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+-- |
+-- Module:      CGroup
+-- Copyright:   (c) 2014 Tomislav Viljetić
+-- License:     BSD3
+-- Maintainer:  Tomislav Viljetić <tomislav@viljetic.de>
+--
+-- Basic cgroup virtual filesystem operations.
+--
+
+module CGroup
+    ( module CGroup.Types
+    , createCGroup
+    , classifyTask
+    , listTasks
+    ) where
+
+import CGroup.Types
+import Control.Applicative
+import Data.Attoparsec.ByteString.Char8
+import Data.Set (Set)
+import qualified Data.Set as Set
+import System.Directory (createDirectory)
+import System.FilePath ((</>))
+import System.IO.Streams.Attoparsec (parseFromStream)
+import System.IO.Streams.File (withFileAsInput)
+
+
+-- | @'createCGroup' g@ creates a new cgroup @g@.
+createCGroup :: CGroup -> IO ()
+createCGroup =
+    createDirectory . cgroupPath
+
+
+-- | @'classifyTask' g pid@ places task @pid@ into cgroup @g@.
+classifyTask :: ProcessID -> CGroup -> IO ()
+classifyTask pid g =
+    writeFile (tasksFile g) (show pid)
+
+
+-- | @'listTasks' g@ returns tasks of cgroup @g@.
+listTasks :: CGroup -> IO (Set ProcessID)
+listTasks g =
+    withFileAsInput (tasksFile g) $ parseFromStream tasksParser
+
+
+tasksFile :: CGroup -> FilePath
+tasksFile =
+    (</> "tasks") . cgroupPath
+
+
+tasksParser :: Parser (Set ProcessID)
+tasksParser =
+    Set.fromList <$> many' (decimal <* endOfLine) <* endOfInput <?> "tasks"