base-4.2.0.0: Basic librariesContentsIndex
GHC.IO.Device
Portabilitynon-portable
Stabilityinternal
Maintainerlibraries@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
A low-level I/O provider where the data is bytes in memory.
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.
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
Constructors
Directory
Stream
RegularFile
RawDevice
data SeekMode
A mode that determines the effect of hSeek hdl mode i, as follows:
Constructors
AbsoluteSeekthe position of hdl is set to i.
RelativeSeekthe position of hdl is set to offset i from the current position.
SeekFromEndthe position of hdl is set to offset i from the end of the file.
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