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Comparing ibx/trunk/runtime/IBEvents.pas (file contents):
Revision 31 by tony, Tue Jul 14 15:31:25 2015 UTC vs.
Revision 45 by tony, Tue Dec 6 10:33:46 2016 UTC

#	Line 1 | Line 1
1	<	{************************************************************************}
2	<	{                                                                        }
3	<	{       Borland Delphi Visual Component Library                          }
4	<	{       InterBase Express core components                                }
5	<	{                                                                        }
6	<	{       Copyright (c) 1998-2000 Inprise Corporation                      }
7	<	{                                                                        }
8	<	{    InterBase Express is based in part on the product                   }
9	<	{    Free IB Components, written by Gregory H. Deatz for                 }
10	<	{    Hoagland, Longo, Moran, Dunst & Doukas Company.                     }
11	<	{    Free IB Components is used under license.                           }
12	<	{                                                                        }
13	<	{    The contents of this file are subject to the InterBase              }
14	<	{    Public License Version 1.0 (the "License"); you may not             }
15	<	{    use this file except in compliance with the License. You            }
16	<	{    may obtain a copy of the License at http://www.Inprise.com/IPL.html }
17	<	{    Software distributed under the License is distributed on            }
18	<	{    an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either              }
19	<	{    express or implied. See the License for the specific language       }
20	<	{    governing rights and limitations under the License.                 }
21	<	{    The Original Code was created by InterBase Software Corporation     }
22	<	{       and its successors.                                              }
23	<	{    Portions created by Inprise Corporation are Copyright (C) Inprise   }
24	<	{       Corporation. All Rights Reserved.                                }
25	<	{    Contributor(s): Jeff Overcash                                       }
26	<	{                                                                        }
27	<	{    IBX For Lazarus (Firebird Express)                                  }
28	<	{    Contributor: Tony Whyman, MWA Software http://www.mwasoftware.co.uk }
29	<	{    Portions created by MWA Software are copyright McCallum Whyman      }
30	<	{    Associates Ltd 2011                                                 }
31	<	{                                                                        }
32	<	{************************************************************************}
33	<
34	<	{
35	<	This unit has been almost completely re-written as the original code was
36	<	not that robust - and I am not even sure if it worked. The IBPP C++ implementation
37	<	was used for guidance and inspiration. A permanent thread is used to receive
38	<	events from the asynchronous event handler. This then uses "Synchronize" to
39	<	process the event in the main thread.
40	<
41	<	Note that an error will occur if the TIBEvent's Registered property is set to
42	<	true before the Database has been opened.
43	<	}
44	<
45	<	unit IBEvents;
46	<
47	<	{$Mode Delphi}
48	<
49	<	interface
50	<
51	<	uses
52	<	{$IFDEF WINDOWS }
53	<	Windows,
54	<	{$ELSE}
55	<	unix,
56	<	{$ENDIF}
57	<	Classes, IBHeader, IBExternals, IB, IBDatabase;
