mirror of
https://github.com/CloudDelphi/Virtual-File-System
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319 lines
10 KiB
ObjectPascal
319 lines
10 KiB
ObjectPascal
unit VfsWatching;
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(*
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Description: Provides means to watch for mapped directories changes and refresh VFS.
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Works unreliably when trying to watch the whole logical drive.
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*)
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(***) interface (***)
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uses
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Windows, SysUtils, Math,
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Utils, Concur, WinUtils, StrLib, WinNative,
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VfsBase, VfsUtils;
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(***) implementation (***)
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type
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(* Import *)
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THandle = Windows.THandle;
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const
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(* Import *)
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INVALID_HANDLE_VALUE = Windows.INVALID_HANDLE_VALUE;
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STOP_EVENT_HANDLE_IND = 0;
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NOTIFICATION_HANDLE_INDEX = 1;
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NUM_WATCHED_HANDLES = 2;
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type
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TDirChangeAction = (NOTIFY_FILE_ADDED, NOTIFY_FILE_REMOVED, NOTIFY_FILE_MODIFIED, NOTIFY_FILE_RENAMED_FROM_NAME, NOTIFY_FILE_RENAMED_TO_NAME,
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NOTIFY_STOP_EVENT, NOTIFY_TIMEOUT, NOTIFY_TOO_MANY_CHANGES, NOTIFY_UNKNOWN_ACTION);
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const
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NOTIFY_ESSENTIAL = FILE_NOTIFY_CHANGE_FILE_NAME or FILE_NOTIFY_CHANGE_DIR_NAME or FILE_NOTIFY_CHANGE_ATTRIBUTES or FILE_NOTIFY_CHANGE_SIZE or FILE_NOTIFY_CHANGE_CREATION;
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NO_STOP_EVENT = 0;
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INFINITE = Windows.INFINITE;
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type
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(* Directory change record *)
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TDirChange = record
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Action: TDirChangeAction;
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(* Absolute expanded and normalized path to file, that triggered notification *)
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FilePath: WideString;
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end;
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IDirChangesIterator = interface
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function IterNext ({out} var DirChange: TDirChange; StopEvent: THandle = 0; Timeout: integer = integer(Windows.INFINITE); NotifyFilter: cardinal = NOTIFY_ESSENTIAL): boolean;
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end;
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TDirChangesIterator = class (Utils.TManagedObject, IDirChangesIterator)
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protected const
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BUF_SIZE = 65500;
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protected
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{O} fDirHandle: THandle;
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{O} fNotifyEvent: THandle;
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fDirPath: WideString;
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fBuf: array [0..BUF_SIZE - 1] of byte;
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fBufSize: integer;
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fBufPos: integer;
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fIsEnd: boolean;
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public
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constructor Create (const DirPath: WideString); overload;
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destructor Destroy; override;
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function IterNext ({out} var DirChange: TDirChange; StopEvent: THandle = 0; Timeout: integer = integer(Windows.INFINITE); NotifyFilter: cardinal = NOTIFY_ESSENTIAL): boolean;
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end; // .class TDirChangesIterator
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var
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WatcherCritSection: Concur.TCritSection;
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AbsWatcherDir: WideString;
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WatcherDebounceInterval: integer;
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WatcherStopEvent: THandle;
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WatcherIsRunning: boolean;
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WatcherThreadHandle: THandle;
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WatcherThreadId: cardinal;
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function IsValidHandle (Handle: THandle): boolean; inline;
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begin
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result := (Handle <> 0) and (Handle <> INVALID_HANDLE_VALUE);
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end;
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constructor TDirChangesIterator.Create (const DirPath: WideString);
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const
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MANUAL_RESET_EVENT = true;
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begin
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Self.fDirPath := VfsUtils.NormalizePath(DirPath);
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Self.fDirHandle := Windows.CreateFileW(PWideChar(Self.fDirPath), Windows.GENERIC_READ, Windows.FILE_SHARE_READ or Windows.FILE_SHARE_WRITE, nil,
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Windows.OPEN_EXISTING, Windows.FILE_FLAG_BACKUP_SEMANTICS or Windows.FILE_FLAG_OVERLAPPED, 0);
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if IsValidHandle(Self.fDirHandle) then begin
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Self.fNotifyEvent := Windows.CreateEventW(nil, MANUAL_RESET_EVENT, false, nil);
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if not IsValidHandle(Self.fNotifyEvent) then begin
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Windows.CloseHandle(Self.fDirHandle);
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Self.fDirHandle := 0;
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end;
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end;
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Self.fIsEnd := not IsValidHandle(Self.fDirHandle);
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end; // .constructor TDirChangesIterator.Create
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destructor TDirChangesIterator.Destroy;
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begin
