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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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{************************************************************************}
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unit IBEvents;
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interface
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uses
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SysUtils, Windows, Messages, Classes, Graphics, Controls,
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Forms, Dialogs, DB, IBHeader, IBExternals, IB, IBDatabase;
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const
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MaxEvents = 15;
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EventLength = 64;
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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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TEventBuffer = array[ 0..MaxEvents-1, 0..EventLength-1] of char;
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TIBEvents = class(TComponent)
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private
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FIBLoaded: Boolean;
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FEvents: TStrings;
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FOnEventAlert: TEventAlert;
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FQueued: Boolean;
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FRegistered: Boolean;
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Buffer: TEventBuffer;
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Changing: Boolean;
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CS: TRTLCriticalSection;
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EventBuffer: PChar;
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EventBufferLen: integer;
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EventID: ISC_LONG;
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ProcessingEvents: Boolean;
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RegisteredState: Boolean;
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ResultBuffer: PChar;
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FDatabase: TIBDatabase;
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procedure SetDatabase( value: TIBDatabase);
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procedure ValidateDatabase( Database: TIBDatabase);
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procedure DoQueueEvents;
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procedure EventChange( sender: TObject);
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procedure UpdateResultBuffer( length: short; updated: PChar);
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protected
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procedure HandleEvent;
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procedure Loaded; override;
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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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function GetNativeHandle: TISC_DB_HANDLE;
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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 CancelEvents;
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procedure QueueEvents;
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procedure RegisterEvents;
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procedure UnRegisterEvents;
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property Queued: Boolean read FQueued;
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published
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property Database: TIBDatabase read FDatabase 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;
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function TIBEvents.GetNativeHandle: TISC_DB_HANDLE;
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begin
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if assigned( FDatabase) and FDatabase.Connected then
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Result := FDatabase.Handle
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else result := nil;
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end;
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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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{ TIBEvents }
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procedure HandleEvent( param: integer); stdcall;
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begin
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{ don't let exceptions propogate out of thread }
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try
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TIBEvents( param).HandleEvent;
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except
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Application.HandleException( nil);
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end;
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end;
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procedure IBEventCallback( ptr: pointer; length: short; updated: PChar); cdecl;
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var
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ThreadID: DWORD;
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begin
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{ Handle events asynchronously in second thread }
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EnterCriticalSection( TIBEvents( ptr).CS);
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TIBEvents( ptr).UpdateResultBuffer( length, updated);
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if TIBEvents( ptr).Queued then
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CloseHandle( CreateThread( nil, 8192, @HandleEvent, ptr, 0, ThreadID));
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LeaveCriticalSection( TIBEvents( ptr).CS);
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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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InitializeCriticalSection( CS);
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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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end;
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destructor TIBEvents.Destroy;
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begin
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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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FEvents.Free;
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DeleteCriticalSection( CS);
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end;
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inherited Destroy;
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end;
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procedure TIBEvents.CancelEvents;
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begin
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if ProcessingEvents then
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IBError(ibxeInvalidCancellation, [nil]);
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if FQueued then
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begin
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try
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{ wait for event handler to finish before cancelling events }
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EnterCriticalSection( CS);
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ValidateDatabase( Database);
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FQueued := false;
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Changing := true;
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if (isc_Cancel_events( StatusVector, @FDatabase.Handle, @EventID) > 0) then
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IBDatabaseError;
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finally
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LeaveCriticalSection( CS);
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end;
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end;
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end;
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procedure TIBEvents.DoQueueEvents;
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var
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callback: pointer;
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begin
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ValidateDatabase( DataBase);
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callback := @IBEventCallback;
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if (isc_que_events( StatusVector, @FDatabase.Handle, @EventID, EventBufferLen,
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EventBuffer, TISC_CALLBACK(callback), PVoid(Self)) > 0) then
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IBDatabaseError;
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FQueued := true;
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end;
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procedure TIBEvents.EventChange( sender: TObject);
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begin
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{ check for blank event }
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if TStringList(Events).IndexOf( '') <> -1 then
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IBError(ibxeInvalidEvent, [nil]);
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{ check for too many events }
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if Events.Count > MaxEvents then
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begin
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TStringList(Events).OnChange := nil;
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Events.Delete( MaxEvents);
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TStringList(Events).OnChange := EventChange;
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IBError(ibxeMaximumEvents, [nil]);
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end;
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if Registered then RegisterEvents;
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end;
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procedure TIBEvents.HandleEvent;
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var
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Status: PStatusVector;
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CancelAlerts: Boolean;
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i: integer;
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begin
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try
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{ prevent modification of vital data structures while handling events }
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EnterCriticalSection( CS);
