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{************************************************************************}
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{ }
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{ Borland Delphi Visual Component Library }
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{ InterBase Express core components }
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{ }
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{ Copyright (c) 1998-2000 Inprise Corporation }
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{ }
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{ InterBase Express is based in part on the product }
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{ Free IB Components, written by Gregory H. Deatz for }
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{ Hoagland, Longo, Moran, Dunst & Doukas Company. }
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{ Free IB Components is used under license. }
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{ }
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{ The contents of this file are subject to the InterBase }
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{ Public License Version 1.0 (the "License"); you may not }
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{ use this file except in compliance with the License. You }
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{ may obtain a copy of the License at http://www.Inprise.com/IPL.html }
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{ Software distributed under the License is distributed on }
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{ an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either }
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{ express or implied. See the License for the specific language }
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{ governing rights and limitations under the License. }
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{ The Original Code was created by InterBase Software Corporation }
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{ and its successors. }
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{ Portions created by Inprise Corporation are Copyright (C) Inprise }
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{ Corporation. All Rights Reserved. }
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{ Contributor(s): Jeff Overcash }
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{ }
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{ IBX For Lazarus (Firebird Express) }
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{ Contributor: Tony Whyman, MWA Software http://www.mwasoftware.co.uk }
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{ Portions created by MWA Software are copyright McCallum Whyman }
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{ Associates Ltd 2011 }
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{ }
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{************************************************************************}
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{
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This unit has been almost completely re-written as the original code was
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not that robust - and I am not even sure if it worked. The IBPP C++ implementation
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was used for guidance and inspiration. A permanent thread is used to receive
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events from the asynchronous event handler. This then uses "Synchronize" to
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process the event in the main thread.
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Note that an error will occur if the TIBEvent's Registered property is set to
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true before the Database has been opened.
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}
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unit IBEvents;
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{$Mode Delphi}
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interface
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uses
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{$IFDEF WINDOWS }
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Windows,
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{$ELSE}
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unix,
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{$ENDIF}
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Classes, IBHeader, IBExternals, IB, IBDatabase;
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const
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MaxEvents = 15;
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type
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TEventAlert = procedure( Sender: TObject; EventName: string; EventCount: longint;
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var CancelAlerts: Boolean) of object;
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{ TIBEvents }
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TIBEvents = class(TComponent)
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private
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FIBLoaded: Boolean;
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FBase: TIBBase;
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FEvents: TStrings;
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FOnEventAlert: TEventAlert;
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FEventHandler: TObject;
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FRegistered: boolean;
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FDeferredRegister: boolean;
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procedure EventChange(sender: TObject);
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function GetDatabase: TIBDatabase;
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function GetDatabaseHandle: TISC_DB_HANDLE;
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procedure SetDatabase( value: TIBDatabase);
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procedure ValidateDatabase( Database: TIBDatabase);
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procedure DoBeforeDatabaseDisconnect(Sender: TObject);
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procedure DoAfterDatabaseConnect(Sender: TObject);
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protected
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procedure Notification( AComponent: TComponent; Operation: TOperation); override;
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procedure SetEvents( value: TStrings);
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procedure SetRegistered( value: boolean);
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public
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constructor Create( AOwner: TComponent); override;
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destructor Destroy; override;
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procedure RegisterEvents;
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procedure UnRegisterEvents;
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property DatabaseHandle: TISC_DB_HANDLE read GetDatabaseHandle;
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property DeferredRegister: boolean read FDeferredRegister write FDeferredRegister;
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published
