URLOpenPullStream 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 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 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 cannot be NULL.

dwReserved

Reserved for future use. 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.

Function Information

Windows NT	Use version 4.0. Implemented as ANSI and Unicode functions.
Windows	Use Windows 95 and later. Implemented as ANSI and Unicode functions.
Header	Urlmon.h
Import Library	Urlmon.lib
Minimum availability	Internet Explorer 3.0