{-# LANGUAGE Rank2Types #-} {-# LANGUAGE CPP #-} {-| This module defines a generic web application interface. It is a common protocol between web servers and web applications. The overriding design principles here are performance and generality. To address performance, this library is built on top of the conduit and blaze-builder packages. The advantages of conduits over lazy IO have been debated elsewhere and so will not be addressed here. However, helper functions like 'responseLBS' allow you to continue using lazy IO if you so desire. Generality is achieved by removing many variables commonly found in similar projects that are not universal to all servers. The goal is that the 'Request' object contains only data which is meaningful in all circumstances. Please remember when using this package that, while your application may compile without a hitch against many different servers, there are other considerations to be taken when moving to a new backend. For example, if you transfer from a CGI application to a FastCGI one, you might suddenly find you have a memory leak. Conversely, a FastCGI application would be well served to preload all templates from disk when first starting; this would kill the performance of a CGI application. This package purposely provides very little functionality. You can find various middlewares, backends and utilities on Hackage. Some of the most commonly used include: [warp] <http://hackage.haskell.org/package/warp> [wai-extra] <http://hackage.haskell.org/package/wai-extra> [wai-test] <http://hackage.haskell.org/package/wai-test> -} module Network.Wai ( -- * Types Application , Middleware , ResponseReceived -- * Request , Request , defaultRequest , RequestBodyLength (..) -- ** Request accessors , requestMethod , httpVersion , rawPathInfo , rawQueryString , requestHeaders , isSecure , remoteHost , pathInfo , queryString , requestBody , vault , requestBodyLength , requestHeaderHost , requestHeaderRange , lazyRequestBody -- * Response , Response , StreamingBody , FilePart (..) -- ** Response composers , responseFile , responseBuilder , responseLBS , responseStream , responseRaw -- * Response accessors , responseStatus , responseHeaders , responseToStream ) where import Blaze.ByteString.Builder (Builder, fromLazyByteString) import Blaze.ByteString.Builder (fromByteString) import Control.Monad (unless) import qualified Data.ByteString as B import qualified Data.ByteString.Lazy as L import qualified Data.ByteString.Lazy.Internal as LI import Data.ByteString.Lazy.Internal (defaultChunkSize) import Data.ByteString.Lazy.Char8 () import Data.Function (fix) import Data.Monoid (mempty) import qualified Network.HTTP.Types as H import Network.Socket (SockAddr (SockAddrInet)) import Network.Wai.Internal import qualified System.IO as IO import System.IO.Unsafe (unsafeInterleaveIO) ---------------------------------------------------------------- -- | Creating 'Response' from a file. responseFile :: H.Status -> H.ResponseHeaders -> FilePath -> Maybe FilePart -> Response responseFile = ResponseFile -- | Creating 'Response' from 'Builder'. -- -- Some questions and answers about the usage of 'Builder' here: -- -- Q1. Shouldn't it be at the user's discretion to use Builders internally and -- then create a stream of ByteStrings? -- -- A1. That would be less efficient, as we wouldn't get cheap concatenation -- with the response headers. -- -- Q2. Isn't it really inefficient to convert from ByteString to Builder, and -- then right back to ByteString? -- -- A2. No. If the ByteStrings are small, then they will be copied into a larger -- buffer, which should be a performance gain overall (less system calls). If -- they are already large, then blaze-builder uses an InsertByteString -- instruction to avoid copying. -- -- Q3. Doesn't this prevent us from creating comet-style servers, since data -- will be cached? -- -- A3. You can force blaze-builder to output a ByteString before it is an -- optimal size by sending a flush command. responseBuilder :: H.Status -> H.ResponseHeaders -> Builder -> Response responseBuilder = ResponseBuilder -- | Creating 'Response' from 'L.ByteString'. This is a wrapper for -- 'responseBuilder'. responseLBS :: H.Status -> H.ResponseHeaders -> L.ByteString -> Response responseLBS s h = ResponseBuilder s h . fromLazyByteString -- | Creating 'Response' from a stream of values. -- -- In order to allocate resources in an exception-safe manner, you can use the -- @bracket@ pattern outside of the call to @responseStream@. As a trivial -- example: -- -- @ -- app :: Application -- app req respond = bracket_ -- (putStrLn \"Allocating scarce resource\") -- (putStrLn \"Cleaning up\") -- $ respond $ responseStream status200 [] $ \\write flush -> do -- write $ fromByteString \"Hello\\n\" -- flush -- write $ fromByteString \"World\\n\" -- @ -- -- Note that in some cases you can use @bracket@ from inside @responseStream@ -- as well. However, placing the call on the outside allows your status value -- and response headers to depend on the scarce resource. -- -- Since 3.0.0 responseStream :: H.Status -> H.ResponseHeaders -> StreamingBody -> Response responseStream = ResponseStream -- | Create a response for a raw application. This is useful for \"upgrade\" -- situations such as WebSockets, where an application requests for the server -- to grant it raw network access. -- -- This function requires a backup response to be provided, for the case where -- the handler in question does not support such upgrading (e.g., CGI apps). -- -- In the event that you read from the request body before returning a -- @responseRaw@, behavior is undefined. -- -- Since 2.1.0 responseRaw :: (IO B.ByteString -> (B.ByteString -> IO ()) -> IO ()) -> Response -> Response responseRaw = ResponseRaw ---------------------------------------------------------------- -- | Accessing 'H.Status' in 'Response'. responseStatus :: Response -> H.Status responseStatus (ResponseFile s _ _ _) = s responseStatus (ResponseBuilder s _ _ ) = s responseStatus (ResponseStream s _ _ ) = s responseStatus (ResponseRaw _ res ) = responseStatus res -- | Accessing 'H.ResponseHeaders' in 'Response'. responseHeaders :: Response -> H.ResponseHeaders responseHeaders (ResponseFile _ hs _ _) = hs responseHeaders (ResponseBuilder _ hs _ ) = hs responseHeaders (ResponseStream _ hs _ ) = hs responseHeaders (ResponseRaw _ res) = responseHeaders res -- | Converting the body information in 'Response' to a @StreamingBody@. responseToStream :: Response -> ( H.Status , H.ResponseHeaders , (StreamingBody -> IO a) -> IO a ) responseToStream (ResponseStream s h b) = (s, h, ($ b)) responseToStream (ResponseFile s h fp (Just part)) = ( s , h , \withBody -> IO.withBinaryFile fp IO.ReadMode $ \handle -> withBody $ \sendChunk _flush -> do IO.hSeek handle IO.AbsoluteSeek $ filePartOffset part let loop remaining | remaining <= 0 = return () loop remaining = do bs <- B.hGetSome handle defaultChunkSize unless (B.null bs) $ do let x = B.take remaining bs sendChunk $ fromByteString x loop $ remaining - B.length x loop $ fromIntegral $ filePartByteCount part ) responseToStream (ResponseFile s h fp Nothing) = ( s , h , \withBody -> IO.withBinaryFile fp IO.ReadMode $ \handle -> withBody $ \sendChunk _flush -> fix $ \loop -> do bs <- B.hGetSome handle defaultChunkSize unless (B.null bs) $ do sendChunk $ fromByteString bs loop ) responseToStream (ResponseBuilder s h b) = (s, h, \withBody -> withBody $ \sendChunk _flush -> sendChunk b) responseToStream (ResponseRaw _ res) = responseToStream res ---------------------------------------------------------------- -- | The WAI application. -- -- Note that, since WAI 3.0, this type is structured in continuation passing -- style to allow for proper safe resource handling. This was handled in the -- past via other means (e.g., @ResourceT@). As a demonstration: -- -- @ -- app :: Application -- app req respond = bracket_ -- (putStrLn \"Allocating scarce resource\") -- (putStrLn \"Cleaning up\") -- (respond $ responseLBS status200 [] \"Hello World\") -- @ type Application = Request -> (Response -> IO ResponseReceived) -> IO ResponseReceived -- | Middleware is a component that sits between the server and application. It -- can do such tasks as GZIP encoding or response caching. What follows is the -- general definition of middleware, though a middleware author should feel -- free to modify this. -- -- As an example of an alternate type for middleware, suppose you write a -- function to load up session information. The session information is simply a -- string map \[(String, String)\]. A logical type signature for this middleware -- might be: -- -- @ loadSession :: ([(String, String)] -> Application) -> Application @ -- -- Here, instead of taking a standard 'Application' as its first argument, the -- middleware takes a function which consumes the session information as well. type Middleware = Application -> Application -- | A default, blank request. -- -- Since 2.0.0 defaultRequest :: Request defaultRequest = Request { requestMethod = H.methodGet , httpVersion = H.http10 , rawPathInfo = B.empty , rawQueryString = B.empty , requestHeaders = [] , isSecure = False , remoteHost = SockAddrInet 0 0 , pathInfo = [] , queryString = [] , requestBody = return B.empty , vault = mempty , requestBodyLength = KnownLength 0 , requestHeaderHost = Nothing , requestHeaderRange = Nothing } -- | Get the request body as a lazy ByteString. This uses lazy I\/O under the -- surface, and therefore all typical warnings regarding lazy I/O apply. -- -- Since 1.4.1 lazyRequestBody :: Request -> IO L.ByteString lazyRequestBody req = loop where loop = unsafeInterleaveIO $ do bs <- requestBody req if B.null bs then return LI.Empty else do bss <- loop return $ LI.Chunk bs bss