Conversion of physical drive paths using C++ - c++

Question

I'm using WMI to retrieve information about physical drives on the system:
SELECT * FROM Win32_PhysicalMedia
And the "Tag" property returns physical device paths such as "\.\PHYSICALDRIVE0", or "\.\CDROM0", etc.
Is there a way to associate it with the actual drive paths, stuff like "C:" or "D:" or at least a device path "\Device\HarddiskVolume1"?
PS. In despite of my use of WMI, I'm writing the code using WinAPIs and C++.
EDIT:
Below is how it's done in C++. Note that this code should not be called right-when-you-need-this because it is extremely slow. What I would do is run it in a worker thread when the app starts and cache it somewhere for later user. I'd also watch for the WM_DEVICECHANGE notification and rerun it if drive layout changes.
Whew. I know it's complicated ... but, hey, it's Windows.
The code below comes from comments to this page.
#define _WIN32_DCOM
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>
#pragma comment(lib, "wbemuuid.lib")
BOOL wmi_run();
BOOL wmi_getDriveLetters();
BOOL wmi_close();
IWbemLocator *pLoc = NULL;
IWbemServices *pSvc = NULL;
int main(int argc, char **argv)
{
wmi_run();
wmi_getDriveLetters();
system("pause");
wmi_close();
}
//
// Step 1-5 at:
// http://msdn.microsoft.com/en-us/library/aa390423(VS.85).aspx
BOOL wmi_run()
{
HRESULT hres;
// Step 1: --------------------------------------------------
// Initialize COM. ------------------------------------------
hres = CoInitializeEx(0, COINIT_MULTITHREADED);
if (FAILED(hres))
{
cout << "Failed to initialize COM library. Error code = 0x"
<< hex << hres << endl;
return 1; // Program has failed.
}
// Step 2: --------------------------------------------------
// Set general COM security levels --------------------------
// Note: If you are using Windows 2000, you need to specify -
// the default authentication credentials for a user by using
// a SOLE_AUTHENTICATION_LIST structure in the pAuthList ----
// parameter of CoInitializeSecurity ------------------------
hres = CoInitializeSecurity(
NULL,
-1, // COM authentication
NULL, // Authentication services
NULL, // Reserved
RPC_C_AUTHN_LEVEL_DEFAULT, // Default authentication
RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation
NULL, // Authentication info
EOAC_NONE, // Additional capabilities
NULL // Reserved
);
if (FAILED(hres))
{
cout << "Failed to initialize security. Error code = 0x"
<< hex << hres << endl;
CoUninitialize();
return 1; // Program has failed.
}
// Step 3: ---------------------------------------------------
// Obtain the initial locator to WMI -------------------------
//IWbemLocator *pLoc = NULL;
hres = CoCreateInstance(
CLSID_WbemLocator,
0,
CLSCTX_INPROC_SERVER,
IID_IWbemLocator, (LPVOID *) &pLoc);
if (FAILED(hres))
{
cout << "Failed to create IWbemLocator object."
<< " Err code = 0x"
<< hex << hres << endl;
CoUninitialize();
return 1; // Program has failed.
}
// Step 4: -----------------------------------------------------
// Connect to WMI through the IWbemLocator::ConnectServer method
//IWbemServices *pSvc = NULL;
// Connect to the root\cimv2 namespace with
// the current user and obtain pointer pSvc
// to make IWbemServices calls.
hres = pLoc->ConnectServer(
_bstr_t(L"ROOT\\CIMV2"), // Object path of WMI namespace
NULL, // User name. NULL = current user
NULL, // User password. NULL = current
0, // Locale. NULL indicates current
NULL, // Security flags.
0, // Authority (e.g. Kerberos)
0, // Context object
&pSvc // pointer to IWbemServices proxy
);
if (FAILED(hres))
{
cout << "Could not connect. Error code = 0x"
<< hex << hres << endl;
pLoc->Release();
CoUninitialize();
return 1; // Program has failed.
}
cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;
// Step 5: --------------------------------------------------
// Set security levels on the proxy -------------------------