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if IsValidHandle(Self.fDirHandle) then begin
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Windows.CloseHandle(Self.fDirHandle);
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end;
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if IsValidHandle(Self.fNotifyEvent) then begin
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Windows.CloseHandle(Self.fNotifyEvent);
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end;
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end;
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function DecodeNativeDirChangeAction (Action: integer): TDirChangeAction;
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begin
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case Action of
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Windows.FILE_ACTION_ADDED: result := NOTIFY_FILE_ADDED;
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Windows.FILE_ACTION_REMOVED: result := NOTIFY_FILE_REMOVED;
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Windows.FILE_ACTION_MODIFIED: result := NOTIFY_FILE_MODIFIED;
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Windows.FILE_ACTION_RENAMED_OLD_NAME: result := NOTIFY_FILE_RENAMED_FROM_NAME;
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Windows.FILE_ACTION_RENAMED_NEW_NAME: result := NOTIFY_FILE_RENAMED_TO_NAME;
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else
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result := NOTIFY_UNKNOWN_ACTION;
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end;
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end;
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function TDirChangesIterator.IterNext ({out} var DirChange: TDirChange; StopEvent: THandle = 0; Timeout: integer = integer(Windows.INFINITE); NotifyFilter: cardinal = NOTIFY_ESSENTIAL): boolean;
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const
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WATCH_SUBTREE = true;
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WAIT_OVERLAPPED = true;
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var
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{n} NotifInfoInBuf: WinNative.PFILE_NOTIFY_INFORMATION;
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AsyncRes: Windows.TOverlapped;
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TriggeredEvent: THandle;
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Dummy: integer;
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begin
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NotifInfoInBuf := nil;
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// * * * * * //
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result := not Self.fIsEnd;
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if not result then begin
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exit;
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end;
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if Timeout = 0 then begin
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DirChange.Action := NOTIFY_TIMEOUT;
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exit;
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end;
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if Self.fBufPos < fBufSize then begin
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NotifInfoInBuf := @Self.fBuf[Self.fBufPos];
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DirChange.Action := DecodeNativeDirChangeAction(NotifInfoInBuf.Action);
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if DirChange.Action = NOTIFY_FILE_REMOVED then begin
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DirChange.FilePath := VfsUtils.AddBackslash(Self.fDirPath) + NotifInfoInBuf.GetFileName;
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DirChange.FilePath := VfsUtils.AddBackslash(WinUtils.GetLongPathW(StrLib.ExtractDirPathW(DirChange.FilePath))) + StrLib.ExtractFileNameW(DirChange.FilePath);
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end else begin
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DirChange.FilePath := WinUtils.GetLongPathW(VfsUtils.AddBackslash(Self.fDirPath) + NotifInfoInBuf.GetFileName);
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end;
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Self.fBufPos := Utils.IfThen(NotifInfoInBuf.NextEntryOffset <> 0, Self.fBufPos + integer(NotifInfoInBuf.NextEntryOffset), Self.BUF_SIZE);
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end else begin
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FillChar(AsyncRes, sizeof(AsyncRes), 0);
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AsyncRes.hEvent := Self.fNotifyEvent;
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Windows.ResetEvent(Self.fNotifyEvent);
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Self.fBufSize := 0;
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Self.fBufPos := 0;
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result := Windows.ReadDirectoryChangesW(Self.fDirHandle, @Self.fBuf, sizeof(Self.fBuf), WATCH_SUBTREE, NotifyFilter, @Dummy, @AsyncRes, nil);
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if result then begin
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DirChange.FilePath := '';
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case WinUtils.WaitForObjects([StopEvent, Self.fNotifyEvent], TriggeredEvent, Timeout) of
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WinUtils.WR_WAITED: begin
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if TriggeredEvent = StopEvent then begin
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DirChange.Action := NOTIFY_STOP_EVENT;
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end else begin
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result := Windows.GetOverlappedResult(Self.fNotifyEvent, AsyncRes, cardinal(Self.fBufSize), not WAIT_OVERLAPPED);
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if result then begin
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if Self.fBufSize = 0 then begin
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DirChange.Action := NOTIFY_TOO_MANY_CHANGES;
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end else if Self.fBufSize < sizeof(NotifInfoInBuf^) + sizeof(WideChar) then begin
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result := false;
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end else begin
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result := Self.IterNext(DirChange, StopEvent, Timeout, NotifyFilter);
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end;
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end;
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end;
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end; // .case WR_WAITED
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WinUtils.WR_TIMEOUT: begin
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DirChange.Action := NOTIFY_TIMEOUT;
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end;
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else
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result := false;
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end; // .switch wait result
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end; // .if
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Self.fIsEnd := not result;
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end; // .else
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end; // .function TDirChangesIterator.IterNext
