DeviceIOControl () fails with error 87

vasu_sri

hi everybody, iam using <b>DeviceIoControl()</b> to get the physical drive number. but the problem is that the DeviceIoControl is giving error 87.means that parameter is incoorect. please help me anybody knows this solution.

int GetDriveNumber(CString strDrive)
{
TCHAR lpWindowsDir[_MAX_PATH+1];
VOLUME_DISK_EXTENTS pdg;
CString strDevice;
HANDLE hDevice =NULL;
DWORD dw;
DWORD dwBytesReturned;
GetWindowsDirectory(lpWindowsDir,_MAX_PATH+1);

strDevice.Format(\_T("\\\\\\\\.\\\\%s:"),strDrive);
hDevice = CreateFile(strDevice,					// the device
	GENERIC\_READ,								// open for reading
	FILE\_SHARE\_READ|FILE\_SHARE\_WRITE,			// share mode
	NULL,										// default security
	OPEN\_EXISTING,								// open existing
	FILE\_ATTRIBUTE\_NORMAL,						// normal file
	NULL);		
if(hDevice != INVALID\_HANDLE\_VALUE)
{
	BOOL bIsSucces = DeviceIoControl(hDevice,IOCTL\_VOLUME\_GET\_VOLUME\_DISK\_EXTENTS,NULL,0,
		&amp;pdg,sizeof(pdg),&amp;dwBytesReturned,NULL);
	dw= GetLastError();

	CloseHandle(hDevice);
	return pdg.Extents-&gt;DiskNumber;
}
return FALSE;

}

Regards, Srinivas

David Crow

Your code worked fine for me. How are you calling GetDriveNumber()? Are you calling GetLastError() regardless of what DeviceIoControl() returns.

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Lost User

Hi Srinivas, What type of storage device are you using this control code on? You need to call GetLastError and check to see if the buffer you passed was too small. This control code can return an array greater than your buffer size. Best Wishes, -David Delaune

vasu_sri

i got it, where is the problem. i declared as #pragma pack(push, 1) in stdafx.h file. it is working perfect,if i removed #pragma pack(push, 1) in a stdafx.h file. but i need #pragma pack(push, 1) some where in my code, how can i disable this pragma pack1 through code. tell me if anybody knows this soultion thanks

Regards, Srinivas

Lost User

Hi Srinivas, You should only add this #pragma pack[^] around the structs,classes that require packing. After the struct/class declaration you add:#pragma pack(pop)
This will allow the other data types to have previous alignment. Best Wishes, -David Delaune