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ProcessingEvents := true;
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isc_event_counts( StatusVector, EventBufferLen, EventBuffer, ResultBuffer);
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CancelAlerts := false;
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if assigned(FOnEventAlert) and not Changing then
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begin
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for i := 0 to Events.Count-1 do
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begin
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try
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Status := StatusVectorArray;
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if (Status[i] <> 0) and not CancelAlerts then
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FOnEventAlert( self, Events[Events.Count-i-1], Status[i], CancelAlerts);
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except
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Application.HandleException( nil);
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end;
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end;
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end;
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Changing := false;
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if not CancelAlerts and FQueued then DoQueueEvents;
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finally
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ProcessingEvents := false;
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LeaveCriticalSection( CS);
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end;
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end;
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procedure TIBEvents.Loaded;
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begin
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inherited Loaded;
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try
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if RegisteredState then RegisterEvents;
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except
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if csDesigning in ComponentState then
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Application.HandleException( self)
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else raise;
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end;
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end;
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procedure TIBEvents.Notification( AComponent: TComponent;
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Operation: TOperation);
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begin
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inherited Notification( AComponent, Operation);
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if (Operation = opRemove) and (AComponent = FDatabase) then
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begin
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UnregisterEvents;
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FDatabase := nil;
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end;
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end;
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procedure TIBEvents.QueueEvents;
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begin
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if not FRegistered then
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IBError(ibxeNoEventsRegistered, [nil]);
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if ProcessingEvents then
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IBError(ibxeInvalidQueueing, [nil]);
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if not FQueued then
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begin
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try
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{ wait until current event handler is finished before queuing events }
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EnterCriticalSection( CS);
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DoQueueEvents;
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Changing := true;
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finally
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LeaveCriticalSection( CS);
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end;
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end;
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end;
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procedure TIBEvents.RegisterEvents;
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var
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i: integer;
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bufptr: pointer;
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eventbufptr: pointer;
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resultbufptr: pointer;
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buflen: integer;
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begin
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ValidateDatabase( Database);
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if csDesigning in ComponentState then FRegistered := true
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else begin
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UnregisterEvents;
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if Events.Count = 0 then exit;
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for i := 0 to Events.Count-1 do
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StrPCopy( @Buffer[i][0], Events[i]);
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i := Events.Count;
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bufptr := @buffer[0];
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eventbufptr := @EventBuffer;
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resultBufPtr := @ResultBuffer;
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asm
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mov ecx, dword ptr [i]
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mov eax, dword ptr [bufptr]
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@@1:
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push eax
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add eax, EventLength
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loop @@1
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push dword ptr [i]
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push dword ptr [resultBufPtr]
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push dword ptr [eventBufPtr]
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call [isc_event_block]
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mov dword ptr [bufLen], eax
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mov eax, dword ptr [i]
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shl eax, 2
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add eax, 12
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add esp, eax
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end;
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EventBufferlen := Buflen;
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FRegistered := true;
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QueueEvents;
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end;
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end;
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procedure TIBEvents.SetEvents( value: TStrings);
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begin
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FEvents.Assign( value);
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end;
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procedure TIBEvents.SetDatabase( value: TIBDatabase);
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begin
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if value <> FDatabase then
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begin
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UnregisterEvents;
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if assigned( value) and value.Connected then ValidateDatabase( value);
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FDatabase := value;
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end;
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end;
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procedure TIBEvents.SetRegistered( value: Boolean);
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begin
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if (csReading in ComponentState) then
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RegisteredState := value
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else if FRegistered <> value then
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if value then RegisterEvents else UnregisterEvents;
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end;
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procedure TIBEvents.UnregisterEvents;
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begin
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if ProcessingEvents then
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IBError(ibxeInvalidRegistration, [nil]);
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if csDesigning in ComponentState then
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FRegistered := false
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else if not (csLoading in ComponentState) then
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begin
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CancelEvents;
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if FRegistered then
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begin
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isc_free( EventBuffer);
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EventBuffer := nil;
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isc_free( ResultBuffer);
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ResultBuffer := nil;
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end;
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FRegistered := false;
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end;
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end;
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procedure TIBEvents.UpdateResultBuffer( length: short; updated: PChar);
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var
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i: integer;
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begin
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for i := 0 to length-1 do
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ResultBuffer[i] := updated[i];
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end;
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end.
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