58	<
59	<	const
60	<	MaxEvents = 15;
61	<
62	<	type
63	<
64	<	TEventAlert = procedure( Sender: TObject; EventName: string; EventCount: longint;
65	<	var CancelAlerts: Boolean) of object;
66	<
67	<	{ TIBEvents }
68	<
69	<	TIBEvents = class(TComponent)
70	<	private
71	<	FIBLoaded: Boolean;
72	<	FBase: TIBBase;
73	<	FEvents: TStrings;
74	<	FOnEventAlert: TEventAlert;
75	<	FEventHandler: TObject;
76	<	FRegistered: boolean;
77	<	FDeferredRegister: boolean;
78	<	procedure EventChange(sender: TObject);
79	<	function GetDatabase: TIBDatabase;
80	<	function GetDatabaseHandle: TISC_DB_HANDLE;
81	<	procedure SetDatabase( value: TIBDatabase);
82	<	procedure ValidateDatabase( Database: TIBDatabase);
83	<	procedure DoBeforeDatabaseDisconnect(Sender: TObject);
84	<	procedure DoAfterDatabaseConnect(Sender: TObject);
85	<	protected
86	<	procedure Notification( AComponent: TComponent; Operation: TOperation); override;
87	<	procedure SetEvents( value: TStrings);
88	<	procedure SetRegistered( value: boolean);
89	<
90	<	public
91	<	constructor Create( AOwner: TComponent); override;
92	<	destructor Destroy; override;
93	<	procedure RegisterEvents;
94	<	procedure UnRegisterEvents;
95	<	property DatabaseHandle: TISC_DB_HANDLE read GetDatabaseHandle;
96	<	property DeferredRegister: boolean read FDeferredRegister write FDeferredRegister;
97	<	published
98	<	property Database: TIBDatabase read GetDatabase write SetDatabase;
99	<	property Events: TStrings read FEvents write SetEvents;
100	<	property Registered: Boolean read FRegistered write SetRegistered;
101	<	property OnEventAlert: TEventAlert read FOnEventAlert write FOnEventAlert;
102	<	end;
103	<
104	<
105	<	implementation
106	<
107	<	uses
108	<	IBIntf, syncobjs, SysUtils;
109	<
110	<	type
111	<
112	<	TEventHandlerStates = (
113	<	stIdle,           {Events not monitored}
114	<	stHasEvb,         {Event Block Allocated but not queued}
115	<	stQueued,         {Waiting for Event}
116	<	stSignalled       {Event Callback signalled Event}
117	<	);
118	<
119	<	{ TEventHandler }
120	<
121	<	TEventHandler = class(TThread)
122	<	private
123	<	FOwner: TIBEvents;
124	<	FCriticalSection: TCriticalSection;   {protects race conditions in stQueued state}
125	<	{$IFDEF WINDOWS}
126	<	{Make direct use of Windows API as TEventObject don't seem to work under
127	<	Windows!}
128	<	FEventHandler: THandle;
129	<	{$ELSE}
130	<	FEventWaiting: TEventObject;
131	<	{$ENDIF}
132	<	FState: TEventHandlerStates;
133	<	FEventBuffer: PChar;
134	<	FEventBufferLen: integer;
135	<	FEventID: ISC_LONG;
136	<	FRegisteredState: Boolean;
137	<	FResultBuffer: PChar;
138	<	FEvents: TStringList;
139	<	FSignalFired: boolean;
140	<	procedure QueueEvents;
141	<	procedure CancelEvents;
142	<	procedure HandleEventSignalled(length: short; updated: PChar);
143	<	procedure DoEventSignalled;
144	<	protected
145	<	procedure Execute; override;
146	<	public
147	<	constructor Create(Owner: TIBEvents);
148	<	destructor Destroy; override;
149	<	procedure Terminate;
150	<	procedure RegisterEvents(Events: TStrings);
151	<	procedure UnregisterEvents;
152	<	end;
153	<
154	<	{This procedure is used for the event call back - note the cdecl }
155	<
156	<	procedure IBEventCallback( ptr: pointer; length: short; updated: PChar); cdecl;
157	<	begin
158	<	if (ptr = nil) or (length = 0) or (updated = nil) then
159	<	Exit;
160	<	{ Handle events asynchronously in second thread }
161	<	TEventHandler(ptr).HandleEventSignalled(length,updated);
162	<	end;
163	<
164	<
165	<
166	<	{ TEventHandler }
