I wrote application which give me info about my disk. But with one exception. I keep my application on desktop C:. Application give me right info about pendrive and disk E: but NOT FOR DISK C:.
When I copy my application on pendrive and run it (from pendrive) - i get right info about disk C: and E: but NOT FOR PENDRIVE.
Problem is in function GetVolumeInformation. This function give me wrong info (only for disk which i run my application from)
GetVolumeInformation( ListItem, volumeNameBuffer, MAX_PATH, & volumeSerialNumber, & maximumComponentLength, & fileSystemFlags, fileSystemNameBuffer, MAX_PATH );
In conclusion:
I have right info about all disk (DISK TYPE, SIZE)
and wrong info about parameters from GetVolumeInformation function but ONLY for disk which I run application from.
wrong info
right info
If I set the ListItem var to hold "C:", the code succeeds. If I then set this var to hold "D:" it fails, with FormatMessage and GetLastError reporting: The filename, directory name, or volume label syntax is incorrect.
If I instead set the var to hold "D:/" or "D:\\" then it succeeds. The same is true for all logical drive letters present in my system.
Having a closer look at the docs for GetVolumeInformation, we can see that the first parameter it expects is a string that holds the root directory of the volume to be described. Therefore, if you just pass C: or D: etc, you're passing the current directory of the drive concerned which may or may not be the root. If it's not the root, *boom*!
Also, on a side note - the volume serial number is a 32 bit number, typically displayed in hex notation. The following snippet formats it the same way that the dir command does.
printf("Vol ser#: '%X-%X'\n", (volumeSerialNumber>>16) , (volumeSerialNumber&0xFFFF) );
result
Vol ser#: 'AA25-7CEF'
As compared to either:
printf("Vol ser#: '%X'\n", volumeSerialNumber ); (result: Vol ser#: 'AA257CEF')
or
printf("Vol ser#: '%u'\n", volumeSerialNumber ); (result: Vol ser#: '2854583535')
Related
There is a WinAPI function GetProcessIoCounters that provides details of all I/O operations of a given process: number of read/write operations and number of bytes read/written since the process started. Most likely Task Manager uses this function to show these numbers:
Is there a relatively easy way to get the same or similar stats, but for the whole system since it started?
Please note, that it is not the same as enumerate all current processes and sum up results of GetProcessIoCounters, because there are processes that start, run for a while and finish. At the time when I call GetProcessIoCounters such processes don't exist anymore, but I would like to know the overall I/O of the system.
I intend to collect these stats every hour or so and log them into the database for future analysis and to help with debugging.
I'm looking for a method that works on Windows XP without WMI (we use a significantly cut-down Windows XP Embedded), but if such method exists only for later versions of Windows, please share it. Eventually it will be useful.
Update
I tried the DeviceIoControl(IOCTL_DISK_PERFORMANCE) method suggested by Jerry Coffin.
I had to run diskperf.exe -Y to make it work. I didn't even have to reboot, but without it DeviceIoControl was failing with GetLastError=31 (A device attached to the system is not functioning.) DeviceIoControl continued to work after reboot without the need to run diskperf.exe -Y again, but the first call to DeviceIoControl after reboot returned zeros in all fields (BytesRead, BytesWritten, ReadCount, WriteCount). Further calls returned non-zero stats. Obviously, there was some substantial disk activity when the system started, but it was not counted. So, it looks like that the first call to DeviceIoControl after reboot indeed enables/starts the counters.
If I run diskperf.exe -N, then DeviceIoControl stops working immediately without the need to reboot. When I run diskperf.exe -Y, then DeviceIoControl works fine again.
Now the question is: what diskperf.exe -Y does and how to do the same thing in my program?
Update 2
I exported the whole registry after diskperf.exe -Y and after diskperf.exe -N and looked for the difference. The only difference I could find was in one key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\PartMgr
"EnableCounterForIoctl"=dword:00000001
diskperf.exe -Y adds this key, diskperf.exe -N removes it.
