pCallerPointer to the controlling IUnknown interface of the calling Microsoft ActiveX component (if the caller is an ActiveX component). //控件的接口,如果不是控件则为0.
Pointer to a string value containing the URL to be downloaded. Cannot be set to NULL
Pointer to a string value containing the name of the file to create for bits that come from the download.
Reserved. Must be set to 0.
Pointer to the caller's IBindStatusCallback interface. URLDownloadToFile calls this interface's IBindStatusCallback::OnProgress method on a connection activity, including the arrival of data. IBindStatusCallback::OnDataAvailable is never called.
Returns one of the following values.
S_OK : The download started successfully.
E_OUTOFMEMORY: The buffer length is invalid, or there is insufficient memory to complete the operation.
INET_E_DOWNLOAD_FAILURE:The specified resource or callback interface was invalid.