Data.Knob

Create memory-backed Handles, referencing virtual files. This is mostly useful for testing Handle-based APIs without having to interact with the filesystem.

import Data.ByteString (pack)
import Data.Knob
import System.IO

main = do
    knob <- newKnob (pack [])
    h <- newFileHandle knob "test.txt" WriteMode
    hPutStrLn h "Hello world!"
    hClose h
    bytes <- Data.Knob.getContents knob
    putStrLn ("Wrote bytes: " ++ show bytes)

Documentation

data Knob

A knob is a basic virtual file, which contains a byte buffer. A knob can have multiple Handles open to it, each of which behaves like a standard file handle.

Use getContents and setContents to inspect and modify the knob's byte buffer.

newKnob :: MonadIO m => ByteString -> m Knob

getContents :: MonadIO m => Knob -> m ByteString

setContents :: MonadIO m => Knob -> ByteString -> m ()

newFileHandle

Arguments

:: MonadIO m

=> Knob

-> String

Filename shown in error messages

-> IOMode

-> m Handle

Create a new Handle pointing to a Knob. This handle behaves like a file-backed handle for most purposes.

withFileHandle

Arguments

:: MonadIO m

=> Knob

-> String

Filename shown in error messages.

-> IOMode

-> (Handle -> IO a)

-> m a

See newFileHandle.

data Device

An IO device backed by a Knob. You shouldn't usually use this type directly; use newFileHandle or withFileHandle instead.

Instances

BufferedIO Device

Defined in Data.Knob

Methods

newBuffer :: Device -> BufferState -> IO (Buffer Word8)

fillReadBuffer :: Device -> Buffer Word8 -> IO (Int, Buffer Word8)

fillReadBuffer0 :: Device -> Buffer Word8 -> IO (Maybe Int, Buffer Word8)

emptyWriteBuffer :: Device -> Buffer Word8 -> IO (Buffer Word8)

flushWriteBuffer :: Device -> Buffer Word8 -> IO (Buffer Word8)

flushWriteBuffer0 :: Device -> Buffer Word8 -> IO (Int, Buffer Word8)

IODevice Device

Defined in Data.Knob

Methods

ready :: Device -> Bool -> Int -> IO Bool

close :: Device -> IO ()

isTerminal :: Device -> IO Bool

isSeekable :: Device -> IO Bool

seek :: Device -> SeekMode -> Integer -> IO Integer

tell :: Device -> IO Integer

getSize :: Device -> IO Integer

setSize :: Device -> Integer -> IO ()

setEcho :: Device -> Bool -> IO ()

getEcho :: Device -> IO Bool

setRaw :: Device -> Bool -> IO ()

devType :: Device -> IO IODeviceType

dup :: Device -> IO Device

dup2 :: Device -> Device -> IO Device

RawIO Device

Defined in Data.Knob

Methods

read :: Device -> Ptr Word8 -> Word64 -> Int -> IO Int

readNonBlocking :: Device -> Ptr Word8 -> Word64 -> Int -> IO (Maybe Int)

write :: Device -> Ptr Word8 -> Word64 -> Int -> IO ()

writeNonBlocking :: Device -> Ptr Word8 -> Word64 -> Int -> IO Int

newDevice :: MonadIO m => Knob -> IOMode -> m Device