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|
--------------------------------------------------------------------
-- |
-- Module : Data.MessagePack.Feed
-- Copyright : (c) Hideyuki Tanaka, 2009
-- License : BSD3
--
-- Maintainer: tanaka.hideyuki@gmail.com
-- Stability : experimental
-- Portability: portable
--
-- Feeders for Stream Deserializers
--
--------------------------------------------------------------------
module Data.MessagePack.Feed(
-- * Feeder type
Feeder,
-- * Feeders
feederFromHandle,
feederFromFile,
feederFromString,
) where
import Control.Monad
import Data.ByteString (ByteString)
import qualified Data.ByteString as BS
import Data.IORef
import System.IO
-- | Feeder returns Just ByteString when bytes remains, otherwise Nothing.
type Feeder = IO (Maybe ByteString)
-- | Feeder from Handle
feederFromHandle :: Handle -> IO Feeder
feederFromHandle h = return $ do
bs <- BS.hGet h bufSize
if BS.length bs > 0
then return $ Just bs
else do
hClose h
return Nothing
where
bufSize = 4096
-- | Feeder from File
feederFromFile :: FilePath -> IO Feeder
feederFromFile path =
openFile path ReadMode >>= feederFromHandle
-- | Feeder from ByteString
feederFromString :: ByteString -> IO Feeder
feederFromString bs = do
r <- newIORef (Just bs)
return $ f r
where
f r = do
mb <- readIORef r
writeIORef r Nothing
return mb
|