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property Database: TIBDatabase read GetDatabase write SetDatabase;
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property Events: TStrings read FEvents write SetEvents;
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property Registered: Boolean read FRegistered write SetRegistered;
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property OnEventAlert: TEventAlert read FOnEventAlert write FOnEventAlert;
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end;
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implementation
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uses
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IBIntf, syncobjs, SysUtils;
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type
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TEventHandlerStates = (
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stIdle, {Events not monitored}
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stHasEvb, {Event Block Allocated but not queued}
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stQueued, {Waiting for Event}
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stSignalled {Event Callback signalled Event}
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);
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{ TEventHandler }
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TEventHandler = class(TThread)
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private
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FOwner: TIBEvents;
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FCriticalSection: TCriticalSection; {protects race conditions in stQueued state}
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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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FState: TEventHandlerStates;
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FEventBuffer: PChar;
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FEventBufferLen: integer;
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FEventID: ISC_LONG;
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FRegisteredState: Boolean;
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FResultBuffer: PChar;
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FEvents: TStringList;
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FSignalFired: boolean;
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procedure QueueEvents;
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procedure CancelEvents;
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procedure HandleEventSignalled(length: short; updated: PChar);
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procedure DoEventSignalled;
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protected
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procedure Execute; override;
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public
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constructor Create(Owner: TIBEvents);
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destructor Destroy; override;
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procedure Terminate;
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procedure RegisterEvents(Events: TStrings);
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procedure UnregisterEvents;
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end;
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{This procedure is used for the event call back - note the cdecl }
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procedure IBEventCallback( ptr: pointer; length: short; updated: PChar); cdecl;
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begin
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if (ptr = nil) or (length = 0) or (updated = nil) then
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Exit;
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{ Handle events asynchronously in second thread }
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TEventHandler(ptr).HandleEventSignalled(length,updated);
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end;
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{ TEventHandler }
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procedure TEventHandler.QueueEvents;
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var
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callback: pointer;
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DBH: TISC_DB_HANDLE;
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begin
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if FState <> stHasEvb then
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Exit;
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FCriticalSection.Enter;
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try
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callback := @IBEventCallback;
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DBH := FOwner.DatabaseHandle;
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if (isc_que_events( StatusVector, @DBH, @FEventID, FEventBufferLen,
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FEventBuffer, TISC_CALLBACK(callback), PVoid(Self)) <> 0) then
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IBDatabaseError;
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FState := stQueued
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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 TEventHandler.CancelEvents;
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var
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DBH: TISC_DB_HANDLE;
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begin
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if FState in [stQueued,stSignalled] then
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begin
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FCriticalSection.Enter;
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try
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DBH := FOwner.DatabaseHandle;
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if (isc_Cancel_events( StatusVector, @DBH, @FEventID) <> 0) then
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IBDatabaseError;
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FState := stHasEvb;
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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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if FState = stHasEvb then
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begin
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isc_free( FEventBuffer);
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FEventBuffer := nil;
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isc_free( FResultBuffer);
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FResultBuffer := nil;
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FState := stIdle
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end;
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FSignalFired := false
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end;
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procedure TEventHandler.HandleEventSignalled(length: short; updated: PChar);
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begin
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FCriticalSection.Enter;
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try
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if FState <> stQueued then
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Exit;
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Move(Updated[0], FResultBuffer[0], Length);
