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2019.03.15 URLDownloadToFile with IBindStatusCallback and IHTTPSecurity 1

2019. 3. 15. 13:11

URLDownloadToFile with IBindStatusCallback and IHTTPSecurity

2019. 3. 15. 13:11 in text/window general

The last parameter of URLDownloadToFile and URLDownloadToCacheFile API is the pointer of IBindStatusCallback.
This paramter is optional, so you can just set NULL; however, in my experience, you have to implement IBindStatusCallback in many cases.

class CBindStatusCallback : public IBindStatusCallback , public IHttpSecurity
{
public:
CBindStatusCallback()
~CBindStatusCallback(){}

///// IUnknown methods
STDMETHOD_(ULONG,AddRef)()
{ return 1; } //non-heap-based objects:

STDMETHOD_(ULONG,Release)()
{ return 1; } //non-heap-based objects:

    STDMETHOD(QueryInterface)(
    /* [in] */ REFIID riid,
    /* [iid_is][out] */ void __RPC_FAR *__RPC_FAR *ppvObject);

///// IBindStatusCallback methods.
STDMETHOD(OnStartBinding)(
        /* [in] */ DWORD dwReserved,
        /* [in] */ IBinding __RPC_FAR *pib)
        { return E_NOTIMPL; }

Implement IUnknown interface

AddRef, Relase Method

You can implement this function according to official rule, but there is trick.
You can make this object local variable, then you don't need to worry about it's lifetime.
return non-zero value: it means this object will not be destroyed.

QueryInterface Method

HRESULT CBindStatusCallback::QueryInterface(
    /* [in] */ REFIID riid,
    /* [iid_is][out] */ void __RPC_FAR *__RPC_FAR *ppvObject)
{
if( !ppvObject)
  return E_INVALIDARG;

if( IID_IUnknown == riid )
  *ppvObject =static_cast<IBindStatusCallback*>(this);
else if( IID_IBindStatusCallback == riid)
  *ppvObject =static_cast<IBindStatusCallback*>(this);
else if( IID_IWindowForBindingUI == riid)
  *ppvObject =static_cast<IWindowForBindingUI*>(this);
else if( IID_IHttpSecurity == riid )
  *ppvObject =static_cast<IHttpSecurity*>(this);
else
{
  *ppvObject = NULL;
  return E_NOINTERFACE;
}

reinterpret_cast<IUnknown*>(*ppvObject)->AddRef();
return S_OK;

}

Implement IBindStatusCallback interface

You don't need to implement every method; you can actually write 'return E_NOTIMPL' in almost cases.
GetBindInfo method has crucial role.

You can set a code page.

If there is non English character in URL, it can be an issue depending on the OS language setting.

Also, You can set several options.

HRESULT CBindStatusCallback::GetBindInfo(
/* [out] */ DWORD __RPC_FAR *grfBINDF,
/* [unique][out][in] */ BINDINFO __RPC_FAR *pbindinfo)
{

*grfBINDF = BINDF_ASYNCHRONOUS;

DWORD cbSize = pbindinfo->cbSize;
memset(pbindinfo, 0, cbSize);
pbindinfo->cbSize = cbSize;
pbindinfo->dwCodePage = CP_UTF8;

return S_OK;

}

Implement IHttpSecurity interface

You can download files even though the sever has some security problems such as a self-signed certificate.

///// IWindowForBindingUI
HRESULT CBindStatusCallback::GetWindow(
/* [in] */ REFGUID rguidReason,
/* [out] */ HWND *phwnd)
{
return S_FALSE; // This indicate that no window is available.
}

///// IHttpSecurity
HRESULT CBindStatusCallback::OnSecurityProblem(
/* [in] */ DWORD dwProblem)
{
return S_OK; // Ignore securiy errors.
}