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URLDownloadToCacheFile

HRESULT URLDownloadToCacheFile(
    LPUNKNOWN lpUnkcaller,
    LPCSTR szURL,
    LPTSTR szFileName,
    DWORD dwBufLength,
    DWORD dwReserved,
    IBindStatusCallback *pBSC
);

Downloads data into the Internet cache and returns the file name of the cache location for retrieving the bits. The client can choose to be notified of progress through a notification callback.

lpUnkcaller

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

URL to be downloaded. Cannot be NULL.

szFileName

Name of the downloaded file. Cannot be NULL.

dwBufLength

DWORD value that contains the size of the szFileName buffer or a flag. If a flag is set to dwBufLength, the buffer is assumed to be of size MAX_PATH. The flag can be one of the following values:

URLOSTRM_GETNEWESTVERSION	Download the resource from the Internet, if it is newer, and store it in the cache.
URLOSTRM_USECACHEDCOPY	Download the resource from the cache if it is available; otherwise, download it from the Internet.
URLOSTRM_USECACHEDCOPY_ONLY	Only download the resource from the cache.

dwReserved

Reserved. Must be set to zero.

pBSC

Address of the caller's IBindStatusCallback interface. URLDownloadToCacheFile calls this interface's IBindStatusCallback::OnProgress method on a connection activity, including the arrival of data. IBindStatusCallback::OnDataAvailable is never called. Implementing IBindStatusCallback::OnProgress allows a caller to implement a user interface or other progress monitoring functionality. It also allows the download operation to be canceled by returning E_ABORT from the IBindStatusCallback::OnProgress call. Can be NULL.

This function always returns a file name if the download operation succeeds. If the given URL is a "file:" URL, URLDownloadToCacheFile directly returns the file name for the "file:" URL rather than making a copy to the cache. If the given URL is an Internet URL ("http:", "ftp:"), URLDownloadToCacheFile downloads this file and returns the local file name of the cached copy. Using this function ensures that a file name is returned without unnecessary copying of data.

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