I tried to add/delete this key directly into the registry.
If the key doesn't exist and DeviceIoControl doesn't work (after I run diskperf.exe -N) and I add this key like this:
reg add "HKLM\SYSTEM\CurrentControlSet\Services\PartMgr" /v EnableCounterForIoctl /t REG_DWORD /d 1
, then DeviceIoControl begins to work immediately.
If the key exists and DeviceIoControl works (after I run diskperf.exe -Y) and I delete this key like this:
reg delete "HKLM\SYSTEM\CurrentControlSet\Services\PartMgr" /v EnableCounterForIoctl
then DeviceIoControl continues to work and the returned statistics keeps growing. Until reboot.
diskperf.exe must be doing something else in addition to changing the registry value, something like forcing the flush/refresh of the registry. In my case I care about enabling these counters and it seems to work with the simple adding of the registry key.
You can get the data one disk at a time using DeviceIoControl, something like this:
#include <windows.h>
#include <iostream>
int main() {
HANDLE dev = CreateFile("\\\\.\\C:",
FILE_READ_ATTRIBUTES,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
0,
NULL);
DISK_PERFORMANCE disk_info { };
DWORD bytes;
if (dev == INVALID_HANDLE_VALUE) {
std::cerr << "Error opening disk\n";
return 1;
}
if (!DeviceIoControl(dev,
IOCTL_DISK_PERFORMANCE,
NULL,
0,
&disk_info,
sizeof(disk_info),
&bytes,
NULL))
{
std::cerr << "Failure in DeviceIoControl\n";
return 1;
}
std::cout.imbue(std::locale(""));
std::cout << "Bytes read: " << disk_info.BytesRead.QuadPart << "\n";
std::cout << "Bytes written: " << disk_info.BytesWritten.QuadPart << "\n";
}
For example, on my machine right now, this shows:
Bytes read: 15,768,173,568
Bytes written: 22,370,663,424
Experimentally, the results I'm getting look reasonable. For example, after plugging in a flash drive and opening a preview of some pictures on it, I get:
Bytes read: 3,956,736
Bytes written: 0
To get the data for all drives currently visible in the system, add a call to GetLogicalDrives or GetLogicalDriveStrings, and call code like this in a loop, but filling in the appropriate drive letter for each call.
This still isn't guaranteed to be all the data since the system was booted though. For example, if you eject a removable disk, information about what was read from/written to that drive is lost. If you plug it back in, you'll only get data about what was read/written since the last time it was plugged in.
I'm not at all sure you're going to be able to do a whole lot better than that though, at least without doing a fair amount of extra work to collect data periodically and keep track of when disks are ejected and inserted and such. When a disk is ejected, I suspect Windows pretty much throws away all the statistics about that drive, so if it's later plugged back in, Windows no longer has stats about what was done with it prior to ejection.
Likewise, if a disk has been ejected so it's not currently visible, this won't be able to open it to start with, so it won't be able to retrieve any stats about that drive either.
I'm trying to use GetDiskFreeSpaceEx in my C++ win32 application to get the total available bytes on the 'current' drive. I'm on Windows 7.
I'm using this sample code: http://support.microsoft.com/kb/231497
And it works! Well, almost. It works if I provide a drive, such as:
...
szDrive[0] = 'C'; // <-- specifying drive
szDrive[1] = ':';
szDrive[2] = '\\';
szDrive[3] = '\0';
pszDrive = szDrive;
...
fResult = pGetDiskFreeSpaceEx ((LPCTSTR)pszDrive,
(PULARGE_INTEGER)&i64FreeBytesToCaller,
(PULARGE_INTEGER)&i64TotalBytes,
(PULARGE_INTEGER)&i64FreeBytes);
fResult becomes true and i can go on to accurately calculate the number of free bytes available.
The problem, however, is that I was hoping to not have to specify the drive, but instead just use the 'current' one. The docs I found online (Here) state:
lpDirectoryName [in, optional]
A directory on the disk. If this parameter is NULL, the function uses the root of the current disk.
