aboutsummaryrefslogtreecommitdiffstats
path: root/VideoPreview/src/lib/other/DirWatch.pas
blob: 1e00ec5dc74af5c34a799095c3472ef4f879452d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
unit DirWatch;

// -----------------------------------------------------------------------------
// Component Name:  TDirectoryWatch                                            .
// Module:          DirWatch                                                   .
// Description:     Implements watching for file changes in a designated       .
//                  directory (or directories).                                .
// Version:         1.4                                                        .
// Date:            10-MAR-2003                                                .
// Target:          Win32, Delphi 3 - Delphi 7                                 .
// Author:          Angus Johnson, angusj-AT-myrealbox-DOT-com                 .
//                  A portion of code has been copied from the Drag & Drop     .
//                  Component Suite which I co-authored with Anders Melander.  .
// Copyright:       � 2003 Angus Johnson                                       .
//                                                                             .
// Usage:           1. Add a TDirectoryWatch component to your form.           .
//                  2. Set its Directory property                              .
//                  3. If you wish to watch its subdirectories too then set    .
//                  the WatchSubDir property to true                           .
//                  4. Assign the OnChange event                               .
//                  5. Set Active to true                                      .
// -----------------------------------------------------------------------------

interface

{$IFDEF FPC}
  {$MODE Delphi}
  {$H+} // use long strings
{$ENDIF}

uses
  Windows,
  Messages,
  Classes,
  {$IFDEF FPC}
  WinAllocation,
  {$ENDIF}
  SysUtils;

type
  TNotifyFilters = set of (nfFilename, nfDirname, nfAttrib,
    nfSize, nfLastWrite, nfSecurity);

  TWatchThread = class;             //forward declaration

  TDirectoryWatch = class(TComponent)
  private
    fWindowHandle: THandle;
    fWatchThread: TWatchThread;
    fWatchSubDirs: boolean;
    fDirectory: string;
    fActive: boolean;
    fNotifyFilters: TNotifyFilters; //see FindFirstChangeNotification in winAPI
    fOnChangeEvent: TNotifyEvent;
    procedure SetActive(aActive: boolean);
    procedure SetDirectory(aDir: string);
    procedure SetWatchSubDirs(aWatchSubDirs: boolean);
    procedure SetNotifyFilters(aNotifyFilters: TNotifyFilters);
    procedure WndProc(var aMsg: TMessage);
  public
    constructor Create(aOwner: TComponent); override;
    destructor Destroy; override;
  published
    property Directory: string read fDirectory write SetDirectory;
    property NotifyFilters: TNotifyFilters
      read fNotifyFilters write SetNotifyFilters;
    property WatchSubDirs: boolean read fWatchSubDirs write SetWatchSubDirs;
    property Active: boolean read fActive write SetActive;
    property OnChange: TNotifyEvent read fOnChangeEvent write fOnChangeEvent;
  end;

  TWatchThread = class(TThread)
  private
    fOwnerHdl: Thandle;
    fChangeNotify : THandle; //Signals whenever Windows detects a change in    .
                             //the watched directory                           .
    fBreakEvent: THandle;    //Signals when either the Directory property      .
                             //changes or when the thread terminates           .
    fDirectory: string;
    fWatchSubDirs: longbool;
    fNotifyFilters: dword;
    fFinished: boolean;    
  protected
    procedure SetDirectory(const Value: string);
    procedure ProcessFilenameChanges;
    procedure Execute; override;
  public
    constructor Create( OwnerHdl: THandle;
      const InitialDir: string; WatchSubDirs: boolean; NotifyFilters: dword);
    destructor Destroy; override;
    procedure Terminate;
    property Directory: string write SetDirectory;
  end;

procedure Register;

implementation

const
  NOTIFYCHANGE_MESSAGE = WM_USER + 1;

resourcestring
  sInvalidDir = 'Invalid Directory: ';