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FState := stSignalled;
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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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finally
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FCriticalSection.Leave
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end;
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end;
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procedure TEventHandler.DoEventSignalled;
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var
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i: integer;
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CancelAlerts: boolean;
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Status: array[0..19] of ISC_LONG; {Note in 64 implementation the ibase.h implementation
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is different from Interbase 6.0 API documentatoin}
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begin
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if FState <> stSignalled then
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Exit;
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isc_event_counts( @Status, FEventBufferLen, FEventBuffer, FResultBuffer);
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CancelAlerts := false;
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if not FSignalFired then
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FSignalFired := true {Ignore first time}
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else
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if assigned(FOwner.FOnEventAlert) then
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begin
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for i := 0 to FEvents.Count - 1 do
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begin
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try
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if (Status[i] <> 0) and not CancelAlerts then
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FOwner.FOnEventAlert( self, FEvents[i], Status[i], CancelAlerts);
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except
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FOwner.FBase.HandleException(Self)
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end;
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end;
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end;
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FState := stHasEvb;
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if CancelAlerts then
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CancelEvents
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else
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QueueEvents
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end;
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procedure TEventHandler.Execute;
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begin
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while not Terminated do
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begin
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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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{$ENDIF}
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if not Terminated and (FState = stSignalled) then
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Synchronize(DoEventSignalled)
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end;
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end;
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constructor TEventHandler.Create(Owner: TIBEvents);
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var
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PSa : PSecurityAttributes;
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{$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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{$ELSE}
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begin
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PSa:= nil;
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{$ENDIF}
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inherited Create(true);
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FOwner := Owner;
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FState := stIdle;
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FCriticalSection := TCriticalSection.Create;
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{$IFDEF WINDOWS}
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FEventHandler := CreateEvent(PSa,false,true,nil);
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{$ELSE}
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FEventWaiting := TEventObject.Create(PSa,false,true,FOwner.Name+'.Events');
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{$ENDIF}
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FEvents := TStringList.Create;
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FreeOnTerminate := true;
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Resume
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end;
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destructor TEventHandler.Destroy;
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begin
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if assigned(FCriticalSection) then FCriticalSection.Free;
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{$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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if assigned(FEvents) then FEvents.Free;
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inherited Destroy;
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end;
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procedure TEventHandler.Terminate;
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begin
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inherited Terminate;
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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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CancelEvents;
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end;
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procedure TEventHandler.RegisterEvents(Events: TStrings);
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var
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i: integer;
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EventNames: array of PChar;
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begin
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UnregisterEvents;
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if Events.Count = 0 then
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exit;
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setlength(EventNames,MaxEvents);
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try
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for i := 0 to Events.Count-1 do
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EventNames[i] := PChar(Events[i]);
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FEvents.Assign(Events);
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FEventBufferlen := isc_event_block(@FEventBuffer,@FResultBuffer,
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Events.Count,
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EventNames[0],EventNames[1],EventNames[2],
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EventNames[3],EventNames[4],EventNames[5],
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EventNames[6],EventNames[7],EventNames[8],
