VB 6 and USB Flash Disks

If you are as curious as I am, you have probably wondered whether or not it is possible to determine if a memory stick was plugged in or taken out. To answer your question, yes you can! As the saying goes: Curiosity killed the cat. In this case, if you are not careful, curiosity can cause very serious errors, even some bad, unpredictable results. So, if you are careful and do things right, everything will work smoothly, so make sure to follow every step carefully, and double check your progress against mine.

I will cover how to determine whether or not a disk is plugged in or taken out in this article—that is the main topic, but another “thing” I’ve been wondering about was: How can you make the disk Autorun, similar to CD drives, and, how can you run a normal VB 6 program from this disk, without the need of installing it on the client machine? Sound interesting? Well, it’s time to get started.

What Is Needed?

The obvious answer would be: A Lot Of APIs. Now, for the inexperienced VB 6 developer, the Win 32 Application Programming Interface would seem too advanced or too complicated to go into. To put you a bit more at ease, I won’t be shy in mentioning the fact that many a experienced VB 6 developer finds the API just as scary as you! You may think that if experienced developers find APIs scary, they must indeed be extremely difficult. No; with time you will realise that the Win 32 API is extremely huge—there are literally millions of pages written on the various APIs found—and still some of the APIs remain a mystery. In case you haven’t run away in fear for the APIs, you could have a look at these resources about the API.

The Needed APIs

In the sample program, you will be using the following APIs:

API Name API Description/Use
SetWindowLong The SetWindowLong function changes an attribute of the specified window.
The function also sets the 32-bit (long) value at the specified offset into the extra window memory.
CallWindowProc The CallWindowProc function passes message information to the specified window procedure
GetDriveType The GetDriveType function determines whether a disk drive is a removable, fixed, CD-ROM, RAM disk, or network drive
RtlMoveMemory The RtlMoveMemory routine moves memory either forward or backward, aligned or unaligned, in 4-byte blocks, followed by any remaining bytes
GetDWord The GetDWORD method retrieves a DWORD property
GetWord GetWORD method retrieves a WORD property
DeviceIoControl The DeviceIoControl function sends a control code directly to a specified device driver, causing the corresponding device to perform the corresponding operation.
CreateFile The CreateFile function creates or opens the following objects and returns a handle that can be used to access the object: → files → pipes → mailslots → communications resources → disk devices (Windows NT only) → consoles → directories (open only)
CloseHandle The CloseHandle function closes an open object handle.
RegisterDeviceNotification The RegisterDeviceNotification function registers the device or type of device for which a window will receive notifications
UnregisterDeviceNotification The UnregisterDeviceNotification function closes the specified device notification handle

The Needed API Types

To make all these APIs work properly, you need a couple of API Types, and several API Constants. In the sample program, you will be working with the following API Types:

API Type Name API Type Description/Usage
DEV_BROADCAST_HDR The DEV_BROADCAST_HDR structure is a standard header for information related to a device event reported through the WM_DEVICECHANGE message
DEV_BROADCAST_DEVICEINTERFACE The DEV_BROADCAST_DEVICEINTERFACE structure contains information about a class of devices

The Needed API Constants

You will need the following Constants in your sample program:

API Constant Name API Constant Description/Use
GWL_WNDPROC Use the GWL_WNDPROC constant to tell the SetWindowLong function that you want to change the address of the target window’s WindowProc function
WM_DEVICECHANGE The WM_DEVICECHANGE device message notifies an application of a change to the hardware configuration of a device or the computer
DBT_DEVICEARRIVAL The system broadcasts the DBT_DEVICEARRIVAL device event when a device or piece of media has been inserted and becomes available
DBT_DEVICEREMOVECOMPLETE The system broadcasts the DBT_DEVICEREMOVECOMPLETE device event when a device or piece of media has been physically removed
DBT_DEVTYP_VOLUME The application must check the event to ensure that the type of device arriving is a volume. Logical volume
DBT_DEVTYP_DEVICEINTERFACE Device interface class
IOCTL_STORAGE_EJECT_MEDIA Causes media to be ejected from a SCSI device
GENERIC_READ Read Access
FILE_SHARE_READ Subsequent open operations on the object will succeed only if read access is requested
FILE_SHARE_WRITE Subsequent open operations on the object will succeed only if write access is requested
OPEN_EXISTING Opens the file
INVALID_HANDLE_VALUE If the function fails, the return value is INVALID_HANDLE_VALUE
DEVICE_NOTIFY_WINDOW_HANDLE Handle to the window or service that will receive device events for the devices specified in the NotificationFilter parameter
DBT_DEVTYP_DEVICEINTERFACE Device interface class
DEVICE_NOTIFY_ALL_INTERFACE_CLASSES Notifies the recipient of device interface events for all device interface classes

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