hres = CoSetProxyBlanket(
pSvc, // Indicates the proxy to set
RPC_C_AUTHN_WINNT, // RPC_C_AUTHN_xxx
RPC_C_AUTHZ_NONE, // RPC_C_AUTHZ_xxx
NULL, // Server principal name
RPC_C_AUTHN_LEVEL_CALL, // RPC_C_AUTHN_LEVEL_xxx
RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
NULL, // client identity
EOAC_NONE // proxy capabilities
);
if (FAILED(hres))
{
cout << "Could not set proxy blanket. Error code = 0x"
<< hex << hres << endl;
pSvc->Release();
pLoc->Release();
CoUninitialize();
return 1; // Program has failed.
}
return 0;
}
//
// get Drives, logical Drives and Driveletters
BOOL wmi_getDriveLetters()
{
// Use the IWbemServices pointer to make requests of WMI.
// Make requests here:
HRESULT hres;
IEnumWbemClassObject* pEnumerator = NULL;
// get localdrives
hres = pSvc->ExecQuery(
bstr_t("WQL"),
bstr_t("SELECT * FROM Win32_DiskDrive"),
WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
NULL,
&pEnumerator);
if (FAILED(hres)) {
cout << "Query for processes failed. "
<< "Error code = 0x"
<< hex << hres << endl;
pSvc->Release();
pLoc->Release();
CoUninitialize();
return FALSE; // Program has failed.
}
else {
IWbemClassObject *pclsObj;
ULONG uReturn = 0;
while (pEnumerator) {
hres = pEnumerator->Next(WBEM_INFINITE, 1,
&pclsObj, &uReturn);
if(0 == uReturn) break;
VARIANT vtProp;
hres = pclsObj->Get(_bstr_t(L"DeviceID"), 0, &vtProp, 0, 0);
// adjust string
wstring tmp = vtProp.bstrVal;
tmp = tmp.substr(4);
wstring wstrQuery = L"Associators of {Win32_DiskDrive.DeviceID='\\\\.\\";
wstrQuery += tmp;
wstrQuery += L"'} where AssocClass=Win32_DiskDriveToDiskPartition";
// reference drive to partition
IEnumWbemClassObject* pEnumerator1 = NULL;
hres = pSvc->ExecQuery(
bstr_t("WQL"),
bstr_t( wstrQuery.c_str()),
WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
NULL,
&pEnumerator1 );
if ( FAILED(hres) ) {
cout << "Query for processes failed. "
<< "Error code = 0x"
<< hex << hres << endl;
pSvc->Release();
pLoc->Release();
CoUninitialize();
return FALSE; // Program has failed.
} else {
IWbemClassObject *pclsObj1;
ULONG uReturn1 = 0;
while( pEnumerator1 ) {
hres = pEnumerator1->Next( WBEM_INFINITE, 1,
&pclsObj1, &uReturn1 );
if(0 == uReturn1) break;
// reference logical drive to partition
VARIANT vtProp1;
hres = pclsObj1->Get( _bstr_t(L"DeviceID"), 0, &vtProp1, 0, 0 );
wstring wstrQuery = L"Associators of {Win32_DiskPartition.DeviceID='";
wstrQuery += vtProp1.bstrVal;
wstrQuery += L"'} where AssocClass=Win32_LogicalDiskToPartition";
IEnumWbemClassObject* pEnumerator2 = NULL;
hres = pSvc->ExecQuery(
bstr_t("WQL"),
bstr_t(wstrQuery.c_str()),
WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
NULL,
&pEnumerator2 );
if ( FAILED(hres) ) {
cout << "Query for processes failed. "
<< "Error code = 0x"
<< hex << hres << endl;
pSvc->Release();
pLoc->Release();
CoUninitialize();
return FALSE; // Program has failed.
} else {
// get driveletter
IWbemClassObject *pclsObj2;
ULONG uReturn2 = 0;
while( pEnumerator2 ) {
hres = pEnumerator2->Next( WBEM_INFINITE, 1,
&pclsObj2, &uReturn2 );
if(0 == uReturn2) break;
VARIANT vtProp2;
hres = pclsObj2->Get( _bstr_t(L"DeviceID"), 0, &vtProp2, 0, 0 );
// print result
printf("%ls : %ls\n", vtProp.bstrVal, vtProp2.bstrVal);
VariantClear( &vtProp2 );
}
pclsObj1->Release();
}
VariantClear( &vtProp1 );
pEnumerator2->Release();
}
pclsObj->Release();
}
VariantClear( &vtProp );
pEnumerator1->Release();
}
}
pEnumerator->Release();
return TRUE;
}
BOOL wmi_close()
{
// Cleanup
// ========
pSvc->Release();
pLoc->Release();
CoUninitialize();
return 0; // Program successfully completed.
}

Answer 1

This MSDN article explains how to use WMI to get from a disk drive to a list of the drive letters on it (it's the final section of the page).
You can use Win32_DiskDrivePhysicalMedia to get from the physical media to the disk drive.
But if you actually want a list of partitions, why not start at Win32_LogicalDisk?