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function ReadDirChanges (const DirPath: WideString): IDirChangesIterator;
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begin
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result := TDirChangesIterator.Create(DirPath);
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end;
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function WatcherThreadProc (Arg: integer): integer; stdcall;
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var
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IsEnd: LONGBOOL;
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NeedFullRescan: LONGBOOL;
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CurrentTime: Int64;
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LastChangeTime: Int64;
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PlannedRescanTime: Int64;
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Timeout: integer;
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DummyEvent: THandle;
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DirChangesScanner: IDirChangesIterator;
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DirChange: TDirChange;
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begin
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DirChangesScanner := nil;
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// * * * * * //
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IsEnd := false;
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NeedFullRescan := false;
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LastChangeTime := 0;
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result := 0;
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with VfsBase.GetThreadVfsDisabler do begin
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DisableVfsForThread;
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try
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while not IsEnd do begin
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CurrentTime := GetMicroTime;
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PlannedRescanTime := LastChangeTime + Int64(WatcherDebounceInterval);
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if NeedFullRescan and (PlannedRescanTime <= CurrentTime) then begin
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VfsBase.RefreshVfs;
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NeedFullRescan := false;
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end;
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if DirChangesScanner = nil then begin
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DirChangesScanner := TDirChangesIterator.Create(AbsWatcherDir);
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end;
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// Failed to start watching directory
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if not DirChangesScanner.IterNext(DirChange, WatcherStopEvent, Utils.IfThen(boolean(NeedFullRescan), integer(PlannedRescanTime - CurrentTime), integer(Windows.INFINITE))) then begin
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// Force scanner recreation later
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DirChangesScanner := nil;
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// Wait and retry, unless stop signal is received
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Timeout := Utils.IfThen(NeedFullRescan, Min(WatcherDebounceInterval, integer(PlannedRescanTime - CurrentTime)), WatcherDebounceInterval);
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if WinUtils.WaitForObjects([WatcherStopEvent], DummyEvent, Timeout) = WinUtils.WR_WAITED then begin
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IsEnd := true;
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end;
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// Ok, got some signal
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end else begin
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if DirChange.Action = NOTIFY_STOP_EVENT then begin
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IsEnd := true;
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end else if DirChange.Action = NOTIFY_TIMEOUT then begin
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// Will perform full rescan on next loop iteration
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end else if DirChange.Action in [NOTIFY_FILE_ADDED, NOTIFY_FILE_REMOVED, NOTIFY_FILE_RENAMED_FROM_NAME, NOTIFY_FILE_RENAMED_TO_NAME, NOTIFY_UNKNOWN_ACTION, NOTIFY_TOO_MANY_CHANGES] then begin
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LastChangeTime := WinUtils.GetMicroTime;
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NeedFullRescan := true;
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end else if DirChange.Action = NOTIFY_FILE_MODIFIED then begin
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if not NeedFullRescan then begin
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VfsBase.RefreshMappedFile(DirChange.FilePath);
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end;
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LastChangeTime := WinUtils.GetMicroTime;
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end;
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end; // .else
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end; // .while
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finally
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RestoreVfsForThread;
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end; // .try
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end; // .with
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end; // .function WatcherThreadProc
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function RunWatcher (const WatchDir: WideString; DebounceInterval: integer): boolean;
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const
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MANUAL_RESET = true;
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begin
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with WatcherCritSection do begin
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Enter;
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result := not WatcherIsRunning;
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if result then begin
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AbsWatcherDir := VfsUtils.NormalizePath(WatchDir);
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WatcherDebounceInterval := Max(0, DebounceInterval);
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if not WinUtils.IsValidHandle(WatcherStopEvent) then begin
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WatcherStopEvent := Windows.CreateEventW(nil, MANUAL_RESET, false, nil);
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result := WinUtils.IsValidHandle(WatcherStopEvent);
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end;
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if result then begin
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WatcherThreadHandle := Windows.CreateThread(nil, 0, @WatcherThreadProc, nil, 0, WatcherThreadId);
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end;
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end;
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Leave;
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end;
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end; // .function RunWatcher
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end. |