| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Data.ByteString.Streaming.HTTP
Description
This module replicates `pipes-http` as closely as will type-check, adding a
conduit-like http in ResourceT and a primitive simpleHTTP that emits
a streaming bytestring rather than a lazy one.
Here is an example GET request that streams the response body to standard output:
import qualified Data.ByteString.Streaming as Q import Data.ByteString.Streaming.HTTP main = do req <- parseRequest "https://www.example.com" m <- newManager tlsManagerSettings withHTTP req m $ \resp -> Q.stdout (responseBody resp)
Here is an example POST request that also streams the request body from standard input:
{-#LANGUAGE OverloadedStrings #-}
import qualified Data.ByteString.Streaming as Q
import Data.ByteString.Streaming.HTTP
main = do
req <- parseRequest "https://httpbin.org/post"
let req' = req
{ method = "POST"
, requestBody = stream Q.stdin
}
m <- newManager tlsManagerSettings
withHTTP req' m $ \resp -> Q.stdout (responseBody resp)Here is the GET request modified to use http and write to a file. runResourceT
manages the file handle and the interaction.
import qualified Data.ByteString.Streaming as Q
import Data.ByteString.Streaming.HTTP
main = do
req <- parseUrlThrow "https://www.example.com"
m <- newManager tlsManagerSettings
runResourceT $ do
resp <- http request manager
Q.writeFile "example.html" (responseBody resp) simpleHTTP can be used in ghci like so:
ghci> runResourceT $ Q.stdout $ Q.take 137 $ simpleHTTP "http://lpaste.net/raw/13" -- Adaptation and extension of a parser for data definitions given in -- appendix of G. Huttons's paper - Monadic Parser Combinators. --
Synopsis
- withHTTP :: Request -> Manager -> (Response (ByteString IO ()) -> IO a) -> IO a
- http :: MonadResource m => Request -> Manager -> m (Response (ByteString m ()))
- streamN :: Int64 -> ByteString IO () -> RequestBody
- stream :: ByteString IO () -> RequestBody
- simpleHTTP :: MonadResource m => String -> ByteString m ()
- module Network.HTTP.Client
- module Network.HTTP.Client.TLS
- data ResourceT (m :: Type -> Type) a
- class MonadIO m => MonadResource (m :: Type -> Type) where
- liftResourceT :: ResourceT IO a -> m a
- runResourceT :: MonadUnliftIO m => ResourceT m a -> m a
Streaming Interface
http :: MonadResource m => Request -> Manager -> m (Response (ByteString m ())) Source #
streamN :: Int64 -> ByteString IO () -> RequestBody Source #
Create a RequestBody from a content length and an effectful ByteString
stream :: ByteString IO () -> RequestBody Source #
Create a RequestBody from an effectful ByteString
stream is more flexible than streamN, but requires the server to support
chunked transfer encoding.
ghci testing
simpleHTTP :: MonadResource m => String -> ByteString m () Source #
This is a quick method - oleg would call it 'unprofessional' - to bring a web page in view. It sparks its own internal manager and closes itself. Thus something like this makes sense
>>>runResourceT $ Q.putStrLn $ simpleHttp "http://lpaste.net/raw/12"chunk _ [] = [] chunk n xs = let h = take n xs in h : (chunk n (drop n xs))
but if you try something like
>>>rest <- runResourceT $ Q.putStrLn $ Q.splitAt 40 $ simpleHTTP "http://lpaste.net/raw/146532"import Data.ByteString.Streaming.HTTP
it will just be good luck if with
>>>runResourceT $ Q.putStrLn rest
you get the rest of the file:
import qualified Data.ByteString.Streaming.Char8 as Q main = runResourceT $ Q.putStrLn $ simpleHTTP "http://lpaste.net/raw/146532"
rather than
*** Exception: <socket: 13>: hGetBuf: illegal operation (handle is closed)
Since, of course, the handle was already closed by the first use of runResourceT.
The same applies of course to the more hygienic withHTTP above,
which permits one to extract an IO (ByteString IO r), by using splitAt or
the like.
The reaction of some streaming-io libraries was simply to forbid
operations like splitAt. That this paternalism was not viewed
as simply outrageous is a consequence of the opacity of the
older iteratee-io libraries. It is obvious that I can no more run an
effectful bytestring after I have made its effects impossible by
using runResourceT (which basically means closeEverythingDown).
I might as well try to run it after tossing my machine into the flames.
Similarly, it is obvious that I cannot read from a handle after I have
applied hClose; there is simply no difference between the two cases.
re-exports
module Network.HTTP.Client
module Network.HTTP.Client.TLS
data ResourceT (m :: Type -> Type) a #
The Resource transformer. This transformer keeps track of all registered
actions, and calls them upon exit (via runResourceT). Actions may be
registered via register, or resources may be allocated atomically via
allocate. allocate corresponds closely to bracket.
Releasing may be performed before exit via the release function. This is a
highly recommended optimization, as it will ensure that scarce resources are
freed early. Note that calling release will deregister the action, so that
a release action will only ever be called once.
Since 0.3.0
Instances
class MonadIO m => MonadResource (m :: Type -> Type) where #
A Monad which allows for safe resource allocation. In theory, any monad
transformer stack which includes a ResourceT can be an instance of
MonadResource.
Note: runResourceT has a requirement for a MonadUnliftIO m monad,
which allows control operations to be lifted. A MonadResource does not
have this requirement. This means that transformers such as ContT can be
an instance of MonadResource. However, the ContT wrapper will need to be
unwrapped before calling runResourceT.
Since 0.3.0
Methods
liftResourceT :: ResourceT IO a -> m a #
Lift a ResourceT IO action into the current Monad.
Since 0.4.0
Instances
runResourceT :: MonadUnliftIO m => ResourceT m a -> m a #
Unwrap a ResourceT transformer, and call all registered release actions.
Note that there is some reference counting involved due to resourceForkIO.
If multiple threads are sharing the same collection of resources, only the
last call to runResourceT will deallocate the resources.
NOTE Since version 1.2.0, this function will throw a
ResourceCleanupException if any of the cleanup functions throw an
exception.
Since: resourcet-0.3.0