But if I pass in NULL for the Directory Name then GetDiskFreeSpaceEx ends up returning false and the data remains as garbage.
fResult = pGetDiskFreeSpaceEx (NULL,
(PULARGE_INTEGER)&i64FreeBytesToCaller,
(PULARGE_INTEGER)&i64TotalBytes,
(PULARGE_INTEGER)&i64FreeBytes);
//fResult == false
Is this odd? Surely I'm missing something? Any help is appreciated!
EDIT
As per JosephH's comment, I did a GetLastError() call. It returned the DWORD for:
ERROR_INVALID_NAME 123 (0x7B)
The filename, directory name, or volume label syntax is incorrect.
2nd EDIT
Buried down in the comments I mentioned:
I tried GetCurrentDirectory and it returns the correct absolute path, except it prefixes it with \\?\
it returns the correct absolute path, except it prefixes it with \\?\
That's the key to this mystery. What you got back is the name of the directory with the native api path name. Windows is an operating system that internally looks very different from what you are familiar with winapi programming. The Windows kernel has a completely different api, it resembles the DEC VMS operating system a lot. No coincidence, David Cutler used to work for DEC. On top of that native OS were originally three api layers, Win32, POSIX and OS/2. They made it easy to port programs from other operating systems to Windows NT. Nobody cared much for the POSIX and OS/2 layers, they were dropped at XP time.
One infamous restriction in Win32 is the value of MAX_PATH, 260. It sets the largest permitted size of a C string that stores a file path name. The native api permits much larger names, 32000 characters. You can bypass the Win32 restriction by using the path name using the native api format. Which is simply the same path name as you are familiar with, but prefixed with \\?\.
So surely the reason that you got such a string back from GetCurrentDirectory() is because your current directory name is longer than 259 characters. Extrapolating further, GetDiskFreeSpaceEx() failed because it has a bug, it rejects the long name it sees when you pass NULL. Somewhat understandable, it isn't normally asked to deal with long names. Everybody just passes the drive name.
This is fairly typical for what happens when you create directories with such long names. Stuff just starts falling over randomly. In general there is a lot of C code around that uses MAX_PATH and that code will fail miserably when it has to deal with path names that are longer than that. This is a pretty exploitable problem too for its ability to create stack buffer overflow in a C program, technically a carefully crafted file name could be used to manipulate programs and inject malware.
There is no real cure for this problem, that bug in GetDiskFreeSpaceEx() isn't going to be fixed any time soon. Delete that directory, it can cause lots more trouble, and write this off as a learning experience.
I am pretty sure you will have to retrieve the current drive and directory and pass that to the function. I remember attempting to use GetDiskFreeSpaceEx() with the directory name as ".", but that did not work.
I need help with one of my programs that pulls out available drives on a system and prints various information about the drives. I am using VC++ and am fairly new to C++ and need some high level inputs or example code from experienced programmers.
Here is my current source code:
#include "stdafx.h"
#include Windows.h
#include stdio.h
#include iostream
using namespace std;
int main()
{
// Initial Dummy drive
WCHAR myDrives[] = L" A";
// Get the logical drive bitmask (1st drive at bit position 0, 2nd drive at bit position 1... so on)
DWORD myDrivesBitMask = GetLogicalDrives();
// Verifying the returned drive mask
if(myDrivesBitMask == 0)
wprintf(L"GetLogicalDrives() failed with error code: %d\n", GetLastError());
else {
wprintf(L"This machine has the following logical drives:\n");
while(myDrivesBitMask) {
// Use the bitwise AND with 1 to identify
// whether there is a drive present or not.
if(myDrivesBitMask & 1) {
// Printing out the available drives
wprintf(L"drive %s\n", myDrives);
}
// increment counter for the next available drive.