167	<
168	<	procedure TEventHandler.QueueEvents;
169	<	var
170	<	callback: pointer;
171	<	DBH: TISC_DB_HANDLE;
172	<	begin
173	<	if FState <> stHasEvb then
174	<	Exit;
175	<	FCriticalSection.Enter;
176	<	try
177	<	callback := @IBEventCallback;
178	<	DBH := FOwner.DatabaseHandle;
179	<	if (isc_que_events( StatusVector, @DBH, @FEventID, FEventBufferLen,
180	<	FEventBuffer, TISC_CALLBACK(callback), PVoid(Self)) <> 0) then
181	<	IBDatabaseError;
182	<	FState := stQueued
183	<	finally
184	<	FCriticalSection.Leave
185	<	end;
186	<	end;
187	<
188	<	procedure TEventHandler.CancelEvents;
189	<	var
190	<	DBH: TISC_DB_HANDLE;
191	<	begin
192	<	if FState in [stQueued,stSignalled] then
193	<	begin
194	<	FCriticalSection.Enter;
195	<	try
196	<	DBH := FOwner.DatabaseHandle;
197	<	if (isc_Cancel_events( StatusVector, @DBH, @FEventID) <> 0) then
198	<	IBDatabaseError;
199	<	FState := stHasEvb;
200	<	finally
201	<	FCriticalSection.Leave
202	<	end;
203	<	end;
204	<
205	<	if FState = stHasEvb then
206	<	begin
207	<	isc_free( FEventBuffer);
208	<	FEventBuffer := nil;
209	<	isc_free( FResultBuffer);
210	<	FResultBuffer := nil;
211	<	FState := stIdle
212	<	end;
213	<	FSignalFired := false
214	<	end;
215	<
216	<	procedure TEventHandler.HandleEventSignalled(length: short; updated: PChar);
217	<	begin
218	<	FCriticalSection.Enter;
219	<	try
220	<	if FState <> stQueued then
221	<	Exit;
222	<	Move(Updated[0], FResultBuffer[0], Length);
223	<	FState := stSignalled;
224	<	{$IFDEF WINDOWS}
225	<	SetEVent(FEventHandler);
226	<	{$ELSE}
227	<	FEventWaiting.SetEvent;
228	<	{$ENDIF}
229	<	finally
230	<	FCriticalSection.Leave
231	<	end;
232	<	end;
233	<
234	<	procedure TEventHandler.DoEventSignalled;
235	<	var
236	<	i: integer;
237	<	CancelAlerts: boolean;
238	<	Status: array[0..19] of ISC_LONG; {Note in 64 implementation the ibase.h implementation
239	<	is different from Interbase 6.0 API documentatoin}
240	<	begin
241	<	if FState <> stSignalled then
242	<	Exit;
243	<	isc_event_counts( @Status, FEventBufferLen, FEventBuffer, FResultBuffer);
244	<	CancelAlerts := false;
245	<	if not FSignalFired then
246	<	FSignalFired := true   {Ignore first time}
247	<	else
248	<	if assigned(FOwner.FOnEventAlert)  then
249	<	begin
250	<	for i := 0 to FEvents.Count - 1 do
251	<	begin
252	<	try
253	<	if (Status[i] <> 0) and not CancelAlerts then
254	<	FOwner.FOnEventAlert( self, FEvents[i], Status[i], CancelAlerts);
255	<	except
256	<	FOwner.FBase.HandleException(Self)
257	<	end;
258	<	end;
259	<	end;
260	<	FState := stHasEvb;
261	<	if  CancelAlerts then
262	<	CancelEvents
263	<	else
264	<	QueueEvents
265	<	end;
266	<
267	<	procedure TEventHandler.Execute;
268	<	begin
269	<	while not Terminated do
270	<	begin
271	<	{$IFDEF WINDOWS}
272	<	WaitForSingleObject(FEventHandler,INFINITE);
273	<	{$ELSE}
274	<	FEventWaiting.WaitFor(INFINITE);
275	<	{$ENDIF}
276	<
277	<	if not Terminated and (FState = stSignalled) then
278	<	Synchronize(DoEventSignalled)
279	<	end;
280	<	end;
281	<
282	<
283	<
284	<	constructor TEventHandler.Create(Owner: TIBEvents);
285	<	var
286	<	PSa : PSecurityAttributes;
287	<	{$IFDEF WINDOWS}
288	<	Sd : TSecurityDescriptor;
289	<	Sa : TSecurityAttributes;
290	<	begin
291	<	InitializeSecurityDescriptor(@Sd,SECURITY_DESCRIPTOR_REVISION);
292	<	SetSecurityDescriptorDacl(@Sd,true,nil,false);
293	<	Sa.nLength := SizeOf(Sa);
294	<	Sa.lpSecurityDescriptor := @Sd;
295	<	Sa.bInheritHandle := true;
296	<	PSa := @Sa;
297	<	{$ELSE}
298	<	begin
299	<	PSa:= nil;
300	<	{$ENDIF}
301	<	inherited Create(true);
