ioe_unsupportedOperation :: IO a
ioe_unsupportedOperation = throwIO unsupportedOperation
+-- | Type of a device that can be used to back a
+-- 'GHC.IO.Handle.Handle' (see also 'GHC.IO.Handle.mkFileHandle'). The
+-- standard libraries provide creation of 'GHC.IO.Handle.Handle's via
+-- Posix file operations with file descriptors (see
+-- 'GHC.IO.Handle.FD.mkHandleFromFD') with FD being the underlying
+-- 'GHC.IO.Device.IODevice' instance.
+--
+-- Users may provide custom instances of 'GHC.IO.Device.IODevice'
+-- which are expected to conform the following rules:
+
data IODeviceType
- = Directory
- | Stream
- | RegularFile
- | RawDevice
+ = Directory -- ^ The standard libraries do not have direct support
+ -- for this device type, but user implementation is
+ -- expected to provide a newline-separated list of
+ -- file names in a directory (without path to the
+ -- directory itself) in any order,
+ -- excluding the @"."@ and @".."@ names. See
+ -- also 'System.Directory.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 'GHC.IO.Handle.Handle'). The
+ -- standard libraries use this device type when
+ -- creating 'GHC.IO.Handle.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).
deriving (Eq)
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