myDrives[1]++;
// shift the bitmask binary right
myDrivesBitMask >>= 1;
}
wprintf(L"\n");
}
system("pause");
}
`
-Here is the output-
This machine has the following logical drives:
drive C
drive D
drive E
drive F
drive G
drive H
drive I
I need to output additional information about each drive (perhaps an example will tell the story in a shorter amount of time):
Drive – C:\
Drive Type: Fixed
Drive Ready Status: True
Volume Label: Boot Drive
File System Type : NTFS
Free Space: 30021926912
Total Drive Size: 240055742464
Drive – D:\
Drive Type: Fixed
Drive Ready Status: True
Volume Label: Application Data
File System Type : NTFS
Free Space: 42462507008
Total Drive Size: 240054693888
Which methods, libs api, etc. can I use to pull out drive type, drive status, volume label, file system type, free space, and total drive size?
*Side note, I noticed a defect with my pre-processor directives, specifically within the standard I/O header files. I know that is not the recommended way using printf and cout is type safe and the proper route to go but I couldn't figure out how to format output in cout as you would do in wprintf(L"drive %s\n", myDrives);.... so how would you do this with cout??
Thanks in advance.
You want to look at functions such as GetVolumeInformation to retrieve file system information such as free space and volume name.
GetDriveType will give you some basic information about the drive type, but USB thumb sticks and flash readers can give surprising results.
I'm not sure what you mean by "ready status". If you mean whether there is a valid volume in the drive, then you can try CreateFile with a path of "\\.\C:" to try and open the volume. If it fails then there is no volume (disk) present. This will be of use for SD card readers. To do this without an error dialog appearing you will need to call SetErrorMode(SEM_NOOPENFILEERRORBOX) first.
To check whether a drive is ready you may also use GetDiskFreeSpaceEx. If this fails, the drive is not ready/usable.
Here is some example code: http://pinvoke.net/default.aspx/coredll/GetDiskFreeSpaceEx.html
Given a device instance ID for a network card, I would like to know its MAC address. Example device instance ID on my system for integrated Intel Gigabit card:
PCI\VEN_8086&DEV_10CC&SUBSYS_00008086&REV_00\3&33FD14CA&0&C8
So far, the algorithm I have used works as follows:
Call SetupDiGetClassDevs with DIGCF_DEVICEINTERFACE.
Call SetupDiEnumDeviceInfo to get the returned device in a SP_DEVINFO_DATA.
Call SetupDiEnumDeviceInterfaces with GUID_NDIS_LAN_CLASS to get a device interface.
Call SetupDiGetDeviceInterfaceDetail for this returned device interface. This gets us the device path as a string: \\?\pci#ven_8086&dev_10cc&subsys_00008086&rev_00#3&33fd14ca&0&c8#{ad498944-762f-11d0-8dcb-00c04fc3358c}\{28fd5409-15bd-4c06-b62f-004d3a06f852}
At this point we have an address to the network card driver's interface. Open it with CreateFile using the result from #4.
Call DeviceIoControl with IOCTL_NDIS_QUERY_GLOBAL_STATS and OID of OID_802_3_PERMANENT_ADDRESS to get the MAC address.
This usually works, and has been used successfully on quite a large number of machines. However, it appears that a very select few machines have network drivers that aren't responding properly to the DeviceIoControl request in step #6; the problem persists even after updating network card drivers to the latest. These are newer, Windows 7-based computers. Specifically, DeviceIoControl completes successfully, but returns zero bytes instead of the expected six bytes containing the MAC address.
A clue seems to be on the MSDN page for IOCTL_NDIS_QUERY_GLOBAL_STATS:
This IOCTL will be deprecated in later operating system releases. You
should use WMI interfaces to query miniport driver information. For
more information see, NDIS Support for WMI.
-- perhaps newer network card drivers are no longer implementing this IOCTL?
