wai-extra-0.1.2: Network/Wai/Parse.hs
{-# LANGUAGE CPP #-}
-- | Some helpers for parsing data out of a raw WAI 'Request'.
module Network.Wai.Parse
( parseQueryString
, parseCookies
, parseHttpAccept
, parseRequestBody
, Sink (..)
, lbsSink
, tempFileSink
, FileInfo (..)
#if TEST
, Bound (..)
, findBound
, sinkTillBound
#endif
) where
import qualified Data.ByteString as S
import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString.Char8 as S8
import Data.Word (Word8)
import Data.Bits
import Data.Maybe (fromMaybe)
import Data.List (sortBy)
import Data.Function (on)
import System.Directory (removeFile, getTemporaryDirectory)
import System.IO (hClose, openBinaryTempFile, Handle)
import Network.Wai
uncons :: S.ByteString -> Maybe (Word8, S.ByteString)
uncons s
| S.null s = Nothing
| otherwise = Just (S.head s, S.tail s)
breakDiscard :: Word8 -> S.ByteString -> (S.ByteString, S.ByteString)
breakDiscard w s =
let (x, y) = S.break (== w) s
in (x, S.drop 1 y)
-- | Split out the query string into a list of keys and values. A few
-- importants points:
--
-- * There is no way to distinguish between a parameter with no value and a
-- parameter with an empty value. Eg, "foo=" and "foo" are the same.
--
-- * The result returned is still bytestrings, since we perform no character
-- decoding here. Most likely, you will want to use UTF-8 decoding, but this is
-- left to the user of the library.
--
-- * Percent decoding errors are ignored. In particular, "%Q" will be output as
-- "%Q".
parseQueryString :: S.ByteString -> [(S.ByteString, S.ByteString)]
parseQueryString q | S.null q = []
parseQueryString q =
let (x, xs) = breakDiscard 38 q -- ampersand
in parsePair x : parseQueryString xs
where
parsePair x =
let (k, v) = breakDiscard 61 x -- equal sign
in (qsDecode k, qsDecode v)
qsDecode :: S.ByteString -> S.ByteString
qsDecode z = fst $ S.unfoldrN (S.length z) go z
where
go bs =
case uncons bs of
Nothing -> Nothing
Just (43, ws) -> Just (32, ws) -- plus to space
Just (37, ws) -> Just $ fromMaybe (37, ws) $ do -- percent
(x, xs) <- uncons ws
x' <- hexVal x
(y, ys) <- uncons xs
y' <- hexVal y
Just $ (combine x' y', ys)
Just (w, ws) -> Just (w, ws)
hexVal w
| 48 <= w && w <= 57 = Just $ w - 48 -- 0 - 9
| 65 <= w && w <= 70 = Just $ w - 55 -- A - F
| 97 <= w && w <= 102 = Just $ w - 87 -- a - f
| otherwise = Nothing
combine :: Word8 -> Word8 -> Word8
combine a b = shiftL a 4 .|. b
-- | Decode the value of an HTTP_COOKIE header into key/value pairs.
parseCookies :: S.ByteString -> [(S.ByteString, S.ByteString)]
parseCookies s
| S.null s = []
| otherwise =
let (first, rest) = breakDiscard 59 s -- semicolon
in parseCookie first : parseCookies rest
parseCookie :: S.ByteString -> (S.ByteString, S.ByteString)
parseCookie s =
let (key, value) = breakDiscard 61 s -- equals sign
key' = S.dropWhile (== 32) key -- space
in (key', value)
-- | Parse the HTTP accept string to determine supported content types.
parseHttpAccept :: S.ByteString -> [S.ByteString]
parseHttpAccept = map fst
. sortBy (rcompare `on` snd)
. map grabQ
. S.split 44 -- comma
where
rcompare :: Double -> Double -> Ordering
rcompare = flip compare
grabQ s =
let (s', q) = breakDiscard 59 s -- semicolon
(_, q') = breakDiscard 61 q -- equals sign
in (trimWhite s', readQ $ trimWhite q')
readQ s = case reads $ S8.unpack s of
(x, _):_ -> x
_ -> 1.0
trimWhite = S.dropWhile (== 32) -- space
-- | A destination for data, the opposite of a 'Source'.
