c - 获取属性的日期值

Question

我目前正在编写一个必须执行 WMI 查询的 C 程序。我可以毫无问题地发出查询，但是当它从 VARIANT 变量中检索属性值时，它开始变得非常困难。

我有一个巨大的 switch case，对于每个 case 我只想 wprintf 值(最终目的是检索 wchar_t 字符串中的值)。

到目前为止，对于整数类型，这还不是那么困难，但是对于日期时间类型，我根本没有办法。

这是我正在处理的示例(为了便于理解，没有进行功能检查，但我这样做了:

typedef struct cpwmi {
    IWbemLocator         *locator;
    IWbemServices        *services;
    IEnumWbemClassObject *results;
    IWbemClassObject     *result;
} cpwmi_s;

void CpWmi_Constructor(cpwmi_s *self)
{
    self->locator = NULL;
    self->services = NULL;
    self->results = NULL;
    self->result = NULL;
}

void CpWmi_Destructor(cpwmi_s *self)
{
    if (self->result) {
        self->result->lpVtbl->Release(self->result);
    }
    if (self->results) {
        self->results->lpVtbl->Release(self->results);
    }
    if (self->services) {
        self->services->lpVtbl->Release(self->services);
    }
    if (self->locator) {
        self->locator->lpVtbl->Release(self->locator);
    }
}


void CpWmi_MinimalExample(cpwmi_s *self)
{
    // Connection
    CoCreateInstance(&CLSID_WbemLocator, NULL, CLSCTX_INPROC_SERVER, &IID_IWbemLocator, &self->locator);

    BSTR ressource = SysAllocString(L"ROOT\\CIMV2");
    self->locator->lpVtbl->ConnectServer(self->locator, ressource, NULL, NULL, NULL, 0, NULL, NULL, &self->services);
    SysFreeString(ressource);

    // Issue WMI query
    BSTR query = SysAllocString(L"SELECT ReleaseDate FROM Win32_BIOS");
    BSTR language = SysAllocString(L"WQL");
    self->services->lpVtbl->ExecQuery(self->services, language, query, WBEM_FLAG_BIDIRECTIONAL, NULL, &self->results);
    SysFreeString(query);
    SysFreeString(language);

    // Go to first result
    ULONG   count = 0;
    self->results->lpVtbl->Next(self->results, WBEM_INFINITE, 1, &self->result, &count);

    // Get propperty's value
    BSTR    propertyName = SysAllocString(L"ReleaseDate");
    VARIANT propertyValue;
    CIMTYPE propertyType;
    self->result->lpVtbl->Get(self->result, propertyName, 0, &propertyValue, &propertyType, 0);
    wprintf(L"%s: ", propertyName);

    if (propertyValue.vt != VT_NULL && propertyValue.vt != VT_EMPTY) {
        switch (propertyType) {
            /* Many case here */
        case CIM_DATETIME:
            wprintf(L"%f", propertyValue.date);
            break;
        }
    }
    VariantClear(&propertyValue);
    wprintf(L"\n");
}

int main(void)
{
    cpwmi_s wmi;

    CpWmi_Constructor(&wmi);

    // initialize COM
    CoInitializeEx(NULL, COINIT_MULTITHREADED);
    CoInitializeSecurity(NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_DEFAULT, RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE, NULL);

    CpWmi_MinimalExample(&wmi);

    CpWmi_Destructor(&wmi);

    // unwind everything else we've allocated
    CoUninitialize();

    printf("Stop\n");
    getchar();
    return;
}

我希望有类似的东西

发布日期:20140401000000.000000+000

但我最终得到了

发布日期:-92559592126069970772275711289628980735378270670621907468943360.000000

我一定是误读了 msdn 文档或者不知道如何搜索/阅读，因为到目前为止，我不知道如何在 C 中执行此操作!我还担心 CIM_REFERENCE_TYPE、CIM_OBJECT_TYPE 等。

有没有人知道或知道这样做？

Answer 1

propertyValue.date 是double，它需要"%g" 打印格式，但它可能无效。尝试使用 bstrVal 值代替:

case CIM_DATETIME:
    //wprintf(L"%g\n", propertyValue.date);
    wprintf(L"%s\n", propertyValue.bstrVal);
    break;

^{请注意，在 Debug模式下，您可以将光标移到 propertyValue 上，它应该会显示包含在 propertyValue}

中的值