base-4.2.0.1: Basic libraries Source code Contents Index

GHC.IO.Device Portability non-portable Stability internal Maintainer libraries@haskell.org

Description

Type classes for I/O providers.

Synopsis

class RawIO a where read :: a -> Ptr Word8 -> Int -> IO Int readNonBlocking :: a -> Ptr Word8 -> Int -> IO (Maybe Int) write :: a -> Ptr Word8 -> Int -> IO () writeNonBlocking :: a -> Ptr Word8 -> Int -> IO Int class IODevice a where ready :: a -> Bool -> Int -> IO Bool close :: a -> IO () isTerminal :: a -> IO Bool isSeekable :: a -> IO Bool seek :: a -> SeekMode -> Integer -> IO () tell :: a -> IO Integer getSize :: a -> IO Integer setSize :: a -> Integer -> IO () setEcho :: a -> Bool -> IO () getEcho :: a -> IO Bool setRaw :: a -> Bool -> IO () devType :: a -> IO IODeviceType dup :: a -> IO a dup2 :: a -> a -> IO a data IODeviceType = Directory | Stream | RegularFile | RawDevice data SeekMode = AbsoluteSeek | RelativeSeek | SeekFromEnd

Documentation

class RawIO a where Source

A low-level I/O provider where the data is bytes in memory. Methods read :: a -> Ptr Word8 -> Int -> IO Int Source Read up to the specified number of bytes, returning the number of bytes actually read. This function should only block if there is no data available. If there is not enough data available, then the function should just return the available data. A return value of zero indicates that the end of the data stream (e.g. end of file) has been reached. readNonBlocking :: a -> Ptr Word8 -> Int -> IO (Maybe Int) Source Read up to the specified number of bytes, returning the number of bytes actually read, or Nothing if the end of the stream has been reached. write :: a -> Ptr Word8 -> Int -> IO () Source Write the specified number of bytes. writeNonBlocking :: a -> Ptr Word8 -> Int -> IO Int Source Write up to the specified number of bytes without blocking. Returns the actual number of bytes written. Instances RawIO FD

class IODevice a where Source

I/O operations required for implementing a Handle. Methods ready :: a -> Bool -> Int -> IO Bool Source ready dev write msecs returns True if the device has data to read (if write is False) or space to write new data (if write is True). msecs specifies how long to wait, in milliseconds. close :: a -> IO () Source closes the device. Further operations on the device should produce exceptions. isTerminal :: a -> IO Bool Source returns True if the device is a terminal or console. isSeekable :: a -> IO Bool Source returns True if the device supports seek operations. seek :: a -> SeekMode -> Integer -> IO () Source seek to the specified position in the data. tell :: a -> IO Integer Source return the current position in the data. getSize :: a -> IO Integer Source return the size of the data. setSize :: a -> Integer -> IO () Source change the size of the data. setEcho :: a -> Bool -> IO () Source for terminal devices, changes whether characters are echoed on the device. getEcho :: a -> IO Bool Source returns the current echoing status. setRaw :: a -> Bool -> IO () Source some devices (e.g. terminals) support a raw mode where characters entered are immediately made available to the program. If available, this operations enables raw mode. devType :: a -> IO IODeviceType Source returns the IODeviceType corresponding to this device. dup :: a -> IO a Source duplicates the device, if possible. The new device is expected to share a file pointer with the original device (like Unix dup). dup2 :: a -> a -> IO a Source dup2 source target replaces the target device with the source device. The target device is closed first, if necessary, and then it is made into a duplicate of the first device (like Unix dup2). Instances IODevice FD

data IODeviceType Source

Constructors Directory Stream RegularFile RawDevice Instances Eq IODeviceType

data SeekMode Source

A mode that determines the effect of hSeek hdl mode i, as follows: Constructors AbsoluteSeek the position of hdl is set to i. RelativeSeek the position of hdl is set to offset i from the current position. SeekFromEnd the position of hdl is set to offset i from the end of the file. Instances Enum SeekMode Eq SeekMode Ord SeekMode Read SeekMode Show SeekMode Ix SeekMode

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