//----------------------------------------------------------------------------
// Miscellaneous functions ...
//----------------------------------------------------------------------------

procedure Register;
begin
  RegisterComponents('Samples', [TDirectoryWatch]);
end;
//----------------------------------------------------------------------------

function DirectoryExists(const Name: string): Boolean;
var
  Code: Integer;
begin
  Code := GetFileAttributes(PChar(Name));
  Result := (Code <> -1) and (FILE_ATTRIBUTE_DIRECTORY and Code <> 0);
end;

//----------------------------------------------------------------------------
// TDirectoryWatch methods ...
//----------------------------------------------------------------------------

constructor TDirectoryWatch.Create(aOwner: TComponent);
begin
  inherited Create(aOwner);
  //default Notify values - notify if either a file name or a directory name
  //changes or if a file is modified ...
  fNotifyFilters := [nfFilename, nfDirname, nfLastWrite];
  fDirectory := 'C:\';
  //this non-visual control needs to handle messages, so ...
  if not (csDesigning in ComponentState) then
    fWindowHandle := AllocateHWnd(WndProc);
end;
//----------------------------------------------------------------------------

destructor TDirectoryWatch.Destroy;
begin
  Active := false;
  if not (csDesigning in ComponentState) then
    DeallocateHWnd(fWindowHandle);
  inherited Destroy;
end;
//----------------------------------------------------------------------------

procedure TDirectoryWatch.WndProc(var aMsg: TMessage);
begin
  with aMsg do
    if Msg = NOTIFYCHANGE_MESSAGE then
    begin
      if assigned(OnChange) then OnChange(self);
    end else
      Result := DefWindowProc(FWindowHandle, Msg, wParam, lParam);
end;
//------------------------------------------------------------------------------

procedure TDirectoryWatch.SetNotifyFilters(aNotifyFilters: TNotifyFilters);
begin
  if aNotifyFilters = fNotifyFilters then exit;
  fNotifyFilters := aNotifyFilters;
  if assigned(fWatchThread) then
  begin
    Active := false;
    Active := true;
  end;
end;
//------------------------------------------------------------------------------

procedure TDirectoryWatch.SetWatchSubDirs(aWatchSubDirs: boolean);
begin
  if aWatchSubDirs = fWatchSubDirs then exit;
  fWatchSubDirs := aWatchSubDirs;
  if assigned(fWatchThread) then
  begin
    Active := false;
    Active := true;
  end;
end;
//------------------------------------------------------------------------------

procedure TDirectoryWatch.SetDirectory(aDir: string);
begin
  if aDir = '' then
  begin
    Active := false;
    fDirectory := '';
    exit;
  end;
  if (aDir[length(aDir)] <> '\') then aDir := aDir + '\';
  if aDir = fDirectory then exit;
  if not (csDesigning in ComponentState) and not DirectoryExists(aDir) then
    raise Exception.Create( sInvalidDir + aDir);
  fDirectory := aDir;
  if assigned(fWatchThread) then
    fWatchThread.Directory := fDirectory;
end;
//------------------------------------------------------------------------------

procedure TDirectoryWatch.SetActive(aActive: boolean);
var
  nf: dword;
begin
  if aActive = fActive then exit;
  fActive := aActive;
  if csDesigning in ComponentState then exit;
  if fActive then
  begin
    if not DirectoryExists(fDirectory) then
    begin
      fActive := false;
      raise Exception.Create(sInvalidDir + fDirectory);
    end;
    nf := 0;
    if nfFilename in fNotifyFilters then
      nf := nf or FILE_NOTIFY_CHANGE_FILE_NAME;
    if nfDirname in fNotifyFilters then
      nf := nf or FILE_NOTIFY_CHANGE_DIR_NAME;
    if nfAttrib in fNotifyFilters then
      nf := nf or FILE_NOTIFY_CHANGE_ATTRIBUTES;
    if nfSize in fNotifyFilters then
      nf := nf or FILE_NOTIFY_CHANGE_SIZE;
    if nfLastWrite in fNotifyFilters then
      nf := nf or FILE_NOTIFY_CHANGE_LAST_WRITE;
    if nfSecurity in fNotifyFilters then
      nf := nf or FILE_NOTIFY_CHANGE_SECURITY;
    fWatchThread := TWatchThread.Create(
      fWindowHandle, fDirectory, fWatchSubDirs, nf);
  end else
  begin
    fWatchThread.Terminate;
    fWatchThread := nil;
  end;
end;

