Detect disk activity in Delphi

Question

I'm using Delphi 2007.

I am copying files to a remote drive. When the copying ends, I shutdown/standby the machine. It can happen that some files don't get copied from buffer to disk, and the remote disk gets disconnected, so the backup is not completed. I need to detect disk activity on that disk to properly be able to take the close action on the machine.

Is there a way to detect disk activity in this scenario?

Answer 1

(Please move the additional information from the comment to your question.) AFAIK there is no Windows API to tell whether all data has been written to disk.

What you are looking for is the Windows equivalent of the Unix sync command. You could run this tool from your program. Please read the information on the linked page, this requires administrative rights, and even so it may not be enough to be sure - some disk drives have a firmware that tells the OS that all writes have completed, when in fact they have not, and unwritten data is still in the on-disk-cache. You should better add a delay after your copy action has finished, to be on the safe side.

Answer 2

I don't remember where this came from, but it works. Unfortunately I don't know how to attach stuff here, so I cannot add the dcr with an icon.

Update: Found it on torry.net, along with plenty of other components that do the same trick: http://www.torry.net/pages.php?id=252

---

// ==================== DISC DRIVE MONITOR =====================================
//
// Class and Component to encapsulate the FindXXXXChangeNotification API calls
//
// The FindXXXXChangeNotification API calls set up a disc contents change
// notification handle.  You can set a filter to control which change types
// are notified, the directory which is monitored and set whether subdirectories
// from the monitored directory are monitored as well.
//
//------------------------------------------------------------------------------
// This file contains a class derived from TThread which undertakes the disc
// monitoring and a simple component which encapsulates the thread to make
// a non-visual VCL component.  This component works at design time, monitoring
// and notifying changes live if required.
//
// Version 1.00 - Grahame Marsh 14 January 1997
// Version 1.01 - Grahame Marsh 30 December 1997
//      Bug fix - really a Win 95 bug but only surfaces in D3, not D2
//              - see notes in execute method
// Version 1.02 - Grahame Marsh 30 January 1998
//              - adapted to work with version 2.30 TBrowseDirectoryDlg
//
// Freeware - you get it for free, I take nothing, I make no promises!
//
// Please feel free to contact me: [e-mail]

unit DiscMon;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls,
  Forms, Dialogs, ShlObj;//, BrowseDr, DsgnIntf;

//=== DISC MONITORING THREAD ===================================================
// This thread will monitor a given directory and subdirectories (if required)
// for defined filtered changes.  When a change occurs the OnChange event will
// be fired, if an invalid condition is found (eg non-existent path) then
// the OnInvalid event is fired. Each event is called via the Sychronize method
// and so are VCL thread safe.
//
// The thread is created suspended, so after setting the required properties
// you must call the Resume method.

type
  TDiscMonitorThread = class(TThread)
  private
    FOnChange : TNotifyEvent;
    FOnInvalid : TNotifyEvent;
    FDirectory : string;
    FFilters : integer;
    FDestroyEvent,
    FChangeEvent : THandle;
    FMultipleChanges : boolean;
    FSubTree : boolean;
    procedure InformChange;
    procedure InformInvalid;
    procedure SetDirectory (const Value : string);
    procedure SetFilters (Value : integer);
    procedure SetMultipleChanges (Value : boolean);
    procedure SetSubTree (Value : boolean);
  protected
    procedure Execute; override;
    procedure Update;
  public
    constructor Create;
    destructor Destroy; override;
// The directory to monitor
    property Directory : string read FDirectory write SetDirectory;
// Filter condition, may be any of the FILE_NOTIFY_CHANGE_XXXXXXX constants
// ORed together.  Zero is invalid.
    property Filters : integer read FFilters write SetFilters;
// Event called when change noted in directory
    property OnChange : TNotifyEvent read FOnChange write FOnChange;
// Event called for invalid parameters
    property OnInvalid : TNotifyEvent read FOnInvalid write FOnInvalid;
// Flag multiple times per change, for instance if the Size of a file changes
// then the Time willl change as well; MultipleChanges=true will fire two events
    property MultipleChanges : boolean read FMultipleChanges write SetMultipleChanges;
// Include subdirectories below specified directory.
    property SubTree : boolean read FSubTree write SetSubTree;
  end;

//===================== DISC MONITORING COMPONENT ==============================

// specify directory string as type string so we can have our own property editor
  TDiscMonitorDirStr = type string;

