URLOpenPullStream

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

This function creates a pull type stream object from a URL.

Syntax

HRESULT URLOpenPullStream(
  LPUNKNOWN pCaller,
  LPCSTR szURL,
  DWORD dwReserved,
  LPBINDSTATUSCALLBACK lpfnCB
);

Parameters

• pCaller
  Address of the controlling IUnknown interface of the calling Microsoft ActiveX component, if the caller is an ActiveX component. If the caller is not an ActiveX component, this value can be set to NULL. Otherwise, the caller is a Component Object Model (COM) object that is contained in another component, such as an ActiveX Control within the context of an HTML page. This parameter represents the outermost IUnknown of the calling component. The function attempts the download within the context of the ActiveX client framework and allows the caller's container to receive callbacks on the progress of the download.

• szURL
  String containing the URL to be converted to a stream object. This parameter cannot be NULL.

• dwReserved
  Reserved. Must be zero.

• lpfnCB
  Address of the caller's IBindStatusCallback interface, on which URLOpenPullStream calls IBindStatusCallback::OnDataAvailable when data arrives from the Internet. IBindStatusCallback::OnDataAvailable can return E_ABORT to abort the download.

Return Value

Returns S_OK if the operation succeeded or E_OUTOFMEMORY if there was insufficient memory to complete the operation.

Remarks

The pull model is slightly more cumbersome than the push model, but it allows the client to control the amount of Internet access for the download.

The data is downloaded from the Internet on demand. If not enough data is available locally to satisfy the requests, the IStream::Read call will not block until enough data has arrived. Instead, IStream::Read immediately returns E_PENDING and URLOpenPullStream requests the next packet of data from the Internet server.

Requirements