So, how should I get this working? Is it possible there's an oversight in my approach and I'm doing something slightly wrong? Or do I need to take a much more different approach? Some alternate approaches seem to include:
Query Win32_NetworkAdapter WMI class: provides needed information but rejected due to horrible performance. See Fast replacement for Win32_NetworkAdapter WMI class for getting MAC address of local computer
Query MSNdis_EthernetPermanentAddress WMI class: appears to be the WMI replacement for IOCTL_NDIS_QUERY_GLOBAL_STATS and queries the OID directly from the driver - and this one works on the troublesome network driver. Unfortunately, the returned class instances only provide the MAC address and the InstanceName, which is a localized string like Intel(R) 82567LM-2 Gigabit Network Connection. Querying MSNdis_EnumerateAdapter yields a list which relates the InstanceName to a DeviceName, like \DEVICE\{28FD5409-15BD-4C06-B62F-004D3A06F852}. I'm not sure how to go from the DeviceName to the plug-and-play device instance ID (PCI\VEN_8086......).
Call GetAdaptersAddresses or GetAdaptersInfo (deprecated). The only non-localized identifier I can find in the return value is the adapter name, which is a string like {28FD5409-15BD-4C06-B62F-004D3A06F852} - same as the DeviceName returned by the WMI NDIS classes. So again, I can't figure out how to relate it to the device instance ID. I'm not sure if it would work 100% of the time either - e.g. for adapters without TCP/IP protocol configured.
NetBIOS method: requires specific protocols to be set up on the card so won't work 100% of time. Generally seems hack-ish, and not a way to relate to device instance ID anyway that I know of. I'd reject this approach.
UUID generation method: rejected for reasons I won't elaborate on here.
It seems like if I could find a way to get the "GUID" for the card from the device instance ID, I'd be well on my way with one of the remaining two ways of doing things. But I haven't figured out how yet. Otherwise, the WMI NDIS approach would seem most promising.
Getting a list of network cards and MAC addresses is easy, and there are several ways of doing it. Doing it in a fast way that lets me relate it to the device instance ID is apparently hard...
EDIT: Sample code of the IOCTL call if it helps anyone (ignore the leaked hFile handle):
HANDLE hFile = CreateFile(dosDevice.c_str(), 0, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL);
if (hFile == INVALID_HANDLE_VALUE) {
DWORD err = GetLastError();
wcout << "GetMACAddress: CreateFile on " << dosDevice << " failed." << endl;
return MACAddress();
}
BYTE address[6];
DWORD oid = OID_802_3_PERMANENT_ADDRESS, returned = 0;
//this fails too: DWORD oid = OID_802_3_CURRENT_ADDRESS, returned = 0;
if (!DeviceIoControl(hFile, IOCTL_NDIS_QUERY_GLOBAL_STATS, &oid, sizeof(oid), address, 6, &returned, NULL)) {
DWORD err = GetLastError();
wcout << "GetMACAddress: DeviceIoControl on " << dosDevice << " failed." << endl;
return MACAddress();
}
if (returned != 6) {
wcout << "GetMACAddress: invalid address length of " << returned << "." << endl;
return MACAddress();
}
The code fails, printing:
GetMACAddress: invalid address length of 0.
So the DeviceIoControl returns non-zero indicating success, but then returns zero bytes.
Here's one way to do it:
Call GetAdaptersAddresses to get a list of IP_ADAPTER_ADDRESSES structs
Iterate over each adapter and get its GUID from the AdapterName field (I'm not sure if this behaviour is guaranteed, but all the adapters in my system have a GUID here, and the documentation says the AdapterName is permanent)
For each adapter read the registry key from HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4D36E972-E325-11CE-BFC1-08002BE10318}\<the adapter GUID>\Connection\PnPInstanceID (if it exists) (got this idea from here; searching on Google that key seems to be well documented, so it's not likely to change)
From this key you get the device ID for the adapter (something like: PCI\VEN_14E4&DEV_16B1&SUBSYS_96B11849&REV_10\4&2B8260C3&0&00E4)
Do this for each adapter until you find a match. When you get your match just go back to the IP_ADAPTER_ADDRESSES and look at the PhysicalAddress field
Get a beer (optional)
It wouldn't be Windows if there weren't a million ways to do something!
