io-streams

Overview

The io-streams library contains simple and easy-to-use primitives for I/O using streams. Most users will want to import the top-level convenience module System.IO.Streams, which re-exports most of the library:

import System.IO.Streams (InputStream, OutputStream) import qualified System.IO.Streams as Streams

For first-time users, io-streams comes with an included tutorial, which can be found in the System.IO.Streams.Tutorial module.

Features

The io-streams user API has two basic types: InputStream a and OutputStream a, and three fundamental I/O primitives:

-- read an item from an input stream Streams.read :: InputStream a -> IO (Maybe a) -- push an item back to an input stream Streams.unRead :: a -> InputStream a -> IO () -- write to an output stream Streams.write :: Maybe a -> OutputStream a -> IO ()

Streams can be transformed by composition and hooked together with provided combinators:

ghci> Streams.fromList [1,2,3::Int] >>= Streams.map (*10) >>= Streams.toList [10,20,30]

Stream composition leaves the original stream accessible:

ghci> input <- Streams.fromByteString "long string" ghci> wrapped <- Streams.takeBytes 4 input ghci> Streams.read wrapped Just "long" ghci> Streams.read wrapped Nothing ghci> Streams.read input Just " string"

Simple types and operations in the IO monad mean straightforward and simple exception handling and resource cleanup using Haskell standard library facilities like Control.Exception.bracket.

io-streams comes with:

functions to use files, handles, concurrent channels, sockets, lists, vectors, and more as streams. a variety of combinators for wrapping and transforming streams, including compression and decompression using zlib, controlling precisely how many bytes are read from or written to a stream, buffering output using bytestring builders, folds, maps, filters, zips, etc. support for parsing from streams using attoparsec. support for spawning processes and communicating with them using streams.