io-streams: Simple, composable, and easy-to-use stream I/O

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.System.IO.Streams.read :: System.IO.Streams.InputStream a -> IO (Maybe a)

-- push an item back to an input stream
Streams.System.IO.Streams.unRead :: a -> System.IO.Streams.InputStream a -> IO ()

-- write to an output stream
Streams.System.IO.Streams.write :: Maybe a -> System.IO.Streams.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.

ChangeLog

1.1.4.0

Widened attoparsec and text library dependencies to allow the latest versions.

1.1.3.0

Added System.IO.Streams.ByteString.takeExactly. Widened network dependency to include 2.3. Added a NoInteractiveTests flag to selectively disable some tests for environments where spawning interactive processes is impossible.

1.1.2.2

Allowed newest versions of the process, test-framework, and text libraries.

1.1.2.1

Fixed build error when compiled against attoparsec-0.10.0.x.

1.1.2.0

Added System.IO.Streams.Concurrent.makeChanPipe, to create a simple concurrent pipe between an InputStream/OutputStream pair.

1.1.1.0

Added System.IO.Streams.Network.socketToStreamsWithBufferSize, allowing control over the size of the receive buffers used when reading from sockets.

1.1.0.3

Fixed an inconsistent version upper bound in the test suite.

1.1.0.2

Fixed a typo in the tutorial.

1.1.0.1

A couple of Haddock markup fixes.

1.1.0.0

Reworked, simplified, and streamlined the internals of the library. Exports from System.IO.Streams.Internal relying on Sources and Sinks were deleted because they are no longer necessary: Source(..), Sink(..), defaultPushback, withDefaultPushback, nullSource, nullSink, singletonSource, simpleSource, sourceToStream, sinkToStream, generatorToSource, and consumerToSink.

1.0.2.2

Fixed a bug in which "takeBytes 0" was erroneously requesting input from the wrapped stream.

1.0.2.1

Fixed a compile error on GHC 7.0.x.

1.0.2.0

Added System.IO.Streams.Process (support for communicating with system processes using streams), added new functions to System.IO.Streams.Handle for converting io-streams types to System.IO.Handles. (Now you can pass streams from this library to places that expect Handles and everything will work.)

1.0.1.0

Added System.IO.Streams.Combinators.ignoreEof.

1.0.0.1

Fixed some haddock markup.

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Flags

Automatic Flags

Name	Description	Default
nointeractivetests	Do not run interactive tests	Disabled

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

Downloads

• io-streams-1.1.4.0.tar.gz [browse] (Cabal source package)
• Package description (as included in the package)

Maintainer's Corner

Package maintainers

• DougBeardsley, GregoryCollins

For package maintainers and hackage trustees

• edit package information

Candidates

• 1.5.1.0, 1.5.2.0, 1.5.2.1, 1.5.2.2