I wound up using SetupDiGetDeviceRegistryProperty to read SPDRP_FRIENDLYNAME. If that's not found, then I read SPDRP_DEVICEDESC instead. Ultimately, this gets me a string like "VirtualBox Host-Only Ethernet Adapter #2". I then match this against the InstanceName property in the WMI NDIS classes (MSNdis_EthernetPermanentAddress WMI class). Both properties must be read in case there are multiple adapters sharing the same driver (i.e. "#2", "#3", etc.) - if there's only one adapter then SPDRP_FRIENDLYNAME isn't available, but if there is more than one then SPDRP_FRIENDLYNAME is required to differentiate them.
The method makes me a little nervous because I'm comparing what seems like a localized string, and there's no documentation that I've found that guarantees what I'm doing will always work. Unfortunately, I haven't found any better ways that are documented to work, either.
A couple other alternate methods involve groveling in undocumented registry locations. One method is spencercw's method, and the other would be to read SPDRP_DRIVER, which is the name of a subkey under HKLM\SYSTEM\CurrentControlSet\Control\Class. Underneath the driver key, look for the Linkage\Export value which then seems like it could be matched to the DeviceName property of the MSNdis_EnumerateAdapter class. But there's no documentation I could find that says these values can be legally matched. Furthermore, the only documentation I found about Linkage\Export was from the Win2000 registry reference and explicitly said that applications shouldn't rely on it.
Another method would be to look at my original question, step 4: "SetupDiGetDeviceInterfaceDetail for this returned device interface". The device interface path actually can be used to reconstruct the device path. Start with device interface path: \\?\pci#ven_8086&dev_10cc&subsys_00008086&rev_00#3&33fd14ca&0&c8#{ad498944-762f-11d0-8dcb-00c04fc3358c}\{28fd5409-15bd-4c06-b62f-004d3a06f852}. Then, remove everything before the final slash, leaving you with: {28fd5409-15bd-4c06-b62f-004d3a06f852}. Finally, prepend \Device\ to this string and match it against the WMI NDIS classes. Again, however, this seems to be undocumented and relying on an implementation detail of a device interface path.
In the end, the other methods I investigated had their own undocumented complications that sounded at least as serious as matching the SPDRP_FRIENDLYNAME / SPDRP_DEVICEDESC strings. So I opted for the simpler approach, which was to just match those strings against the WMI NDIS classes.
I guess you want to get the MAC address in order to implement some sort of DRM, inventory, or classification system, since you tried to get the permanent MAC address instead of the current one.
You seem to forget that there's even an administratively super-imposed MAC address (in other words: a "forced" MAC address).
Some drivers let you do this from the Device Property page, under the Advanced tab (for example: my Marvell network adapter let me do this), while some others don't let you do that (read: they don't support that property).
However, it all ends in a Registry value: HKLM\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}\xxxx\NetworkAddress, with a REG_SZ type.
Here you can set a different MAC address than the original one, in the form "01020304abcd" (6 bytes, plain hexadecimal, without : separators or 0x prefix).
After you set it, reboot the machine, and on power-up the new MAC address will have effect.
I happen to have a motherboard with two Marvell integrated NICs, and a NETGEAR USB WiFi NIC. The Marvell one supports changing the MAC address: if you set the NetworkAddress value in the Registry, you see the new value in the driver properties page, too, and it has effect immediately, without the need to restart (if you change it from device Property Page).
Here follows the results of reading the MAC address with different methods:
GetAdaptersInfo: new MAC address
IOCTL_NDIS_QUERY_GLOBAL_STATS: original MAC address
MSNdis_EthernetPermanentAddress: original MAC address
I tried adding the NetworkAddress value in the Registry for the NETGEAR USB WiFi NIC, and the results are:
GetAdaptersInfo: new MAC address
IOCTL_NDIS_QUERY_GLOBAL_STATS: new MAC address
MSNdis_EthernetPermanentAddress: new MAC address
The original MAC addres is gone.
