How can i remove a USB flash disk programmatically using delphi?

Question

How can I detect and remove a USB flash disk programatically using delphi?

I have seen some of the examples in this website, but they lack clear explanation on how to go about it!

Please examples will really help!

Answer 1

This is a quick and dirty translation of this sample code to remove a drive, from support.microsoft.com. It does however work only for users with admin permissions on my system.

For more information on working with USB devices in general follow the link in this answer by concept03.

function OpenVolume(ADrive: char): THandle;
var
  RootName, VolumeName: string;
  AccessFlags: DWORD;
begin
  RootName := ADrive + ':\'; (* '\'' // keep SO syntax highlighting working *)
  case GetDriveType(PChar(RootName)) of
    DRIVE_REMOVABLE:
      AccessFlags := GENERIC_READ or GENERIC_WRITE;
    DRIVE_CDROM:
      AccessFlags := GENERIC_READ;
  else
    Result := INVALID_HANDLE_VALUE;
    exit;
  end;
  VolumeName := Format('\\.\%s:', [ADrive]);
  Result := CreateFile(PChar(VolumeName), AccessFlags,
    FILE_SHARE_READ or FILE_SHARE_WRITE, nil, OPEN_EXISTING, 0, 0);
  if Result = INVALID_HANDLE_VALUE then
    RaiseLastWin32Error;
end;

function LockVolume(AVolumeHandle: THandle): boolean;
const
  LOCK_TIMEOUT = 10 * 1000; // 10 Seconds
  LOCK_RETRIES = 20;
  LOCK_SLEEP = LOCK_TIMEOUT div LOCK_RETRIES;

// #define FSCTL_LOCK_VOLUME CTL_CODE(FILE_DEVICE_FILE_SYSTEM, 6, METHOD_BUFFERED, FILE_ANY_ACCESS)
  FSCTL_LOCK_VOLUME = (9 shl 16) or (0 shl 14) or (6 shl 2) or 0;
var
  Retries: integer;
  BytesReturned: Cardinal;
begin
  for Retries := 1 to LOCK_RETRIES do begin
    Result := DeviceIoControl(AVolumeHandle, FSCTL_LOCK_VOLUME, nil, 0,
      nil, 0, BytesReturned, nil);
    if Result then
      break;
    Sleep(LOCK_SLEEP);
  end;
end;

function DismountVolume(AVolumeHandle: THandle): boolean;
const
// #define FSCTL_DISMOUNT_VOLUME CTL_CODE(FILE_DEVICE_FILE_SYSTEM, 8, METHOD_BUFFERED, FILE_ANY_ACCESS)
  FSCTL_DISMOUNT_VOLUME = (9 shl 16) or (0 shl 14) or (8 shl 2) or 0;
var
  BytesReturned: Cardinal;
begin
  Result := DeviceIoControl(AVolumeHandle, FSCTL_DISMOUNT_VOLUME, nil, 0,
    nil, 0, BytesReturned, nil);
  if not Result then
    RaiseLastWin32Error;
end;

function PreventRemovalOfVolume(AVolumeHandle: THandle;
  APreventRemoval: boolean): boolean;
const
// #define IOCTL_STORAGE_MEDIA_REMOVAL CTL_CODE(IOCTL_STORAGE_BASE, 0x0201, METHOD_BUFFERED, FILE_READ_ACCESS)
  IOCTL_STORAGE_MEDIA_REMOVAL = ($2d shl 16) or (1 shl 14) or ($201 shl 2) or 0;
type
  TPreventMediaRemoval = record
    PreventMediaRemoval: BOOL;
  end;
var
  BytesReturned: Cardinal;
  PMRBuffer: TPreventMediaRemoval;
begin
  PMRBuffer.PreventMediaRemoval := APreventRemoval;
  Result := DeviceIoControl(AVolumeHandle, IOCTL_STORAGE_MEDIA_REMOVAL,
    @PMRBuffer, SizeOf(TPreventMediaRemoval), nil, 0, BytesReturned, nil);
  if not Result then
    RaiseLastWin32Error;
end;

function AutoEjectVolume(AVolumeHandle: THandle): boolean;
const
// #define IOCTL_STORAGE_EJECT_MEDIA CTL_CODE(IOCTL_STORAGE_BASE, 0x0202, METHOD_BUFFERED, FILE_READ_ACCESS)
  IOCTL_STORAGE_EJECT_MEDIA = ($2d shl 16) or (1 shl 14) or ($202 shl 2) or 0;
var
  BytesReturned: Cardinal;
begin
  Result := DeviceIoControl(AVolumeHandle, IOCTL_STORAGE_EJECT_MEDIA, nil, 0,
    nil, 0, BytesReturned, nil);
  if not Result then
    RaiseLastWin32Error;
end;

function EjectVolume(ADrive: char): boolean;
var
  VolumeHandle: THandle;
begin
  Result := FALSE;
  // Open the volume
  VolumeHandle := OpenVolume(ADrive);
  if VolumeHandle = INVALID_HANDLE_VALUE then
    exit;
  try
    // Lock and dismount the volume
    if LockVolume(VolumeHandle) and DismountVolume(VolumeHandle) then begin
      // Set prevent removal to false and eject the volume
      if PreventRemovalOfVolume(VolumeHandle, FALSE) then
        AutoEjectVolume(VolumeHandle);
    end;
  finally
    // Close the volume so other processes can use the drive
    CloseHandle(VolumeHandle);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  EjectVolume('E');
end;