302	<	FOwner := Owner;
303	<	FState := stIdle;
304	<	FCriticalSection := TCriticalSection.Create;
305	<	{$IFDEF WINDOWS}
306	<	FEventHandler := CreateEvent(PSa,false,true,nil);
307	<	{$ELSE}
308	<	FEventWaiting := TEventObject.Create(PSa,false,true,FOwner.Name+'.Events');
309	<	{$ENDIF}
310	<	FEvents := TStringList.Create;
311	<	FreeOnTerminate := true;
312	<	Resume
313	<	end;
314	<
315	<	destructor TEventHandler.Destroy;
316	<	begin
317	<	if assigned(FCriticalSection) then FCriticalSection.Free;
318	<	{$IFDEF WINDOWS}
319	<	CloseHandle(FEventHandler);
320	<	{$ELSE}
321	<	if assigned(FEventWaiting) then FEventWaiting.Free;
322	<	{$ENDIF}
323	<	if assigned(FEvents) then FEvents.Free;
324	<	inherited Destroy;
325	<	end;
326	<
327	<	procedure TEventHandler.Terminate;
328	<	begin
329	<	inherited Terminate;
330	<	{$IFDEF WINDOWS}
331	<	SetEvent(FEventHandler);
332	<	{$ELSE}
333	<	FEventWaiting.SetEvent;
334	<	{$ENDIF}
335	<	CancelEvents;
336	<	end;
337	<
338	<	procedure TEventHandler.RegisterEvents(Events: TStrings);
339	<	var
340	<	i: integer;
341	<	EventNames: array of PChar;
342	<	begin
343	<	UnregisterEvents;
344	<
345	<	if Events.Count = 0 then
346	<	exit;
347	<
348	<	setlength(EventNames,MaxEvents);
349	<	try
350	<	for i := 0 to Events.Count-1 do
351	<	EventNames[i] := PChar(Events[i]);
352	<	FEvents.Assign(Events);
353	<	FEventBufferlen := isc_event_block(@FEventBuffer,@FResultBuffer,
354	<	Events.Count,
355	<	EventNames[0],EventNames[1],EventNames[2],
356	<	EventNames[3],EventNames[4],EventNames[5],
357	<	EventNames[6],EventNames[7],EventNames[8],
358	<	EventNames[9],EventNames[10],EventNames[11],
359	<	EventNames[12],EventNames[13],EventNames[14]
360	<	);
361	<	FState := stHasEvb;
362	<	FRegisteredState := true;
363	<	QueueEvents
364	<	finally
365	<	SetLength(EventNames,0)
366	<	end;
367	<	end;
368	<
369	<	procedure TEventHandler.UnregisterEvents;
370	<	begin
371	<	if FRegisteredState then
372	<	begin
373	<	CancelEvents;
374	<	FRegisteredState := false;
375	<	end;
376	<	end;
377	<
378	<	{ TIBEvents }
379	<
380	<	procedure TIBEvents.ValidateDatabase( Database: TIBDatabase);
381	<	begin
382	<	if not assigned( Database) then
383	<	IBError(ibxeDatabaseNameMissing, [nil]);
384	<	if not Database.Connected then
385	<	IBError(ibxeDatabaseClosed, [nil]);
386	<	end;
387	<
388	<	constructor TIBEvents.Create( AOwner: TComponent);
389	<	begin
390	<	inherited Create( AOwner);
391	<	FIBLoaded := False;
392	<	CheckIBLoaded;
393	<	FIBLoaded := True;
394	<	FBase := TIBBase.Create(Self);
395	<	FBase.BeforeDatabaseDisconnect := DoBeforeDatabaseDisconnect;
396	<	FBase.AfterDatabaseConnect := DoAfterDatabaseConnect;
397	<	FEvents := TStringList.Create;
398	<	with TStringList( FEvents) do
399	<	begin
400	<	OnChange := EventChange;
401	<	Duplicates := dupIgnore;
402	<	end;
403	<	FEventHandler := TEventHandler.Create(self)
404	<	end;
405	<
406	<	destructor TIBEvents.Destroy;
407	<	begin
408	<	if FIBLoaded then
409	<	begin
410	<	UnregisterEvents;
411	<	SetDatabase(nil);
412	<	TStringList(FEvents).OnChange := nil;
413	<	FBase.Free;
414	<	FEvents.Free;
415	<	end;
416	<	if assigned(FEventHandler) then
417	<	TEventHandler(FEventHandler).Terminate;
418	<	FEventHandler := nil;
419	<	inherited Destroy;
420	<	end;
421	<
422	<
423	<
424	<	procedure TIBEvents.EventChange( sender: TObject);
425	<	begin
426	<	{ check for blank event }
427	<	if TStringList(Events).IndexOf( '') <> -1 then
428	<	IBError(ibxeInvalidEvent, [nil]);
429	<	{ 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.
