From 1f86b496ea8bcead95fddffe5b298384260155e5 Mon Sep 17 00:00:00 2001 From: Simon Marlow Date: Wed, 15 Sep 2010 13:13:41 +0000 Subject: [PATCH] documentation for IODeviceType (#4317, edited by me) --- GHC/IO/Device.hs | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/GHC/IO/Device.hs b/GHC/IO/Device.hs index ec1bde8..d1a6712 100644 --- a/GHC/IO/Device.hs +++ b/GHC/IO/Device.hs @@ -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) -- ----------------------------------------------------------------------------- -- 1.7.10.4