Getting the main hardrive?

**DrSnuggles** · 02-02-2008

Hi, I'm using the volume serial of the harddrive for authorization of my program, I'm using the c:\ drive as default but some user do not have a c:\ drive so I need some way to check what the main hardrive is called. I'm using code like so:

Code:

DWORD dwVolSerial;
BOOL bIsRetrieved;
bIsRetrieved = GetVolumeInformation("C:\\",NULL,NULL,&dwVolSerial,NULL,NULL,NULL,NULL);
if (bIsRetrieved) 
{
	TSTR buf;
	buf.printf(_T("%u"),dwVolSerial);
	return new String(buf);
} 
return &undefined;

Any idea on how to expand on this code to also include such a check?

cheers,
CML

**Elysia** · 02-02-2008

Main drive is boot drive or windows drive?

**DrSnuggles** · 02-02-2008

Originally Posted by Elysia

Main drive is boot drive or windows drive?

Hi Elysia, I'm not quite sure what the difference is really. They are all windows systems so I guess I need the main drive where windows is installed.

**Elysia** · 02-02-2008

The computer has to boot from one hard drive, which is the boot drive.
However, Windows does not need to be installed on the boot drive.
The boot drive contains the OS boot loader, however.

To get the hard drive which Windows is installed on, try using the GetWindowsDirectory API. It will return the full path to the Windows directory, including drive and directory.

**DrSnuggles** · 02-02-2008

Thanks Elysia, I got that to work. For me that returns:
C:\WINDOWS

but the next problem is how do I split up that string to something I can pass to the GetVolumeInformation function? ("C:\\") I do not have much experience working with strings in Windows.

**Elysia** · 02-02-2008

Well, I'll demonstrate a C method because I don't really use std::string.

Code:

char Drive[4];
std::string WinDir = "C:\\WINDOWS";
memcpy(Drive, WinDir.c_str(), 3);
Drive[3] = 0;

I'm probably going to get flamed for this

Though I'm sure someone else will show a better solution.

**Dino** · 02-02-2008

In a line....

Code:

strcpy(Drive, WinDir.substr(0,3).c_str() ) ;

Todd

**Elysia** · 02-02-2008

In that case, why not

Code:

std::string strDrive = WinDir.substr(0,3);

?

**Dino** · 02-02-2008

I'm not familiar with the GetVolumeInformation() function, and whether it takes a c-string or a string. I assumed it took a c-string since that's what you had.

**Elysia** · 02-02-2008

Of course it does, but you only need to do .c_str() to get a C-style string.

**Dino** · 02-02-2008

Originally Posted by Todd

and whether it takes a c-string or a string.

Originally Posted by Elysia

Of course it does,

That's as clear as mud.

**Dino** · 02-02-2008

I looked it up. GetVolumeInformation takes a c-string.

**DrSnuggles** · 02-02-2008

Alright I got it working now, thanks a lot for the help, that was fast!
Here is what I ended up with. Note that TCHAR and TSTR are substitutes for char and C string. If you can see any issue let me know.

Code:

TCHAR infoBuf[32767];
if (GetWindowsDirectory(infoBuf, 32767))
{
	TSTR drive;
	drive.printf(_T("%s"),infoBuf);
	TSTR maindir = drive.Substr(0,3);
	DWORD dwVolSerial;
	BOOL bIsRetrieved = GetVolumeInformation(maindir,NULL,NULL,&dwVolSerial,NULL,NULL,NULL,NULL);
	if (bIsRetrieved) 
	{
		TSTR buf;
		buf.printf(_T("%u"),dwVolSerial);
		return new String(buf);
	} 
	return &undefined;
}
return &undefined;

**Elysia** · 02-02-2008

Originally Posted by Todd Burch

That's as clear as mud.

Sorry, I meant "of course it takes a C-string."

Originally Posted by Todd Burch

I looked it up. GetVolumeInformation takes a c-string.

All Windows API takes a C-string. No exceptions.

Originally Posted by DrSnuggles

Here is what I ended up with. Note that TCHAR and TSTR are substitutes for char and C string.

No, it's not. They are multi-byte/unicode "safe" macros that you can use to make the project compile with either unicode or multi-byte. But since you are using _T, all is well.

Code:

TCHAR infoBuf[32767];
if (GetWindowsDirectory(infoBuf, 32767))
{
	TSTR drive;
	drive.printf(_T("%s"),infoBuf);
	TSTR maindir = drive.Substr(0,3);
	DWORD dwVolSerial;
	BOOL bIsRetrieved = GetVolumeInformation(maindir,NULL,NULL,&dwVolSerial,NULL,NULL,NULL,NULL);
	if (bIsRetrieved) 
	{
		TSTR buf;
		buf.printf(_T("%u"),dwVolSerial);
		return new String(buf);
	} 
	return &undefined;
}
return &undefined;

[/QUOTE]

Side note: you can first call GetWindowsDirectory with no buffer and 0 for size. It will return the needed size to hold the path. You allocate that and then call it to make sure it works, whatever the length.
I'm pretty sure you can assign a string buffer to a std::string without the need of std::string.printf.
Also return NULL, not undefined if it fails.

**DrSnuggles** · 02-02-2008

Thanks for the tips Elysia. Yes those are indeed Unicode safe macros. The values I'm returning are actually values that are returned to the scripting language of the program I'm making the plugin for.(3ds max)

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