data Sink x y = Sink
{ sinkInit :: IO x
, sinkAppend :: x -> S.ByteString -> IO x
, sinkClose :: x -> IO y
, sinkFinalize :: y -> IO ()
}
lbsSink :: Sink ([S.ByteString] -> [S.ByteString]) L.ByteString
lbsSink = Sink
{ sinkInit = return id
, sinkAppend = \front bs -> return $ front . (:) bs
, sinkClose = \front -> return $ L.fromChunks $ front []
, sinkFinalize = \_ -> return ()
}
tempFileSink :: Sink (FilePath, Handle) FilePath
tempFileSink = Sink
{ sinkInit = do
tempDir <- getTemporaryDirectory
openBinaryTempFile tempDir "webenc.buf"
, sinkAppend = \(fp, h) bs -> S.hPut h bs >> return (fp, h)
, sinkClose = \(fp, h) -> do
hClose h
return fp
, sinkFinalize = \fp -> removeFile fp
}
-- | Information on an uploaded file.
data FileInfo c = FileInfo
{ fileName :: S.ByteString
, fileContentType :: S.ByteString
, fileContent :: c
}
deriving (Eq, Show)
type Param = (S.ByteString, S.ByteString)
type File y = (S.ByteString, FileInfo y)
parseRequestBody :: Sink x y
-> Request
-> IO ([Param], [File y])
parseRequestBody sink req = do
let ctype = do
ctype' <- lookup ReqContentType $ requestHeaders req
if urlenc `S.isPrefixOf` ctype'
then Just Nothing
else if formBound `S.isPrefixOf` ctype'
then Just $ Just $ S.drop (S.length formBound) ctype'
else Nothing
case ctype of
Nothing -> return ([], [])
Just Nothing -> do -- url-encoded
-- NOTE: in general, url-encoded data will be in a single chunk.
-- Therefore, I'm optimizing for the usual case by sticking with
-- strict byte strings here.
bs <- sourceToBs $ requestBody req
return (parseQueryString bs, [])
Just (Just bound) -> -- multi-part
let bound' = S8.pack "--" `S.append` bound
in parsePieces sink bound' (S.empty, Just $ requestBody req)
where
urlenc = S8.pack "application/x-www-form-urlencoded"
formBound = S8.pack "multipart/form-data; boundary="
sourceToBs :: Source -> IO S.ByteString
sourceToBs = fmap S.concat . go id
where
go front (Source src) = do
res <- src
case res of
Nothing -> return $ front []
Just (bs, src') -> go (front . (:) bs) src'
type Source' = (S.ByteString, Maybe Source)
takeLine :: Source' -> IO (Maybe (S.ByteString, Source'))
takeLine (s, msrc)
| S.null s = case msrc of
Nothing -> return Nothing
Just (Source src) -> do
res <- src
case res of
Nothing -> return Nothing
Just (x, y) -> takeLine (x, Just y)
takeLine (s, msrc) =
let (x, y) = S.break (== 10) s -- newline
in if S.null y
then do
case msrc of
Nothing -> return $ Just (x, (y, msrc))
Just (Source src) -> do
res <- src
case res of
Nothing -> return $ Just (x, (y, Nothing))
Just (s', src') ->
takeLine (s `S.append` s', Just src')
else return $ Just (killCarriage x, (S.drop 1 y, msrc))
where
killCarriage bs
| S.null bs = bs
| S.last bs == 13 = S.init bs -- carriage return
| otherwise = bs
takeLines :: Source' -> IO (Maybe ([S.ByteString], Source'))
takeLines src = do
res <- takeLine src
case res of
Nothing -> return Nothing
Just (l, src') ->
if S.null l
then return $ Just ([], src')
else do
res' <- takeLines src'
case res' of
Nothing -> return $ Just ([l], src')
Just (ls, src'') -> return $ Just (l : ls, src'')
parsePieces :: Sink x y -> S.ByteString -> Source'
-> IO ([Param], [File y])
parsePieces sink bound src = do
res <- takeLine src
src' <- case res of
Nothing -> return (S.empty, Nothing)
Just (_bs, src') -> return src'
res' <- takeLines src'
case res' of
Nothing -> return ([], [])
Just (ls, src'') -> do
let ls' = map parsePair ls
let x = do
cd <- lookup contDisp ls'
ct <- lookup contType ls'
let attrs = parseAttrs cd
let nameBS = S8.pack "name"
