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|
module Network.HTTP.Semantics.ReadN (
-- * Reading n bytes
ReadN,
defaultReadN,
)
where
import qualified Data.ByteString as B
import Data.IORef
import Network.Socket
import qualified Network.Socket.ByteString as N
-- | Reading n bytes.
type ReadN = Int -> IO B.ByteString
-- | Naive implementation for readN.
--
-- /NOTE/: This function is intended to be used by a single thread only.
-- (It is probably quite rare anyway to want concurrent reads from the /same/
-- network socket.)
defaultReadN :: Socket -> IORef (Maybe B.ByteString) -> ReadN
defaultReadN _ _ 0 = return B.empty
defaultReadN s ref n = do
mbs <- readIORef ref
writeIORef ref Nothing
case mbs of
Nothing -> do
bs <- N.recv s n
if B.null bs
then return B.empty
else
if B.length bs == n
then return bs
else loop bs
Just bs
| B.length bs == n -> return bs
| B.length bs > n -> do
let (bs0, bs1) = B.splitAt n bs
writeIORef ref (Just bs1)
return bs0
| otherwise -> loop bs
where
loop bs = do
let n' = n - B.length bs
bs1 <- N.recv s n'
if B.null bs1
then return B.empty
else do
let bs2 = bs `B.append` bs1
if B.length bs2 == n
then return bs2
else loop bs2
|