1	>	{************************************************************************}
2	>	{                                                                        }
3	>	{       Borland Delphi Visual Component Library                          }
4	>	{       InterBase Express core components                                }
5	>	{                                                                        }
6	>	{       Copyright (c) 1998-2000 Inprise Corporation                      }
7	>	{                                                                        }
8	>	{    InterBase Express is based in part on the product                   }
9	>	{    Free IB Components, written by Gregory H. Deatz for                 }
10	>	{    Hoagland, Longo, Moran, Dunst & Doukas Company.                     }
11	>	{    Free IB Components is used under license.                           }
12	>	{                                                                        }
13	>	{    The contents of this file are subject to the InterBase              }
14	>	{    Public License Version 1.0 (the "License"); you may not             }
15	>	{    use this file except in compliance with the License. You            }
16	>	{    may obtain a copy of the License at http://www.Inprise.com/IPL.html }
17	>	{    Software distributed under the License is distributed on            }
18	>	{    an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either              }
19	>	{    express or implied. See the License for the specific language       }
20	>	{    governing rights and limitations under the License.                 }
21	>	{    The Original Code was created by InterBase Software Corporation     }
22	>	{       and its successors.                                              }
23	>	{    Portions created by Inprise Corporation are Copyright (C) Inprise   }
24	>	{       Corporation. All Rights Reserved.                                }
25	>	{    Contributor(s): Jeff Overcash                                       }
26	>	{                                                                        }
27	>	{    IBX For Lazarus (Firebird Express)                                  }
28	>	{    Contributor: Tony Whyman, MWA Software http://www.mwasoftware.co.uk }
29	>	{    Portions created by MWA Software are copyright McCallum Whyman      }
30	>	{    Associates Ltd 2011                                                 }
31	>	{                                                                        }
32	>	{************************************************************************}
33	>
34	>	{
35	>	This unit has been almost completely re-written as the original code was
36	>	not that robust - and I am not even sure if it worked. The IBPP C++ implementation
37	>	was used for guidance and inspiration. A permanent thread is used to receive
38	>	events from the asynchronous event handler. This then uses "Synchronize" to
39	>	process the event in the main thread.
40	>
41	>	Note that an error will occur if the TIBEvent's Registered property is set to
42	>	true before the Database has been opened.
