A simple haskell file downloader (with stubbed main function)
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{-# LANGUAGE OverloadedStrings, BangPatterns #-} | |
import qualified Data.Maybe as M | |
import qualified Data.ByteString as BS | |
import qualified Data.ByteString.Char8 as C8 | |
import qualified Network.Http.Client as HTTP | |
import qualified System.Time as T | |
import qualified System.IO as IO | |
import qualified System.IO.Streams as S | |
import qualified System.IO.Streams.Combinators as SC | |
progressBar :: Int -> Int -> Int -> String | |
progressBar tot prog len = "[" ++ map outchar [1..len] ++ "]" | |
where cur = 1 + (prog * len `div` tot) :: Int | |
outchar n | n > cur = ' ' | |
| n == cur = '>' | |
| n < cur = '=' | |
type OutBS = S.OutputStream BS.ByteString | |
withProgressBar :: (Int -> Int -> String) -> Int -> (OutBS -> IO ()) -> (OutBS -> IO ()) | |
-- :: (S.OutputStream C8.ByteString -> IO a0) | |
withProgressBar progressFunc length outHandler outStream = do | |
T.TOD secs _ <- T.getClockTime | |
(fmap fst $ SC.outputFoldM acc (0, secs) outStream) >>= outHandler | |
where | |
acc :: (Int, Integer) -> BS.ByteString -> IO (Int, Integer) | |
acc (lastSize, lastSecs) bs = do | |
let !progress = lastSize + BS.length bs | |
T.TOD currSecs _ <- T.getClockTime | |
if currSecs > lastSecs || progress == length | |
then (IO.hPutStr IO.stderr $ '\r' : progressFunc length progress) >> IO.hFlush IO.stderr | |
else return () | |
return (progress, currSecs) | |
downloadFile :: HTTP.URL -> FilePath -> IO () | |
downloadFile url name = HTTP.get url $ \response inStream -> do | |
let totalLength = HTTP.getHeader response "Content-Length" | |
status tot prog = "\r" ++ name ++ " " ++ progressBar tot prog 50 ++ " " ++ show prog ++ "/" ++ show tot | |
maybeProgress = M.maybe id (withProgressBar status . fst . M.fromJust . C8.readInt ) totalLength | |
case HTTP.getStatusCode response of | |
200 -> S.withFileAsOutput name $ maybeProgress $ S.connect inStream | |
code -> error $ "Failed to download " ++ name ++ ": http response returned " ++ show code | |
main = downloadFile "http://mirror.internode.on.net/pub/videos/linus-dunked.avi" "linus-dunked.avi" |
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