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EventNames[9],EventNames[10],EventNames[11],
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EventNames[12],EventNames[13],EventNames[14]
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);
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FState := stHasEvb;
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FRegisteredState := true;
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QueueEvents
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finally
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SetLength(EventNames,0)
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end;
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end;
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procedure TEventHandler.UnregisterEvents;
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begin
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if FRegisteredState then
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begin
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CancelEvents;
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FRegisteredState := false;
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end;
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end;
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{ TIBEvents }
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procedure TIBEvents.ValidateDatabase( Database: TIBDatabase);
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begin
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if not assigned( Database) then
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IBError(ibxeDatabaseNameMissing, [nil]);
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if not Database.Connected then
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IBError(ibxeDatabaseClosed, [nil]);
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end;
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constructor TIBEvents.Create( AOwner: TComponent);
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begin
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inherited Create( AOwner);
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FIBLoaded := False;
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CheckIBLoaded;
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FIBLoaded := True;
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FBase := TIBBase.Create(Self);
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FBase.BeforeDatabaseDisconnect := DoBeforeDatabaseDisconnect;
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FBase.AfterDatabaseConnect := DoAfterDatabaseConnect;
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FEvents := TStringList.Create;
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with TStringList( FEvents) do
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begin
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OnChange := EventChange;
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Duplicates := dupIgnore;
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end;
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FEventHandler := TEventHandler.Create(self)
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end;
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destructor TIBEvents.Destroy;
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begin
|
408 |
if FIBLoaded then
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begin
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UnregisterEvents;
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SetDatabase(nil);
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TStringList(FEvents).OnChange := nil;
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FBase.Free;
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FEvents.Free;
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end;
|
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if assigned(FEventHandler) then
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417 |
TEventHandler(FEventHandler).Terminate;
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FEventHandler := nil;
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inherited Destroy;
|
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end;
|
421 |
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|
423 |
|
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procedure TIBEvents.EventChange( sender: TObject);
|
425 |
begin
|
426 |
{ check for blank event }
|
427 |
if TStringList(Events).IndexOf( '') <> -1 then
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428 |
IBError(ibxeInvalidEvent, [nil]);
|
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{ check for too many events }
|
430 |
if Events.Count > MaxEvents then
|
431 |
begin
|
432 |
TStringList(Events).OnChange := nil;
|
433 |
Events.Delete( MaxEvents);
|
434 |
TStringList(Events).OnChange := EventChange;
|
435 |
IBError(ibxeMaximumEvents, [nil]);
|
436 |
end;
|
437 |
if Registered then
|
438 |
TEventHandler(FEventHandler).RegisterEvents(Events);
|
439 |
end;
|
440 |
|
441 |
procedure TIBEvents.Notification( AComponent: TComponent;
|
442 |
Operation: TOperation);
|
443 |
begin
|
444 |
inherited Notification( AComponent, Operation);
|
445 |
if (Operation = opRemove) and (AComponent = FBase.Database) then
|
446 |
begin
|
447 |
UnregisterEvents;
|
448 |
FBase.Database := nil;
|
449 |
end;
|
450 |
end;
|
451 |
|
452 |
procedure TIBEvents.RegisterEvents;
|
453 |
begin
|
454 |
ValidateDatabase( Database);
|
455 |
if csDesigning in ComponentState then FRegistered := true
|
456 |
else
|
457 |
begin
|
458 |
if not FBase.Database.Connected then
|
459 |
FDeferredRegister := true
|
460 |
else
|
461 |
begin
|
462 |
TEventHandler(FEventHandler).RegisterEvents(Events);
|
463 |
FRegistered := true;
|
464 |
end;
|
465 |
end;
|
466 |
end;
|
467 |
|
468 |
procedure TIBEvents.SetEvents( value: TStrings);
|
469 |
begin
|
470 |
FEvents.Assign( value);
|
471 |
end;
|
472 |
|
473 |
procedure TIBEvents.SetDatabase( value: TIBDatabase);
|
474 |
begin
|
475 |
if value <> FBase.Database then
|
476 |
begin
|
477 |
if Registered then UnregisterEvents;
|
478 |
if assigned( value) and value.Connected then ValidateDatabase( value);
|
479 |
FBase.Database := value;
|
480 |
if (FBase.Database <> nil) and FBase.Database.Connected then
|
481 |
DoAfterDatabaseConnect(FBase.Database)
|
482 |
end;
|
483 |
end;
|
484 |
|
485 |
function TIBEvents.GetDatabase: TIBDatabase;
|
486 |
begin
|
487 |
Result := FBase.Database
|
488 |
end;
|
489 |
|
490 |
procedure TIBEvents.SetRegistered( value: Boolean);
|
491 |
begin
|
492 |
FDeferredRegister := false;
|
493 |
if not assigned(FBase) or (FBase.Database = nil) then
|
494 |
begin
|
495 |
FDeferredRegister := value;
|
496 |
Exit;
|
497 |
end;
|
498 |
|
499 |
if value then RegisterEvents else UnregisterEvents;
|
500 |
end;
|
501 |
|
502 |
procedure TIBEvents.UnregisterEvents;
|
503 |
begin
|
504 |
FDeferredRegister := false;
|
505 |
if not FRegistered then
|
506 |
Exit;
|
507 |
if csDesigning in ComponentState then
|
508 |
FRegistered := false
|
509 |
else
|
510 |
begin
|
511 |
TEventHandler(FEventHandler).UnRegisterEvents;
|
512 |
FRegistered := false;
|
513 |
end;
|
514 |
end;
|
515 |
|
516 |
procedure TIBEvents.DoBeforeDatabaseDisconnect(Sender: TObject);
|
517 |
begin
|
518 |
UnregisterEvents;
|
519 |
end;
|
520 |
|
521 |
procedure TIBEvents.DoAfterDatabaseConnect(Sender: TObject);
|
522 |
begin
|
523 |
if FDeferredRegister then
|
524 |
Registered := true
|
525 |
end;
|
526 |
|
527 |
function TIBEvents.GetDatabaseHandle: TISC_DB_HANDLE;
|
528 |
begin
|
529 |
ValidateDatabase(FBase.Database);
|
530 |
Result := FBase.Database.Handle;
|
531 |
end;
|
532 |
|
533 |
|
534 |
end.
|