : TSecurityAttributes;
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begin
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InitializeSecurityDescriptor(@Sd,SECURITY_DESCRIPTOR_REVISION);
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SetSecurityDescriptorDacl(@Sd,true,nil,false);
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Sa.nLength := SizeOf(Sa);
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Sa.lpSecurityDescriptor := @Sd;
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Sa.bInheritHandle := true;
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PSa := @Sa;
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{$ELSE}
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GUID : TGUID;
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begin
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PSa:= nil;
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{$ENDIF}
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inherited Create;
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{$IFDEF WINDOWS}
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FEventHandler := CreateEvent(PSa,false,false,nil);
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{$ELSE}
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CreateGuid(GUID);
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FEventWaiting := TEventObject.Create(PSa,false,false,GUIDToString(GUID));
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{$ENDIF}
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FOWner := aOwner;
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FName := aName;
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addRef;
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end;
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destructor TEventhandlerInterface.Destroy;
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begin
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{$IFDEF WINDOWS}
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CloseHandle(FEventHandler);
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{$ELSE}
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if assigned(FEventWaiting) then FEventWaiting.Free;
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{$ENDIF}
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inherited Destroy;
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end;
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procedure TEventhandlerInterface.addRef;
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begin
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Inc(FRef);
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// writeln(FName,': ref count = ',FRef);
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end;
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function TEventhandlerInterface.release: Integer;
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begin
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Dec(FRef);
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// writeln(FName,': ref count = ',FRef);
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if FRef = 0 then Free;
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Result := FRef;
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end;
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procedure TEventhandlerInterface.eventCallbackFunction(length: Cardinal;
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events: BytePtr);
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begin
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// writeln('TEventhandlerInterface: Event Callback');
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FOwner.FCriticalSection.Enter;
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try
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if FOwner.FResultBuffer <> nil then
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Move(events^, FOwner.FResultBuffer^, Length);
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finally
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FOwner.FCriticalSection.Leave
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end;
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//writeln('TEventhandlerInterface: Set Event Called');
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{$IFDEF WINDOWS}
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SetEvent(FEventHandler);
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{$ELSE}
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FEventWaiting.SetEvent;
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{$ENDIF}
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end;
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procedure TEventhandlerInterface.WaitForEvent;
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begin
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// writeln('TEventhandlerInterface: Start Event Wait');
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{$IFDEF WINDOWS}
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WaitForSingleObject(FEventHandler,INFINITE);
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{$ELSE}
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FEventWaiting.WaitFor(INFINITE);
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{$ENDIF}
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// writeln('TEventhandlerInterface: Event Wait Ends');
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end;
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procedure TEventhandlerInterface.CancelWait;
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begin
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{$IFDEF WINDOWS}
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SetEvent(FEventHandler);
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{$ELSE}
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FEventWaiting.SetEvent;
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{$ENDIF}
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end;
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{ TEventHandlerThread }
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procedure TEventHandlerThread.Execute;
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begin
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while not Terminated do
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begin
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FEventHandler.WaitForEvent;
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if not Terminated then
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FOwner.EventSignaled;
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end;
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end;
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constructor TEventHandlerThread.Create(Owner: TFB30Events;
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EventHandler: TEventhandlerInterface);
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begin
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inherited Create(false);
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FOwner := Owner;
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FEventHandler := EventHandler;
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FreeOnTerminate := true;
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end;
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procedure TEventHandlerThread.Terminate;
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begin
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inherited Terminate;
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FEventHandler.CancelWait;
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end;
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{ TFB30Events }
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procedure TFB30Events.CancelEvents(Force: boolean);
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begin
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FCriticalSection.Enter;
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try
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if not FInWaitState then Exit;
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if FEventsIntf <> nil then
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with Firebird30ClientAPI do
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begin
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FEventsIntf.Cancel(StatusIntf);
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if not Force then
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Check4DataBaseError;
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end;
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FInWaitState := false;
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ReleaseIntf;
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inherited CancelEvents(Force);
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finally
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FCriticalSection.Leave
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end;
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end;
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function TFB30Events.GetIEvents: IEvents;
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begin
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Result := self;
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end;
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procedure TFB30Events.InternalAsyncWaitForEvent(EventHandler: TEventHandler;
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EventCallBack: TEventhandlerInterface);
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begin
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FCriticalSection.Enter;
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try
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if FInWaitState then
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IBError(ibxeInEventWait,[nil]);
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FEventHandler := EventHandler;
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ReleaseIntf;
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with Firebird30ClientAPI do
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begin
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FEventsIntf := FAttachmentIntf.queEvents(
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StatusIntf,EventCallBack,
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FEventBufferLen, BytePtr(FEventBuffer));
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Check4DataBaseError;
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end;
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FInWaitState := true;
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finally
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FCriticalSection.Leave
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end;
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end;
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procedure TFB30Events.ReleaseIntf;
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begin
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if FEventsIntf <> nil then
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FEventsIntf.release;
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FEventsIntf := nil;
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end;
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constructor TFB30Events.Create(DBAttachment: TFB30Attachment; Events: TStrings);
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begin
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inherited Create(DBAttachment,DBAttachment,Events);
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FAttachmentIntf := DBAttachment.AttachmentIntf;
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FSyncEventCallback := TEventhandlerInterface.Create(self,'Sync');
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end;
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destructor TFB30Events.Destroy;
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begin
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CancelEvents(true);
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if assigned(FEventHandlerThread) then
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TEventHandlerThread(FEventHandlerThread).Terminate;
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if assigned(FAsyncEventCallback) then TEventhandlerInterface(FAsyncEventCallback).release;
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if assigned(FSyncEventCallback) then TEventhandlerInterface(FSyncEventCallback).release;
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ReleaseIntf;
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inherited Destroy;
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end;
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procedure TFB30Events.AsyncWaitForEvent(EventHandler: TEventHandler);
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begin
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{Seems like we have to create a new callback object each time to avoid empty events}
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if assigned(FEventHandlerThread) then
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TEventHandlerThread(FEventHandlerThread).Terminate;
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if assigned(FAsyncEventCallback) then TEventhandlerInterface(FAsyncEventCallback).release;
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FAsyncEventCallback := TEventhandlerInterface.Create(self,'Async');
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FEventHandlerThread := TEventHandlerThread.Create(self,FAsyncEventCallback);
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InternalAsyncWaitForEvent(EventHandler,FAsyncEventCallback);
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end;
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procedure TFB30Events.WaitForEvent;
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begin
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InternalAsyncWaitForEvent(nil,FSyncEventCallback);
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FSyncEventCallback.WaitForEvent;
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end;
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end.
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