// enumerated type for filter conditions (not directly usable in thread class)
// see the SetFilters procedure for the translation of these filter conditions
// into FILE_NOTIFY_CHANGE_XXXXXX constants.
  TMonitorFilter = (moFilename, moDirName, moAttributes, moSize,
                    moLastWrite, moSecurity);
// set of filter conditions
  TMonitorFilters = set of TMonitorFilter;

  TDiscMonitor = class(TComponent)
  private
    FActive : boolean;
    FMonitor : TDiscMonitorThread;
    FFilters : TMonitorFilters;
    FOnChange : TNotifyEvent;
    FOnInvalid : TNotifyEvent;
    FShowMsg : boolean;
    function GetDirectory : TDiscMonitorDirStr;
    function GetMultipleChanges : boolean;
    function GetSubTree : boolean;
    procedure SetActive (Value : boolean);
    procedure SetDirectory (Value : TDiscMonitorDirStr);
    procedure SetFilters (Value : TMonitorFilters);
    procedure SetMultipleChanges (Value : boolean);
    procedure SetSubTree (Value : boolean);
  protected
    procedure Change (Sender : TObject);
    procedure Invalid (Sender : TObject);
  public
    constructor Create (AOwner : TComponent); override;
    destructor Destroy; override;
// stop the monitoring thread running
    procedure Close;
// start the monitoring thread running
    procedure Open;
// read-only property to access the thread directly
    property Thread : TDiscMonitorThread read FMonitor;
  published
// the directory to monitor
    property Directory : TDiscMonitorDirStr read GetDirectory write SetDirectory;
// control the appearance of information messages at design time (only)
    property ShowDesignMsg : boolean read FShowMsg write FShowMsg default false;
// event called when a change is notified
    property OnChange : TNotifyEvent read FOnChange write FOnChange;
// event called if an invalid condition is found
    property OnInvalid : TNotifyEvent read FOnInvalid write FOnInvalid;
// notification filter conditions
    property Filters : TMonitorFilters read FFilters write SetFilters default [moFilename];
// Flag multiple times per change, for instance if the Size of a file changes
// then the Time willl change as well; MultipleChanges=true will fire two events
    property MultipleChanges : boolean read GetMultipleChanges write SetMultipleChanges;
// include subdirectories below the specified directory
    property SubTree : boolean read GetSubTree write SetSubTree default true;
// specify if the monitoring thread is active
    property Active : boolean read FActive write SetActive default false;
  end;

procedure Register;

implementation

//=== MONITOR THREAD ===========================================================

// Create the thread suspended.  Create two events, each are created using
// standard security, in the non-signalled state, with auto-reset and without
// names.  The FDestroyEvent will be used to signal the thread that it is to close
// down.  The FChangeEvent will be used to signal the thread when the monitoring
// conditions (directory, filters or sub-directory search) have changed.
// OnTerminate is left as false, so the user must Free the thread.

constructor TDiscMonitorThread.Create;
begin
  inherited Create (true);
  FDestroyEvent := CreateEvent (nil, false, false, nil);
  FChangeEvent := CreateEvent (nil, false, false, nil)
end;

// close OnXXXXX links, signal the thread that it is to close down
destructor TDiscMonitorThread.Destroy;
begin
  FOnChange := nil;
  FOnInvalid := nil;
  SetEvent (FDestroyEvent);
  FDirectory := '';
  inherited Destroy
end;

// called by the Execute procedure via Synchronize.  So this is VCL thread safe
procedure TDiscMonitorThread.InformChange;
begin
  if Assigned(FOnChange) then
    FOnChange(Self)
end;

// called by the Execute procedure via Synchronize.  So this is VCL thread safe
procedure TDiscMonitorThread.InformInvalid;
begin
  if Assigned (FOnInvalid) then
    FOnInvalid (Self)
end;

// Change the current directory
procedure TDiscMonitorThread.SetDirectory (const Value : string);
begin
  if Value <> FDirectory then
  begin
    FDirectory := Value;
    Update
  end
end;

// Change the current filters
procedure TDiscMonitorThread.SetFilters (Value : integer);
begin
  if Value <> FFilters then
  begin
    FFilters := Value;
    Update
  end
end;

// Change the current MultipleChanges condition
procedure TDiscMonitorThread.SetMultipleChanges (Value : boolean);
begin
  if Value <> FMultipleChanges then
    FMultipleChanges := Value;
end;

// Change the current sub-tree condition
procedure TDiscMonitorThread.SetSubTree (Value : boolean);
begin
  if Value <> FSubTree then
  begin
    FSubtree := Value;
    Update
  end
end;

