Copyright | (c) The University of Glasgow 1994-2008 |
---|---|
License | see libraries/base/LICENSE |
Maintainer | [email protected] |
Stability | internal |
Portability | non-portable |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Type classes for I/O providers.
A low-level I/O provider where the data is bytes in memory.
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.
I/O operations required for implementing a Handle
.
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.
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.
duplicates the device, if possible. The new device is expected to share a file pointer with the original device (like Unix dup
).
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 Source
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:
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 |
Stream | A duplex communications channel (results in creation of a duplex |
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). |
A mode that determines the effect of hSeek
hdl mode i
.
AbsoluteSeek | the position of |
RelativeSeek | the position of |
SeekFromEnd | the position of |
© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/8.2.1/docs/html/libraries/base-4.10.0.0/GHC-IO-Device.html