Liberty BASIC Community Wiki - Rss Parser in Liberty Basic

ozgur_erdiller Dec 4, 2009

Welcome to my tiny Rss parser...I'm trying to create a small rss reader in liberty basic...I don't have any scientific background about programming, but little bit of little bit of that, i'm enjoying my time to write small applications in Liberty Basic (or other basics, but i find liberty basic really basic about GUI applications, is it only me?). Well as i'm writing the code, i'm trying to purify it as much as i can...The code i provide here is able strip most rss tags and print to mainwin...I'll change it by time, to get adapted for a GUI, so i need to place parsed elements to some string variable with index...I hope this will work for all...

See the first part for the URL,receive code from Alycesrestaurant.com

'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:
url$="http://rss.cnn.com/rss/cnn_travel.rss"
uniUrl$ = MultiByteToWideChar$(url$)
 
if uniUrl$ = "" then
    print "Unable to convert URL to unicode string."
    end
end if
 
'if result = 0, URL is valid
result = ValidURL(uniUrl$)
 
if result = 0 then
    'download html from url
    Cursor Hourglass
    downloadresult = DownloadToFile(url$,"\temp.tmp") 'some temp dir and temp file...
    if downloadresult <> 0 then print "Error downloading ";url$
    Cursor Normal
else
    print "Invalid URL:"; url$
end if
'Now opening th rss file, and binding to local var...
'Will be array for future multiple rss...
 
open  "\temp.tmp" for input as #f
    rss$=input$ (#f, lof(#f))
    close #f
kill "\temp.tmp" 'keep the hardrive clean!
 
a= StripTags(rss$)
 
 
function StripTags(raw$)
'print only the tags starting with < and ending with >
'According to RSS 2.0 standart we have the following channel data..
'First, start with rss or xml declaration, version...Then
'Channel
'       |-Title       Required
'       |-Link        Required
'       |-Description Required
'
'       |-Language         Optional
'       |-Copyright        Optional
'       |-managingEditor   Optional
'       |-webMaster        Optional
'       |-pubDate          Optional
'       |-lastBuildDate    Optional
'       |-category         Optional
'       |-generator        Optional
'       |-docs             Optional
'       |-cloud            Optional
'       |-ttl              Optional
'       |-image            Optional-----------------------
'       |-rating           Optional                       |><url></url>
'       |-textInput        Optional                       |<title></title>
'       |-skipHours        Optional                       |<link></link>
'       |-skipDays         Optional                       |<width></width>
'                                                         |<height></height>
'                                                         |<description></description>
'
'
'
'
'
'
'
' Elements of items...Items are sub-elements of Channels btw...
'So
'Channel----
'           |---<item>
'           |---<item>
'           |---<item>
'           |---<item>
'                    |-Title
'                    |-Link
'                    |-Description
'                    |-Author
'                    |-Category
'                    |-Comments
'                    |-enclosure
'                    |-guid
'                    |-pubDate
'                    |-source
'But the point is that most rss feeds doesn't follow this sequence of tags...
'So, first, we'll remove the tags
'with the information attached to them, and we'll have TAG=Content type of arrays...
 
channeltags$="title,link,description,language,copyright,managingeditor,webmaster,pubdate,lastbuilddate,category,generator,docs,cloud,ttl,image,rating,textinput,skiphours,skipdays,"
itemtags$="title,link,description,author,category,comments,enclosure,guid,pubdate,source,"
 
while tagend<len(raw$)
 
tagstart=instr(raw$,"<",tagend)
tagend=instr(raw$,">",tagstart)
taglen=tagend-tagstart+1
'print mid$(raw$,leftbrack,taglen), rightbrack
 
    if instr(mid$(raw$,tagstart,taglen),"<channel>",0)>0 then
        chcount=1
        print "We found a channel! "
            while word$(channeltags$,chcount,",")<>""
 
 
              if instr(lower$(raw$),"<"+word$(channeltags$,chcount,",")+">")<>0 then
 
                    tagstart=instr(lower$(raw$),"<"+word$(channeltags$,chcount,",")+">")+len("<"+word$(channeltags$,chcount,",")+">")
                    tagend=instr(lower$(raw$),"</"+word$(channeltags$,chcount,",")+">",tagstart)
                    taglen=tagend-tagstart
                    print upper$(word$(channeltags$,chcount,","));">>>>";mid$(raw$,tagstart,taglen)
                    'here, if we have image, seperately we must parse it...
 
              end if
                    chcount=chcount+1
            wend
'Upto here, everything is working fine...Missing parts are GUID and media...image tag should be parsed independent...
            filepos=instr(raw$,"<item>")
 
            while instr(raw$,"<item>")<>0'Loop until there are no items left...
            'since channel is finished, cut the raw$ to only size of items...
            currentitem$=mid$(raw$,filepos-1,instr(raw$,"</item>"))
            raw$=right$(raw$,len(raw$)-instr(raw$,"/item>"))
            itemcount=1
            print "New item!"
            while word$(itemtags$,itemcount,",")<>""
 
                        if instr(lower$(currentitem$),"<"+word$(itemtags$,itemcount,",")+">")<>0 then
                           tagstart=instr(lower$(currentitem$),"<"+word$(itemtags$,itemcount,",")+">")+len("<"+word$(itemtags$,itemcount,",")+">")
                           tagend=instr(lower$(currentitem$),"</"+word$(itemtags$,itemcount,",")+">",tagstart)
                           taglen=tagend-tagstart
                           print upper$(word$(itemtags$,itemcount,","));">>>>";mid$(currentitem$,tagstart,taglen)
'                           print tagstart,tagend,taglen
                        end if
                    itemcount=itemcount+1
            filepos=1
            wend'single item
            wend'whole items...
 
    end if 'channel end if...
 
 
 
wend
 
'Upto here, everything is working fine...Missing parts are GUID and media
End Function
 
 
Function lowercase (string$)
lowercase$=lower$(string$)
End Function
 
 
 
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

Comments, advices, and any help on GUI is welcomed...Probably, i will need to deal with listview's little bit...Actually i have another idea to make the GUI, html based and show it in a lightweight browser...Not sure but again from Alycesrestaurant.com or lbpe.wikispaces.com...I'll find soon...
ozgur(.)erdiller(at)gmail(.)com