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c++winapibstr

How would you convert a std::string to BSTR*?

How would you convert a std::string to BSTR*? 

STDMETHODIMP CMyRESTApp::rest(BSTR data, BSTR* restr)
{
    RESTClient restclient;
    RESTClient::response resp = restclient.get(data);

    Log("Response Status code: %s", resp.code);
    Log("Response Body: %s", resp.body);

    *restr = // here
    return S_OK;
}

I need convert the resp.body and this then to be returned for the *restr here.

Solution

  • An ATL based approach is to use ATL::CComBSTR and then a Detach() (or CopyTo(...)) the resultant CComBSTR to the BSTR*

    Something like:

    CComBSTR temp(stlstr.c_str());
*restr = temp.Detach();

    Else in general for std::basic_string you can use the Win32 API Sys* family of functions, such as SysAllocStringByteLen and SysAllocString;

    // For the `const char*` data type (`LPCSTR`);
*restr = SysAllocStringByteLen(stlstr.c_str(), stlstr.size());


    // More suitable for OLECHAR
*restr = SysAllocString(stlwstr.c_str());

    OLECHAR depends on the target platform, but generally it is wchar_t.

    Given your code, the shortest snippet could just be;

    *restr = SysAllocStringByteLen(resp.body.c_str(), resp.body.size());

    Note these Windows API functions use the "usual" windows code page conversions, please see further MSDN documentation on how to control this if required.