Download a file from the internet to your hard drive. Updated January 28, 2006

See issue #136 and issue #141 of the Liberty BASIC Newsletter for articles on the usage.

'Download html from given
'URL to file on disk.
'
'Minimum availability Internet Explorer 3.0
'Minimum operating systems Windows NT 4.0, Windows 95
'

'check for valid URL for HTML page:
u$ = MultiByteToWideChar$("http://www.libertybasic.com/index.html")

if u$ = "" then
    print "Unable to convert URL to unicode string."
    end
end if

'if result = 0, URL is valid
result = ValidURL(u$)

if result = 0 then
    'download html from libertybasic.com
    downloadresult = DownloadToFile("http://www.libertybasic.com/index.html", DefaultDir$ + "\test.htm")
    if downloadresult <> 0 then print "Error downloading libertybasic.com HTML file."

    open DefaultDir$ + "\test.htm" for input as #f
    test$ = input$(#f, LOF(#f))
    close #f

    print test$ 'print HTML from file into mainwin
    print : print
    print "The text above was downloaded from http://www.libertybasic.com/"
else
    print "Invalid URL:"; u$
end if

'now attempt to download the banner:
result = DownloadToFile("http://www.libertybasic.com/lb3banner.jpg", DefaultDir$ + "\banner.jpg")
if result <> 0 then
    print "Error downloading Liberty BASIC banner."
else
    run "mspaint.exe " + chr$(34) + DefaultDir$ + "\banner.jpg" + chr$(34)
    print : print : print "Done"
end if

wait

Function DownloadToFile(urlfile$, localfile$)
    open "URLmon" for dll as #url
    calldll #url, "URLDownloadToFileA",_
    0 as long,_         'null
    urlfile$ as ptr,_   'url to download
    localfile$ as ptr,_ 'save file name
    0 as long,_         'reserved, must be 0
    0 as long,_         'callback address, can be 0
    DownloadToFile as ulong  '0=success
    close #url
end function

Function ValidURL(urlfile$)
    open "URLmon" for dll as #url
    calldll #url, "IsValidURL",_
    0 as long,_         'ignored, must be 0
    urlfile$ as ptr,_   'urlfile to check
    0 as ulong,_        'ignored, must be 0
    ValidURL as long
    close #url
end function


function MultiByteToWideChar$(String$)
    'converts any string into unicode
    CodePage = 0  :  dwFlags = 0
    cchMultiByte = -1
    lpMultiByteStr$ = String$
    cchWideChar = len(String$) * 3
    lpWideCharStr$ = space$(cchWideChar)

    calldll #kernel32, "MultiByteToWideChar", _
    CodePage as ulong, _    'CP_ACP=0, ansi code page
    dwFlags as ulong, _     'use 0, flags for character translation
    lpMultiByteStr$ as ptr,_'the ascii string to convert
    cchMultiByte as long, _ 'len of string, -1 for null-terminated string
    lpWideCharStr$ as ptr, _'buffer for returned ansi string
    cchWideChar as long, _  'size in wide characters of string buffer
    result as long          'returns number of wide characters written to buffer

    if result = 0 then
        MultiByteToWideChar$ = ""
    else
        MultiByteToWideChar$ = left$(lpWideCharStr$, result * 2)
    end if
    end function