Read the Cache in VB

• Download demo project - 10.32 KB

Introduction

This easy method uses Wininet DLL to read a cache file. The demo uses a class object.

This algorithm requires use of InternetOpen function to initialize the DLL to read from the cache. INTERNET_FLAG_FROM_CACHE setting forces a new download of the requested files in calls to InternetOpenURL with a URL set. It reads the file and returns it. It closes all handles.

Private Const INTERNET_OPEN_TYPE_DIRECT = &H1
Private Const INTERNET_FLAG_FROM_CACHE = &H40

Public Function ReadCacheFile(url As String) As String
 

  Dim l&, Buffer$, hOpen&, hFile&, Result&
   
    l = 32768
    Buffer = Space(l)
    
    DoEvents
    
    hOpen = InternetOpen(UserAgent, INTERNET_OPEN_TYPE_DIRECT, _
                         vbNullString, vbNullString, INTERNET_FLAG_FROM_CACHE)


  
    hFile = InternetOpenUrl(hOpen, url, vbNullString, _
                            ByVal 0&, &0, _
                            ByVal 0&)
                            
    Call InternetReadFile(hFile, Buffer, l, Result&)
    Call InternetCloseHandle(hFile)
    Call InternetCloseHandle(hOpen)
    
    ReadCacheFile = Left$(StrConv(Buffer, vbUnicode), Result&)
    
End Function

This line is useful for obtaining unfiltered data such as for getting an applet:

ReadCacheFile = Left$(StrConv(Buffer, vbUnicode), Result&)

In the case of an applet, with conversion to UNICODE it works, without the conversion it will not.

History

• 21^st December, 2003: Initial post