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{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE PackageImports #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Snap.Util.GZip
( withCompression
, withCompression' ) where
import Blaze.ByteString.Builder
import qualified Codec.Compression.GZip as GZip
import qualified Codec.Compression.Zlib as Zlib
import Control.Concurrent
import Control.Applicative hiding (many)
import Control.Exception
import Control.Monad
import Control.Monad.Trans
import Data.Attoparsec.Char8 hiding (Done)
import qualified Data.ByteString.Lazy.Char8 as L
import Data.ByteString.Char8 (ByteString)
import Data.Maybe
import qualified Data.Set as Set
import Data.Set (Set)
import Data.Typeable
import Prelude hiding (catch, takeWhile)
----------------------------------------------------------------------------
import Snap.Internal.Debug
import Snap.Internal.Parsing
import Snap.Iteratee
import qualified Snap.Iteratee as I
import Snap.Types
------------------------------------------------------------------------------
-- | Runs a 'Snap' web handler with compression if available.
--
-- If the client has indicated support for @gzip@ or @compress@ in its
-- @Accept-Encoding@ header, and the @Content-Type@ in the response is one of
-- the following types:
--
-- * @application/x-javascript@
--
-- * @text/css@
--
-- * @text/html@
--
-- * @text/javascript@
--
-- * @text/plain@
--
-- * @text/xml@
--
-- * @application/x-font-truetype@
--
-- Then the given handler's output stream will be compressed,
-- @Content-Encoding@ will be set in the output headers, and the
-- @Content-Length@ will be cleared if it was set. (We can't process the
-- stream in O(1) space if the length is known beforehand.)
--
-- The wrapped handler will be run to completion, and then the 'Response'
-- that's contained within the 'Snap' monad state will be passed to
-- 'finishWith' to prevent further processing.
--
withCompression :: MonadSnap m
=> m a -- ^ the web handler to run
-> m ()
withCompression = withCompression' compressibleMimeTypes
------------------------------------------------------------------------------
-- | The same as 'withCompression', with control over which MIME types to
-- compress.
withCompression' :: MonadSnap m
=> Set ByteString
-- ^ set of compressible MIME types
-> m a
-- ^ the web handler to run
-> m ()
withCompression' mimeTable action = do
_ <- action
resp <- getResponse
-- If a content-encoding is already set, do nothing. This prevents
-- "withCompression $ withCompression m" from ruining your day.
when (not $ isJust $ getHeader "Content-Encoding" resp) $ do
let mbCt = getHeader "Content-Type" resp
debug $ "withCompression', content-type is " ++ show mbCt
case mbCt of
(Just ct) -> when (Set.member ct mimeTable) chkAcceptEncoding
_ -> return $! ()
getResponse >>= finishWith
where
chkAcceptEncoding = do
req <- getRequest
debug $ "checking accept-encoding"
let mbAcc = getHeader "Accept-Encoding" req
debug $ "accept-encoding is " ++ show mbAcc
let s = fromMaybe "" mbAcc
types <- liftIO $ parseAcceptEncoding s
chooseType types
chooseType [] = return $! ()
chooseType ("gzip":_) = gzipCompression "gzip"
chooseType ("compress":_) = compressCompression "compress"
chooseType ("x-gzip":_) = gzipCompression "x-gzip"
chooseType ("x-compress":_) = compressCompression "x-compress"
chooseType (_:xs) = chooseType xs
------------------------------------------------------------------------------
-- private following
------------------------------------------------------------------------------
------------------------------------------------------------------------------
compressibleMimeTypes :: Set ByteString
compressibleMimeTypes = Set.fromList [ "application/x-font-truetype"
, "application/x-javascript"
, "text/css"
, "text/html"
, "text/javascript"
, "text/plain"
, "text/xml" ]
------------------------------------------------------------------------------
gzipCompression :: MonadSnap m => ByteString -> m ()
gzipCompression ce = modifyResponse f
where
f = setHeader "Content-Encoding" ce .
setHeader "Vary" "Accept-Encoding" .
clearContentLength .
modifyResponseBody gcompress
------------------------------------------------------------------------------
compressCompression :: MonadSnap m => ByteString -> m ()
compressCompression ce = modifyResponse f
where
f = setHeader "Content-Encoding" ce .
setHeader "Vary" "Accept-Encoding" .
clearContentLength .
modifyResponseBody ccompress
------------------------------------------------------------------------------
-- FIXME: use zlib-bindings
gcompress :: forall a . Enumerator Builder IO a
-> Enumerator Builder IO a
gcompress = compressEnumerator GZip.compress
------------------------------------------------------------------------------
ccompress :: forall a . Enumerator Builder IO a
-> Enumerator Builder IO a
ccompress = compressEnumerator Zlib.compress
------------------------------------------------------------------------------
compressEnumerator :: forall a .
