Commit 13393fcd authored by Simon Marlow's avatar Simon Marlow
Browse files

documentation for IODeviceType (#4317, edited by me)

parent 880046fb
......@@ -132,11 +132,36 @@ class IODevice a where
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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