// On any of the above three changes, if the thread is running then
// signal it that a change has occurred.
procedure TDiscMonitorThread.Update;
begin
  if not Suspended then
    SetEvent (FChangeEvent)
end;

// The EXECUTE procedure
//     -------
// Execute needs to:
// 1. Call FindFirstChangeNotification and use the Handle in a WaitFor...
//    to wait until the thread become signalled that a notification has occurred.
//    The OnChange event is called and then the FindNextChangeNotification is
//    the called and Execute loops back to the WaitFor
// 2. If an invalid handle is obtained from the above call, the the OnInvalid
//    event is called and then Execute waits until valid conditions are set.
// 3. If a ChangeEvent is signalled then FindCloseChangeNotification is called,
//    followed by a new FindFirstChangeNotification to use the altered
//    conditions.
// 4. If a DestroyEvent is signalled then FindCloseChangeNotification is
//    called and the two events are closed and the thread terminates.
//
// In practice WaitForMultipleObjects is used to wait for any of the conditions
// to be signalled, and the returned value used to determine which event occurred.

procedure TDiscMonitorThread.Execute;
// There appears to be a bug in win 95 where the bWatchSubTree parameter
// of FindFirstChangeNotification which is a BOOL only accepts values of
// 0 and 1 as valid, rather than 0 and any non-0 value as it should.  In D2
// BOOL was defined as 0..1 so the code worked, in D3 it is 0..-1 so
// fails. The result is FindF... produces and error message.  This fix (bodge) is
// needed to produce a 0,1 bool pair, rather that 0,-1 as declared in D3
const
  R : array [false..true] of BOOL = (BOOL (0), BOOL (1));
var
  A : array [0..2] of THandle; // used to give the handles to WaitFor...
  B : boolean;                 // set to true when the thread is to terminate
begin
  B := false;
  A [0] := FDestroyEvent;      // put DestroyEvent handle in slot 0
  A [1] := FChangeEvent;       // put ChangeEvent handle in slot 1
// make the first call to the change notification system and put the returned
// handle in slot 2.
  A [2] := FindFirstChangeNotification (PChar(FDirectory),R[fSubTree],FFilters);
  repeat

// if the change notification handle is invalid then:
    if A [2] = INVALID_HANDLE_VALUE then
    begin
  // call the OnInvalid event
      Synchronize (InformInvalid);
  // wait until either DestroyEvent or the ChangeEvents are signalled
      case WaitForMultipleObjects(2,PWOHandleArray(@A),false,INFINITE)-WAIT_OBJECT_0 of
  // DestroyEvent - close down by setting B to true
        0 : B := true;
  // try new conditions and loop back to the invalid handle test
        1 : A [2] := FindFirstChangeNotification (PChar(FDirectory),
                                                  R[fSubTree],FFilters)
      end
    end else
// handle is valid so wait for any of the change notification, destroy or
// change events to be signalled
      case WaitForMultipleObjects(3,PWOHandleArray(@A),false,INFINITE)-WAIT_OBJECT_0 of
        0 : begin
  // DestroyEvent signalled so use FindClose... and close down by setting B to true
              FindCloseChangeNotification (A [2]);
              B := true
            end;
        1 : begin
  // ChangeEvent signalled so close old conditions by FindClose... and start
  // off new conditions.  Loop back to invalid test in case new conditions are
  // invalid
              FindCloseChangeNotification (A [2]);
              A [2] := FindFirstChangeNotification (PChar(FDirectory),
                                                    R[fSubTree],FFilters)
            end;
        2 : begin
  // Notification signalled, so fire the OnChange event and then FindNext..
  // loop back to re-WaitFor... the thread
              Synchronize(InformChange);
// changed to prevent multiple notifications for the same change
// old line
              if FMultipleChanges then
                FindNextChangeNotification (A [2])
              else
                begin
                  FindCloseChangeNotification (A [2]);
                  A [2] := FindFirstChangeNotification (PChar(FDirectory),
                                                        R[fSubTree],FFilters);
                end
            end;
      end
  until B;

// closing down so chuck the two events
  CloseHandle (FChangeEvent);
  CloseHandle (FDestroyEvent)
end;