name <- lookup nameBS attrs
let fnBS = S8.pack "filename"
return (ct, name, lookup fnBS attrs)
case x of
Just (ct, name, Just filename) -> do
seed <- sinkInit sink
(seed', wasFound, msrc''') <-
sinkTillBound bound src'' (sinkAppend sink) seed
y <- sinkClose sink seed'
let fi = FileInfo filename ct y
let y' = (name, fi)
(xs, ys) <-
if wasFound
then parsePieces sink bound msrc'''
else return ([], [])
return (xs, y' : ys)
Just (_ct, name, Nothing) -> do
let seed = id
let iter front bs = return $ front . (:) bs
(front, wasFound, msrc''') <-
sinkTillBound bound src'' iter seed
let bs = S.concat $ front []
let x' = (name, qsDecode bs)
(xs, ys) <-
if wasFound
then parsePieces sink bound msrc'''
else return ([], [])
return (x' : xs, ys)
Nothing -> do
-- ignore this part
let seed = ()
iter () _ = return ()
((), wasFound, msrc''') <-
sinkTillBound bound src'' iter seed
if wasFound
then parsePieces sink bound msrc'''
else return ([], [])
where
contDisp = S8.pack "Content-Disposition"
contType = S8.pack "Content-Type"
parsePair s =
let (x, y) = breakDiscard 58 s -- colon
in (x, S.dropWhile (== 32) y) -- space
data Bound = FoundBound S.ByteString S.ByteString
| NoBound
| PartialBound
deriving (Eq, Show)
findBound :: S.ByteString -> S.ByteString -> Bound
findBound b bs = go [0..S.length bs - 1]
where
go [] = NoBound
go (i:is)
| mismatch [0..S.length b - 1] [i..S.length bs - 1] = go is
| otherwise =
let endI = i + S.length b
in if endI > S.length bs
then PartialBound
else FoundBound (S.take i bs) (S.drop endI bs)
mismatch [] _ = False
mismatch _ [] = False
mismatch (x:xs) (y:ys)
| S.index b x == S.index bs y = mismatch xs ys
| otherwise = True
sinkTillBound :: S.ByteString
-> Source'
-> (x -> S.ByteString -> IO x)
-> x
-> IO (x, Bool, Source')
sinkTillBound bound (bs, msrc) iter seed = do
case findBound bound bs of
NoBound -> do
case msrc of
Nothing -> do
seed' <- iter seed bs
return (seed', False, (S.empty, Nothing))
Just (Source src) -> do
res <- src
case res of
Nothing -> do
seed' <- iter seed bs
return (seed', False, (S.empty, Nothing))
Just (bs', src') -> do
-- this funny bit is to catch when there's a
-- newline at the end of the previous chunk
(seed', bs'') <-
if not (S8.null bs) && S8.last bs `elem` "\n\r"
then do
let (front, back) =
S.splitAt (S.length bs - 2) bs
seed' <- iter seed front
return (seed', back `S.append` bs')
else do
seed' <- iter seed bs
return (seed', bs')
sinkTillBound bound (bs'', Just src') iter seed'
FoundBound before after -> do
let before' = killCRLF before
seed' <- iter seed before'
return (seed', True, (after, msrc))
PartialBound -> do
-- not so efficient, but hopefully the unusual case
case msrc of
Nothing -> do
seed' <- iter seed bs
return (seed', False, (S.empty, Nothing))
Just (Source src) -> do
res <- src
case res of
Nothing -> do
seed' <- iter seed bs
return (seed', False, (S.empty, Nothing))
Just (bs', src') -> do
let bs'' = bs `S.append` bs'
sinkTillBound bound (bs'', Just src') iter seed
parseAttrs :: S.ByteString -> [(S.ByteString, S.ByteString)]
parseAttrs = map go . S.split 59 -- semicolon
where
tw = S.dropWhile (== 32) -- space
dq s = if S.length s > 2 && S.head s == 34 && S.last s == 34 -- quote
then S.tail $ S.init s
else s
go s =
let (x, y) = breakDiscard 61 s -- equals sign
in (tw x, dq $ tw y)
killCRLF :: S.ByteString -> S.ByteString
killCRLF bs
| S.null bs || S8.last bs /= '\n' = bs
| otherwise = killCR $ S.init bs
killCR :: S.ByteString -> S.ByteString
killCR bs
| S.null bs || S8.last bs /= '\r' = bs
| otherwise = S.init bs