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Downloading Internet Files

Posted on 1998-01-23
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Last Modified: 2013-11-20
I am working on an application to download a file from the Internet. I can do this successfully via the http functions but I'd like to put the retrieved file into cache. Does anyone know how to use the URLDownloadToCacheFile() function? Is this the right one? Do I have to be connected to the Internet first before I use it? What gives this command an Internet context? Any sample code anywhere?
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Question by:rhans042197
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chensu earned 100 total points
ID: 1314638
Yes, the URLDownloadToCacheFile() function is the right one. The latest Internet Client SDK has more information about the 4th parameter.

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

A simple example:

TCHAR pszFilename[MAX_PATH];

HRESULT hr = ::URLDownloadToCacheFile(NULL,  // for non ActiveX component
                                      _T("http://www.somewhere.com/somefile.dat"),
                                      pszFilename,
                                      URLOSTRM_USECACHEDCOPY,
                                      0,
                                      NULL);

if (SUCCEEDED(hr))
{
    // the file has been successfully downloaded, pszFilename contains the cached file name
}

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