So, in order to not be fooled by a "malicious" user, you always need to check the HKLM\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}\xxxx\NetworkAddress Registry value. If that is set, i guess it's better to not trust that Network Adapter at all, since it is up to the driver implementation to decide what will be presented to you using the different methods.
Some background for getting to that Registry key:
Microsoft documentation about the HKLM\SYSTEM\CurrentControlSet\Class key
According to the Microsoft documentation on that page,
There is a subkey for each class that is named using the GUID of the
setup class
So we choose the {4D36E972-E325-11CE-BFC1-08002BE10318} subkey (aka GUID_DEVCLASS_NET, defined in <devguid.h>, and further documented here)
Again, according to Microsoft documentation,
Each class subkey contains other subkeys known as software keys (or, driver keys) for each device instance of that class installed in the system. Each of these software keys is named by using a device instance ID, which is a base-10, four-digit ordinal value
The xxxx part is a 4-character textual representation of a positive integer, starting from 0
So, you can traverse the subkeys up from 0000, 0001, 0002, up to the number of network adapters in your system.
The documentation stops here: I didn't find any other documentation about the different registry values, or such.
However, in each of these subkeys, you can find REG_SZ values that can help you link the GetAdaptersInfo(), MSNdis_EthernetPermanentAddress, Win32_NetworkAdapter, and Device Instance ID worlds (and this answers your question).
The Registry values are:
DeviceInstanceID: its value is, no surprise, the Device Instance ID
NetCfgInstanceId: its value is the AdapterName member of the IP_ADAPTER_INFO struct, returned by GetAdaptersInfo(). It is also the GUID member of the Win32_NetworkAdapter WMI class.
Don't forget the NetworkAddress one: should a valid MAC address exist here, a driver may report it as the MAC address in use by GetAdaptersInfo(), MSNdis_EthernetPermanentAddress, and IOCTL_NDIS_QUERY_GLOBAL_STATS!
Then, as you already said, the only connection between the MSNdis_EthernetPermanentAddress WMI Class and the rest of the "world" is by its InstanceName member. You can relate it to the Description member of the IP_ADAPTER_INFO struct, returned by GetAdaptersInfo(). Although it may be a localized name, it seems to be unique for the system (For my two integrated Marvell NICs, the second one has a " #2" appended to its name).
Final note:
Said all the above, the user could choose to disable WMI...
I was wondering if there is a Windows API that can tell me if there is a empty CD is inside a CD-ROM/DVD-Rom drive.
I've already looked at GetVolumeInformation(), but that only brings back information on the actual CD-ROM drive, not the media that is inside it, if there's even a CD in it or not.
All I'm trying to do is see if there's a cd in the drive or not and return a boolean value.
Thanks for any help
Call GetFileAttributes() on the root directory. GetFileAttributes() is quite optimized as it's commonly used as a check whether a file or directory exists.
Another method is to call GetDiskFreeSpace, which (despite its name) also returns the total disk size.
The Shell also has some useful functions. SHGetDriveMedia will tell you what's loaded, but you should first call GetDriveType().
The API you're looking for is most probably IMAPI.
I think this article here could be of help for you http://msdn.microsoft.com/en-us/magazine/cc163992.aspx
You can use DeviceIoControl API passing IOCTL_STORAGE_CHECK_VERIFY as the dwIoControlCode. This will check if a particular disc drive is ready i. e. has a disc in it and, of course, the tray is closed. Check the DeviceIoControl MSDN documentation for more info on this function.
// FROM VISTA to ....
BOOL CDYesNo(WCHAR letter) {// like F
DWORD pdwMediaContent=0;
BOOL ret =1;
WCHAR catw[3]; // create wchar string
catw[0]=letter;
catw[1]=L':';
catw[2]=NULL; `enter code here`
HRESULT rcd=SHGetDriveMedia( catw, &pdwMediaContent);
//rcd normally is S_OK, maybe tested.
if(pdwMediaContent ==0) ret=0;
return ret; // 0=empty
}