WMI Query C++

//From: http://msdn.microsoft.com/en-us/library/aa394175(v=vs.85).aspx

#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.
}