base-4.10.1.0: Basic libraries

Copyright | (c) The University of Glasgow 1994-2008
License | see libraries/base/LICENSE
Maintainer | libraries@haskell.org
Stability | internal
Portability | non-portable
Safe Haskell | Trustworthy
Language | Haskell2010

GHC.IO.Device

Description

Type classes for I/O providers.

Synopsis

- class RawIO a where
- class IODevice a where
- data IODeviceType
  - = Directory
  - | Stream
  - | RegularFile
  - | RawDevice
- data SeekMode
  - = AbsoluteSeek
  - | RelativeSeek
  - | SeekFromEnd

# Documentation

class RawIO a where #

A low-level I/O provider where the data is bytes in memory.

Minimal complete definition

read, readNonBlocking, write, writeNonBlocking

Methods

read :: a -> Ptr Word8 -> Int -> IO Int #

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) #

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 () #

Write the specified number of bytes.

writeNonBlocking :: a -> Ptr Word8 -> Int -> IO Int #

Write up to the specified number of bytes without blocking. Returns the actual number of bytes written.

class IODevice a where #

I/O operations required for implementing a `Handle`.

Minimal complete definition

ready, close, devType

Methods

ready :: a -> Bool -> Int -> IO Bool #

`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 () #

closes the device. Further operations on the device should produce exceptions.

isTerminal :: a -> IO Bool #

returns `True` if the device is a terminal or console.

isSeekable :: a -> IO Bool #

returns `True` if the device supports `seek` operations.

seek :: a -> SeekMode -> Integer -> IO () #

seek to the specified position in the data.

tell :: a -> IO Integer #

return the current position in the data.

getSize :: a -> IO Integer #

return the size of the data.

setSize :: a -> Integer -> IO () #

change the size of the data.

setEcho :: a -> Bool -> IO () #

for terminal devices, changes whether characters are echoed on the device.

getEcho :: a -> IO Bool #

returns the current echoing status.

setRaw :: a -> Bool -> IO () #

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 #

returns the `IODeviceType` corresponding to this device.

dup :: a -> IO a #

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 #

`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`).

data IODeviceType #

Type of a device that can be used to back a `Handle` (see also `mkFileHandle`). The standard libraries provide creation of `Handle`s via Posix file operations with file descriptors (see `mkHandleFromFD`) with FD being the underlying `IODevice` instance.

Users may provide custom instances of `IODevice` which are expected to conform the following rules:

Constructors

Directory | The standard libraries do not have direct support for this device type, but a user implementation is expected to provide a list of file names in the directory, in any order, separated by `'\0'` characters, excluding the `"."` and `".."` names. See also `getDirectoryContents`. Seek operations are not supported on directories (other than to the zero position).
Stream | A duplex communications channel (results in creation of a duplex `Handle`). The standard libraries use this device type when creating `Handle`s for open sockets.
RegularFile | A file that may be read or written, and also may be seekable.
RawDevice | A "raw" (disk) device which supports block binary read and write operations and may be seekable only to positions of certain granularity (block- aligned).

Instances

Eq IODeviceType # |
Methods (==) :: IODeviceType -> IODeviceType -> Bool Source # (/=) :: IODeviceType -> IODeviceType -> Bool Source #

data SeekMode #

A mode that determines the effect of `hSeek` `hdl mode i`.

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 # |
Methods succ :: SeekMode -> SeekMode # pred :: SeekMode -> SeekMode # toEnum :: Int -> SeekMode # fromEnum :: SeekMode -> Int # enumFrom :: SeekMode -> [SeekMode] # enumFromThen :: SeekMode -> SeekMode -> [SeekMode] # enumFromTo :: SeekMode -> SeekMode -> [SeekMode] # enumFromThenTo :: SeekMode -> SeekMode -> SeekMode -> [SeekMode] #
Eq SeekMode # |
Methods (==) :: SeekMode -> SeekMode -> Bool Source # (/=) :: SeekMode -> SeekMode -> Bool Source #
Ord SeekMode # |
Methods compare :: SeekMode -> SeekMode -> Ordering Source # (<) :: SeekMode -> SeekMode -> Bool Source # (<=) :: SeekMode -> SeekMode -> Bool Source # (>) :: SeekMode -> SeekMode -> Bool Source # (>=) :: SeekMode -> SeekMode -> Bool Source # max :: SeekMode -> SeekMode -> SeekMode Source # min :: SeekMode -> SeekMode -> SeekMode Source #
Read SeekMode # |
Methods readsPrec :: Int -> ReadS SeekMode # readList :: ReadS [SeekMode] # readPrec :: ReadPrec SeekMode # readListPrec :: ReadPrec [SeekMode] #
Show SeekMode # |
Methods showsPrec :: Int -> SeekMode -> ShowS # show :: SeekMode -> String # showList :: [SeekMode] -> ShowS #
Ix SeekMode # |
Methods range :: (SeekMode, SeekMode) -> [SeekMode] # index :: (SeekMode, SeekMode) -> SeekMode -> Int # unsafeIndex :: (SeekMode, SeekMode) -> SeekMode -> Int inRange :: (SeekMode, SeekMode) -> SeekMode -> Bool # rangeSize :: (SeekMode, SeekMode) -> Int # unsafeRangeSize :: (SeekMode, SeekMode) -> Int