//=== MONITOR COMPONENT ========================================================

// This component encapsulates the above thread.  It has properties for
// directory, sub-directory conditions, filters, whether information messages
// should be given at design time and if the thread is active.
constructor TDiscMonitor.Create (AOwner : TComponent);
begin
  inherited Create (AOwner);
  FMonitor:=TDiscMonitorThread.Create;  // create a monitor thread
  FMonitor.OnChange:=Change;            // hook into its event handlers
  FMonitor.OnInvalid:=Invalid;
  Filters:=[moFilename];                // default filters to moFilename
  MultipleChanges:=false;               // default one event per change
  SubTree:=false                        // default no sub-tree search to on
end;

destructor TDiscMonitor.Destroy;
begin
  FMonitor.Free;                          // chuck the thread
  inherited Destroy
end;

// Change notification from the thread has occurred. Call the component's event
// handler and then, if in design mode, and if desired, put up a simple
// notification message
procedure TDiscMonitor.Change;
begin
  if Assigned (FOnChange) then
    FOnChange (Self)
  else
    if (csDesigning in ComponentState) and FShowMsg then
      ShowMessage ('Change signalled')
end;

// Invalid notification from the thread has occurred. Call the component's event
// handler and then, if in design mode, and if desired, put up a simple
// notification message
procedure TDiscMonitor.Invalid;
begin
  if Assigned (FOnInvalid) then
    FOnInvalid (Self)
  else
    if (csDesigning in ComponentState) and FShowMsg then
      ShowMessage ('Invalid parameter signalled')
end;

// Stop the monitor running
procedure TDiscMonitor.Close;
begin
  Active := false
end;

// Run the monitor
procedure TDiscMonitor.Open;
begin
  Active := true
end;

// Control the thread by using it's resume and suspend methods
procedure TDiscMonitor.SetActive (Value : boolean);
begin
  if Value <> FActive then
  begin
    FActive := Value;
    if Active then
    begin
      FMonitor.Resume;
      FMonitor.Update
    end else
      FMonitor.Suspend
  end
end;

// get the current directory from the thread
function TDiscMonitor.GetDirectory : TDiscMonitorDirStr;
begin
  Result := FMonitor.Directory
end;

// get the current MultipleChanges status from the thread
function TDiscMonitor.GetMultipleChanges : boolean;
begin
  Result := FMonitor.MultipleChanges
end;

// get the current sub-tree status from the thread
function TDiscMonitor.GetSubTree : boolean;
begin
  Result := FMonitor.SubTree
end;

// set the directory to monitor
procedure TDiscMonitor.SetDirectory (Value : TDiscMonitorDirStr);
begin
  FMonitor.Directory := Value
end;

// Change the filter conditions.  The thread uses the raw windows constants
// (FILE_NOTIFY_CHANGE_XXXX) but the components uses a set of enumurated type.
// It is therefore necessary to translate from the component format into
// an integer value for the thread.
procedure TDiscMonitor.SetFilters (Value : TMonitorFilters);
const
  XlatFileNotify : array [moFilename..moSecurity] of integer =
    (FILE_NOTIFY_CHANGE_FILE_NAME,  FILE_NOTIFY_CHANGE_DIR_NAME,
     FILE_NOTIFY_CHANGE_ATTRIBUTES, FILE_NOTIFY_CHANGE_SIZE,
     FILE_NOTIFY_CHANGE_LAST_WRITE, FILE_NOTIFY_CHANGE_SECURITY);
var
  L : TMonitorFilter;
  I : integer;
begin
  if Value <> FFilters then
    if Value = [] then
      ShowMessage ('Some filter condition must be set.')
    else begin
      FFilters := Value;
      I := 0;
      for L := moFilename to moSecurity do
        if L in Value then
          I := I or XlatFileNotify [L];
      FMonitor.Filters := I;
    end
end;

// set the MultipleChanges status in the thread
procedure TDiscMonitor.SetMultipleChanges (Value : boolean);
begin
  FMonitor.MultipleChanges:=Value
end;

// set the sub-tree status in the thread
procedure TDiscMonitor.SetSubTree (Value : boolean);
begin
  FMonitor.SubTree:=Value
end;

procedure Register;
begin
  RegisterComponents ('Samples', [TDiscMonitor]);
end;

end.

---

Answer 3

It depends on the type of disk activity you want to detect.

The language "Delphi" in-and-of itself probably has no libraries to help you with this.

• Using Win32 API calls you can Obtain Directory Change Notifications.
• In .NET you can use a FileSystemWatcher to monitor directories.

If those don't do it for you then you need to drop down to hooking the operating system calls or more likely the hardware level which usually involves writing a device driver hooking the IDT (Interrupt Descriptor Table). I recommend the book Rootkits for more information.

Answer 4

Also see JvChangeNotify.TJvChangeNotify class in JCL.