src/Ganeti/Cpu/LoadParser.hs

{-# LANGUAGE OverloadedStrings #-}
{-| /proc/stat file parser

This module holds the definition of the parser that extracts information
about the CPU load of the system from the @/proc/stat@ file.

-}
{-

Copyright (C) 2013 Google Inc.
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2. Redistributions in binary form must reproduce the above copyright
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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-}
module Ganeti.Cpu.LoadParser (cpustatParser) where

import Prelude ()
import Ganeti.Prelude

import Control.Applicative ((<|>))
import qualified Data.Attoparsec.Text as A
import qualified Data.Attoparsec.Combinator as AC
import Data.Attoparsec.Text (Parser)

import Ganeti.Parsers
import Ganeti.Cpu.Types

-- * Parser implementation

-- | The parser for one line of the CPU status file.
oneCPUstatParser :: Parser CPUstat
oneCPUstatParser =
  let nameP = stringP
      userP = integerP
      niceP = integerP
      systemP = integerP
      idleP = integerP
      iowaitP = integerP
      irqP = integerP
      softirqP = integerP
      stealP = integerP
      guestP = integerP
      guest_niceP = integerP
  in
    CPUstat <$> nameP <*> userP <*> niceP <*> systemP <*> idleP <*> iowaitP
            <*> irqP <*> softirqP <*> stealP <*> guestP <*> guest_niceP
            <* A.endOfLine

-- | When this is satisfied all the lines containing information about
-- the CPU load are parsed.
intrFound :: Parser ()
intrFound = (A.string "intr" *> return ())
             <|> (A.string "page" *> return ())
             <|> (A.string "swap" *> return ())

-- | The parser for the fragment of CPU status file containing
-- information about the CPU load.
cpustatParser :: Parser [CPUstat]
cpustatParser = oneCPUstatParser `AC.manyTill` intrFound