| 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.
- class RawIO a where
- class IODevice a where
- data IODeviceType
- data SeekMode
Documentation
A low-level I/O provider where the data is bytes in memory.
Minimal complete definition
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.
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.
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 #
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 :: 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).
data IODeviceType Source #
Type of a device that can be used to back a
Handle (see also mkFileHandle). The
standard libraries provide creation of Handles 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 |
| 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). |
Instances
A mode that determines the effect of hSeek hdl mode i.
Constructors
| AbsoluteSeek | the position of |
| RelativeSeek | the position of |
| SeekFromEnd | the position of |