43	>	}
44	>
45	>	unit IBEvents;
46	>
47	>	{$mode objfpc}{$H+}
48	>
49	>	interface
50	>
51	>	uses
52	>	{$IFDEF WINDOWS }
53	>	Windows,
54	>	{$ELSE}
55	>	unix,
56	>	{$ENDIF}
57	>	Classes, IBExternals, IB, IBDatabase;
58	>
59	>	const
60	>	MaxEvents = 15;
61	>
62	>	type
63	>
64	>	TEventAlert = procedure( Sender: TObject; EventName: string; EventCount: longint;
65	>	var CancelAlerts: Boolean) of object;
66	>
67	>	{ TIBEvents }
68	>
69	>	TIBEvents = class(TComponent)
70	>	private
71	>	FBase: TIBBase;
72	>	FEventIntf: IEvents;
73	>	FEvents: TStrings;
74	>	FOnEventAlert: TEventAlert;
75	>	FRegistered: boolean;
76	>	FDeferredRegister: boolean;
77	>	procedure EventHandler(Sender: IEvents);
78	>	procedure ProcessEvents;
79	>	procedure EventChange(sender: TObject);
80	>	function GetDatabase: TIBDatabase;
81	>	procedure SetDatabase( value: TIBDatabase);
82	>	procedure ValidateDatabase( Database: TIBDatabase);
83	>	procedure DoBeforeDatabaseDisconnect(Sender: TObject);
84	>	procedure DoAfterDatabaseConnect(Sender: TObject);
85	>	protected
86	>	procedure Notification( AComponent: TComponent; Operation: TOperation); override;
87	>	procedure SetEvents( value: TStrings);
88	>	procedure SetRegistered( value: boolean);
89	>
90	>	public
91	>	constructor Create( AOwner: TComponent); override;
92	>	destructor Destroy; override;
93	>	procedure RegisterEvents;
94	>	procedure UnRegisterEvents;
95	>	property DeferredRegister: boolean read FDeferredRegister write FDeferredRegister;
96	>	property EventIntf: IEvents read FEventIntf;
97	>	published
98	>	property Database: TIBDatabase read GetDatabase write SetDatabase;
99	>	property Events: TStrings read FEvents write SetEvents;
100	>	property Registered: Boolean read FRegistered write SetRegistered;
101	>	property OnEventAlert: TEventAlert read FOnEventAlert write FOnEventAlert;
102	>	end;
103	>
104	>
105	>	implementation
106	>
107	>	uses SysUtils, FBMessages;
108	>
109	>	{ TIBEvents }
110	>
111	>	procedure TIBEvents.ValidateDatabase( Database: TIBDatabase);
112	>	begin
113	>	if not assigned( Database) then
114	>	IBError(ibxeDatabaseNameMissing, [nil]);
115	>	if not Database.Connected then
116	>	IBError(ibxeDatabaseClosed, [nil]);
117	>	end;
118	>
119	>	constructor TIBEvents.Create( AOwner: TComponent);
120	>	begin
121	>	inherited Create( AOwner);
122	>	FBase := TIBBase.Create(Self);
123	>	FBase.BeforeDatabaseDisconnect := @DoBeforeDatabaseDisconnect;
124	>	FBase.AfterDatabaseConnect := @DoAfterDatabaseConnect;
125	>	FEvents := TStringList.Create;
126	>	with TStringList( FEvents) do
127	>	begin
128	>	OnChange := @EventChange;
129	>	Duplicates := dupIgnore;
130	>	end;
131	>	end;
132	>
133	>	destructor TIBEvents.Destroy;
134	>	begin
135	>	UnregisterEvents;
136	>	SetDatabase(nil);
137	>	TStringList(FEvents).OnChange := nil;
138	>	FBase.Free;
139	>	FEvents.Free;
140	>	end;
141	>
142	>	procedure TIBEvents.EventHandler(Sender: IEvents);
143	>	begin
144	>	TThread.Synchronize(nil,@ProcessEvents);
145	>	end;
146	>
147	>	procedure TIBEvents.ProcessEvents;
148	>	var EventCounts: TEventCounts;
149	>	CancelAlerts: Boolean;
150	>	i: integer;
151	>	begin
152	>	if (csDestroying in ComponentState) or (FEventIntf = nil) then Exit;
153	>	EventCounts := FEventIntf.ExtractEventCounts;
154	>	if assigned(FOnEventAlert) then
155	>	begin
156	>	CancelAlerts := false;
157	>	for i := 0 to Length(EventCounts) -1 do
