function urldecode(str) -- Decode special chars in URLs such as %20
   str = string.gsub (str, "+", " ") 
   str = string.gsub (str, "%%(%x%x)", function(h) return string.char(tonumber(h,16)) end) 
   str = string.gsub (str, "\r\n", "\n") 
   return str 
end

function url_encode(str)
   str = string.gsub (str, "\n", "\r\n") 
   str = string.gsub (str, "([^%w ])", function (c) return string.format ("%%%02X", string.byte(c)) end) 
   str = string.gsub (str, " ", "+") 
   return str 
end

function parseURL(url)
   local ty = findpattern(url, '([a-zA-Z0-9-]*)://')
   ty = string.sub(ty, 0, string.len(ty) - 3)
   local dom = findpattern(url, '([a-zA-Z0-9-]*\.[a-zA-Z0-9-^/]*\.?[a-zA-Z0-9-]*/)', string.len(ty) + 4)
   dom = string.sub(dom, 0, string.len(dom) - 1)
   local pa = string.sub(url, string.len(ty) + string.len(dom) + 4)
   pos = -1
   while pos ~= nil do
      oldpos = pos
      pos = string.find(pa, '/', pos + 1)
   end
   local fi = string.sub(pa, oldpos + 1)
   pa = string.sub(pa, 0, string.len(pa) - string.len(fi))
   return ty, dom, pa, fi
end

function getContentLength(url)
   local urlType, urlDomain, urlPath, urlFile = parseURL(url)

   server = getIPFromDNS(urlDomain) -- get the IP for the server to connect to
   if IP=="-1" then gPrint("Error getting IP.\n") do return end end

   headersock = Socket.connect(server, 80)
   while not headersock:isConnected() do System.sleep(100) end

   bytesSent = headersock:send("GET "..urlPath..urlFile.." HTTP/1.0\r\n") -- using GET instead of HEAD to ensure we get the right headers
   bytesSent = headersock:send("User-Agent: pspRSS "..appVersion.."\r\n") -- just to be nice...
   bytesSent = headersock:send("HOST: "..urlDomain.."\r\n\r\n")

   local line, headers = " ", ""

   while headersock:isConnected() and string.find(line, "\r\n\r\n") == nil and not Controls.read():cross() do
      line = headersock:recv()
      headers = headers..line
      screen.waitVblankStart()
   end

   headersock:close()

   local redirect = string.find(headers, "HTTP.....302.*")
   if redirect ~= nil then
      urlStart = string.find(headers, " ", string.find(headers, "Location[:]")) + 1
      urlEnd = string.find(headers, "\n", urlStart) - 1
      newURL = string.sub(headers, urlStart, urlEnd)
      redir_log:write(url.." redirects to "..newURL..".\n")

      gPrint("Feed redirects to "..newURL..".\n")

      cL, hL = getContentLength(newURL)
      return cL, hL, newURL
   end

   local _, _, contentLength = string.find(headers, "[Cc][Oo][Nn][Tt][Ee][Nn][Tt][-][Ll][Ee][Nn][Gg][Tt][Hh][:][ ]*([0-9]*)")
   if contentLength == nil then Wlan.term() error("Invalid content length. Malformed headers?") end
   return contentLength, string.len(headers), url
end

function downloadFile(url, title, defaultFilename, isFeed)
   local urlType, urlDomain, urlPath, urlFile = parseURL(url)
   local contentLength, headerLength, url = getContentLength(url)
   local urlType, urlDomain, urlPath, urlFile = parseURL(url)

   if contentLength == nil then error("Invalid content length. Malformed headers? ("..url..")") end

   if isFeed then
      if title ~= "" then rssFilename = title..".xml" -- use title (for feeds)
      elseif title == "" then rssFilename = defaultFilename -- no title, use default file name (for enclosures)
      else rssFilename = urlFile end -- use file name
   else rssFilename = defaultFilename
   end

   --server = getIPFromDNSOld(urlDomain) -- get the IP for the server to connect to
   server = getIPFromDNS(urlDomain) -- get the IP for the server to connect to
   if IP=="-1" then gPrint("Error getting IP.\n") do return end end

   httpsock = Socket.connect(server, 80) -- connect to the server
   while not httpsock:isConnected() and not Controls.read():start() do System.sleep(100) end -- wait for the connection

   bytesSent = httpsock:send("GET "..urlPath..urlFile.." HTTP/1.0\r\n") -- HTTP 1.0 GET request
   bytesSent = httpsock:send("User-Agent: pspRSS "..appVersion.."\r\n") -- just to be nice...
   bytesSent = httpsock:send("host: "..urlDomain.."\r\n\r\n") -- HTTP 1.0 GET request

   if isFeed then fileToOpen = "feeds/"..fixFileName(rssFilename) -- get correct filename
   else fileToOpen = rssFilename end
   outfile = assert(io.open(fileToOpen, "w")) -- open output file

   filedata = ""

   while not Controls.read():square() do
      line = httpsock:recv() -- receive the next piece of the download
      filedata = filedata..line
      if string.len(filedata) >= headerLength then
         fileStart = string.find(filedata, "\r\n\r\n")+4
         outfile:write(string.sub(filedata, fileStart))
         break
      end
      screen.waitVblankStart()
   end

   size = fileStart
   while true do
      line = httpsock:recv() -- receive the next piece of the download
      outfile:write(line)
      size = size + string.len(line)
      if size >= tonumber(contentLength) and line == "" then break end
      screen.waitVblankStart()
   end

   size = outfile:seek("end")
   outfile:close()
   httpsock:close()
   if size ~= 0 then
      if size > 1048576 then gPrint("Saved ("..round(size/1048576, 2).." MB).\n")
      else gPrint("Saved ("..round(size/1024, 2).." KB).\n") end
   else
      gPrint("Download error.\n")
      --error("Download error.")
   end
end