I think the docs are wrong, or perhaps we're misunderstanding them. Magnus is correct.
Attached is a test program which listens on two ports, 42000 (blocking IO) and 42001 (non-blocking). You can use netcat, telnet, etc, to send it data. The behavior is as Magnus describes: bytes from hGetNonBlocking are available immediately, while hGet waits for a full buffer (or EOF) before returning. This behavior obviously makes hGet unsuitable for enumHandle; my apologies for not understanding the problem sooner.
import Control.Concurrent (forkIO, threadDelay) import Control.Monad (forever, unless) import Control.Monad.Fix (fix) import qualified Data.ByteString as B import Network import System.IO main :: IO () main = do blockingSock <- listenOn (PortNumber 42000) nonblockingSock <- listenOn (PortNumber 42001) forkIO $ acceptLoop B.hGet blockingSock "Blocking" forkIO $ acceptLoop nonblockingGet nonblockingSock "Non-blocking" forever $ threadDelay 1000000 nonblockingGet :: Handle -> Int -> IO B.ByteString nonblockingGet h n = do hasInput <- catch (hWaitForInput h (-1)) (\_ -> return False) if hasInput then B.hGetNonBlocking h n else return B.empty acceptLoop :: (Handle -> Int -> IO B.ByteString) -> Socket -> String -> IO () acceptLoop get sock label = fix $ \loop -> do (h, _, _) <- accept sock putStrLn $ label ++ " client connected" bytesLoop (get h) putStrLn $ label ++ " EOF" loop bytesLoop :: (Int -> IO B.ByteString) -> IO () bytesLoop get = fix $ \loop -> do bytes <- get 20 unless (B.null bytes) $ do putStrLn $ "bytes = " ++ show bytes loop
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