158	>	begin
159	>	OnEventAlert(self,EventCounts[i].EventName,EventCounts[i].Count,CancelAlerts);
160	>	if CancelAlerts then break;
161	>	end;
162	>	end;
163	>	if CancelAlerts then
164	>	UnRegisterEvents
165	>	else
166	>	FEventIntf.AsyncWaitForEvent(@EventHandler);
167	>	end;
168	>
169	>	procedure TIBEvents.EventChange( sender: TObject);
170	>	begin
171	>	{ check for blank event }
172	>	if TStringList(Events).IndexOf( '') <> -1 then
173	>	IBError(ibxeInvalidEvent, [nil]);
174	>	{ check for too many events }
175	>	if Events.Count > MaxEvents then
176	>	begin
177	>	TStringList(Events).OnChange := nil;
178	>	Events.Delete( MaxEvents);
179	>	TStringList(Events).OnChange := @EventChange;
180	>	IBError(ibxeMaximumEvents, [nil]);
181	>	end;
182	>	if Registered  and (FEventIntf <> nil) then
183	>	begin
184	>	FEventIntf.SetEvents(Events);
185	>	FEventIntf.AsyncWaitForEvent(@EventHandler);
186	>	end;
187	>	end;
188	>
189	>	procedure TIBEvents.Notification( AComponent: TComponent;
190	>	Operation: TOperation);
191	>	begin
192	>	inherited Notification( AComponent, Operation);
193	>	if (Operation = opRemove) and (AComponent = FBase.Database) then
194	>	begin
195	>	UnregisterEvents;
196	>	FBase.Database := nil;
197	>	end;
198	>	end;
199	>
200	>	procedure TIBEvents.RegisterEvents;
201	>	begin
202	>	if FRegistered then Exit;
203	>	ValidateDatabase( Database);
204	>	if csDesigning in ComponentState then FRegistered := true
205	>	else
206	>	begin
207	>	if not FBase.Database.Connected then
208	>	FDeferredRegister := true
209	>	else
210	>	begin
211	>	FEventIntf := Database.Attachment.GetEventHandler(Events);
212	>	FEventIntf.AsyncWaitForEvent(@EventHandler);
213	>	FRegistered := true;
214	>	end;
215	>	end;
216	>	end;
217	>
218	>	procedure TIBEvents.SetEvents( value: TStrings);
219	>	begin
220	>	FEvents.Assign( value);
221	>	end;
222	>
223	>	procedure TIBEvents.SetDatabase( value: TIBDatabase);
224	>	begin
225	>	if value <> FBase.Database then
226	>	begin
227	>	if Registered then UnregisterEvents;
228	>	if assigned( value) and value.Connected then ValidateDatabase( value);
229	>	FBase.Database := value;
230	>	if (FBase.Database <> nil) and FBase.Database.Connected then
231	>	DoAfterDatabaseConnect(FBase.Database)
232	>	end;
233	>	end;
234	>
235	>	function TIBEvents.GetDatabase: TIBDatabase;
236	>	begin
237	>	Result := FBase.Database
238	>	end;
239	>
240	>	procedure TIBEvents.SetRegistered(value: boolean);
241	>	begin
242	>	FDeferredRegister := false;
243	>	if not assigned(FBase) or (FBase.Database = nil) then
244	>	begin
245	>	FDeferredRegister := value;
246	>	Exit;
247	>	end;
248	>
249	>	if value then RegisterEvents else UnregisterEvents;
250	>	end;
251	>
252	>	procedure TIBEvents.UnRegisterEvents;
253	>	begin
254	>	FDeferredRegister := false;
255	>	if not FRegistered then
256	>	Exit;
257	>	if csDesigning in ComponentState then
258	>	FRegistered := false
259	>	else
260	>	begin
261	>	FEventIntf := nil;
262	>	FRegistered := false;
263	>	end;
264	>	end;
265	>
266	>	procedure TIBEvents.DoBeforeDatabaseDisconnect(Sender: TObject);
267	>	begin
268	>	UnregisterEvents;
269	>	end;
270	>
271	>	procedure TIBEvents.DoAfterDatabaseConnect(Sender: TObject);
272	>	begin
273	>	if FDeferredRegister then
274	>	Registered := true
275	>	end;
276	>
277	>
278	>	end.

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