//----------------------------------------------------------------------------
// TWatchThread methods ...
//----------------------------------------------------------------------------

constructor TWatchThread.Create(OwnerHdl: THandle;
  const InitialDir: string; WatchSubDirs: boolean; NotifyFilters: dword);
begin
  inherited Create(True);       
  fOwnerHdl := OwnerHdl;
  if WatchSubDirs then
    cardinal(fWatchSubDirs) := 1 //workaround a Win9x OS issue
  else
    fWatchSubDirs := false;
  FreeOnTerminate := true;
  Priority := tpLowest;
  fDirectory := InitialDir;
  fNotifyFilters := NotifyFilters;
  fBreakEvent := windows.CreateEvent(nil, False, False, nil);
  Resume;
end;
//------------------------------------------------------------------------------

destructor TWatchThread.Destroy;
begin
  CloseHandle(fBreakEvent);
  inherited Destroy;
end;
//------------------------------------------------------------------------------

procedure TWatchThread.SetDirectory(const Value: string);
begin
  if (Value = FDirectory) then exit;
  FDirectory := Value;
  SetEvent(fBreakEvent);
end;
//------------------------------------------------------------------------------

procedure TWatchThread.Terminate;
begin
  inherited Terminate;
  SetEvent(fBreakEvent);
  while not fFinished do sleep(10); //avoids a reported resource leak
                                    //if called while closing the application.
end;
//------------------------------------------------------------------------------

procedure TWatchThread.Execute;
begin
  //OUTER LOOP - manages Directory property reassignments
  while (not Terminated) do
  begin
    fChangeNotify := FindFirstChangeNotification(pchar(fDirectory),
      fWatchSubDirs, fNotifyFilters);
    if (fChangeNotify = INVALID_HANDLE_VALUE) then
      //Can't monitor the specified directory so we'll just wait for
      //a new Directory assignment or the thread terminating ...
      WaitForSingleObject(fBreakEvent, INFINITE)
    else
      try
        //Now do the INNER loop...
        ProcessFilenameChanges;
      finally
        FindCloseChangeNotification(fChangeNotify);
      end;
  end;
  fFinished := true;
end;
//------------------------------------------------------------------------------

procedure TWatchThread.ProcessFilenameChanges;
var
  WaitResult : DWORD;
  HandleArray : array[0..1] of THandle;
const
  TEN_MSECS = 10;
  HUNDRED_MSECS = 100;
begin
  HandleArray[0] := fBreakEvent;
  HandleArray[1] := fChangeNotify;
  //INNER LOOP - exits only when fBreakEvent signaled
  while (not Terminated) do
  begin
    //waits for either fChangeNotify or fBreakEvent ...
    WaitResult := WaitForMultipleObjects(2, @HandleArray, False, INFINITE);
    if (WaitResult = WAIT_OBJECT_0 + 1) then //fChangeNotify
    begin
      repeat //ie: if a number of files are changing in a block
             //just post the one notification message ...
        FindNextChangeNotification(fChangeNotify);
      until Terminated or
        (WaitForSingleObject(fChangeNotify, TEN_MSECS) <> WAIT_OBJECT_0);
      if Terminated then break;
      //OK, now notify the main thread (before restarting inner loop)...
      PostMessage(fOwnerHdl, NOTIFYCHANGE_MESSAGE, 0, 0);
    end else //fBreakEvent ...
    begin
      //If the Directory property is undergoing multiple rapid reassignments
      //wait 'til this stops before restarting monitoring of a new directory ...
      while (not Terminated) and
        (WaitForSingleObject(fBreakEvent, HUNDRED_MSECS) = WAIT_OBJECT_0) do;
      break; //EXIT LOOP HERE
    end;
  end;
end;
//------------------------------------------------------------------------------
//------------------------------------------------------------------------------

end.