(L.ByteString -> L.ByteString)
-> Enumerator Builder IO a
-> Enumerator Builder IO a
compressEnumerator compFunc enum' origStep = do
let iter = joinI $ I.map fromByteString origStep
step <- lift $ runIteratee iter
writeEnd <- liftIO $ newChan
readEnd <- liftIO $ newChan
tid <- liftIO $ forkIO $ threadProc readEnd writeEnd
let enum = mapEnum fromByteString toByteString enum'
let outEnum = enum (f readEnd writeEnd tid step)
mapIter toByteString fromByteString outEnum
where
--------------------------------------------------------------------------
streamFinished :: Stream ByteString -> Bool
streamFinished EOF = True
streamFinished (Chunks _) = False
--------------------------------------------------------------------------
consumeSomeOutput :: Chan (Either SomeException (Stream ByteString))
-> Step ByteString IO a
-> Iteratee ByteString IO (Step ByteString IO a)
consumeSomeOutput writeEnd step = do
e <- lift $ isEmptyChan writeEnd
if e
then return step
else do
ech <- lift $ readChan writeEnd
either throwError
(\ch -> do
step' <- checkDone (\k -> lift $ runIteratee $ k ch)
step
consumeSomeOutput writeEnd step')
ech
--------------------------------------------------------------------------
consumeRest :: Chan (Either SomeException (Stream ByteString))
-> Step ByteString IO a
-> Iteratee ByteString IO a
consumeRest writeEnd step = do
ech <- lift $ readChan writeEnd
either throwError
(\ch -> do
step' <- checkDone (\k -> lift $ runIteratee $ k ch) step
if (streamFinished ch)
then returnI step'
else consumeRest writeEnd step')
ech
--------------------------------------------------------------------------
f _ _ _ (Error e) = Error e
f _ _ _ (Yield x _) = Yield x EOF
f readEnd writeEnd tid st@(Continue k) = Continue $ \ch ->
case ch of
EOF -> do
lift $ writeChan readEnd Nothing
x <- consumeRest writeEnd st
lift $ killThread tid
return x
(Chunks xs) -> do
mapM_ (lift . writeChan readEnd . Just) xs
step' <- consumeSomeOutput writeEnd (Continue k)
returnI $ f readEnd writeEnd tid step'
--------------------------------------------------------------------------
threadProc :: Chan (Maybe ByteString)
-> Chan (Either SomeException (Stream ByteString))
-> IO ()
threadProc readEnd writeEnd = do
stream <- getChanContents readEnd
let bs = L.fromChunks $ streamToChunks stream
let output = L.toChunks $ compFunc bs
runIt output `catch` \(e::SomeException) ->
writeChan writeEnd $ Left e
where
runIt (x:xs) = do
writeChan writeEnd (toChunk x) >> runIt xs
runIt [] = do
writeChan writeEnd $ Right EOF
--------------------------------------------------------------------------
streamToChunks [] = []
streamToChunks (Nothing:_) = []
streamToChunks ((Just x):xs) = x:(streamToChunks xs)
--------------------------------------------------------------------------
toChunk = Right . Chunks . (:[])
------------------------------------------------------------------------------
-- We're not gonna bother with quality values; we'll do gzip or compress in
-- that order.
acceptParser :: Parser [ByteString]
acceptParser = do
xs <- option [] $ (:[]) <$> encoding
ys <- many (char ',' *> encoding)
endOfInput
return $ xs ++ ys
where
encoding = skipSpace *> c <* skipSpace
c = do
x <- coding
option () qvalue
return x
qvalue = do
skipSpace
char ';'
skipSpace
char 'q'
skipSpace
char '='
float
return ()
coding = string "*" <|> takeWhile isCodingChar
isCodingChar ch = isDigit ch || isAlpha_ascii ch || ch == '-' || ch == '_'
float = takeWhile isDigit >>
option () (char '.' >> takeWhile isDigit >> pure ())
------------------------------------------------------------------------------
data BadAcceptEncodingException = BadAcceptEncodingException
deriving (Typeable)
------------------------------------------------------------------------------
instance Show BadAcceptEncodingException where
show BadAcceptEncodingException = "bad 'accept-encoding' header"
------------------------------------------------------------------------------
instance Exception BadAcceptEncodingException
------------------------------------------------------------------------------
parseAcceptEncoding :: ByteString -> IO [ByteString]
parseAcceptEncoding s =
case r of
Left _ -> throwIO BadAcceptEncodingException
Right x -> return x
where
r = fullyParse s acceptParser
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