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{-# LANGUAGE OverloadedStrings #-}

{-| Diskstats proc file parser

This module holds the definition of the parser that extracts status

information about the disks of the system from the @/proc/diskstats@ file.

-}

{-

Copyright (C) 2013 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.Storage.Diskstats.Parser (diskstatsParser) where

import Control.Applicative ((<*>), (*>), (<*), (<$>))

import qualified Data.Attoparsec.Text as A

import qualified Data.Attoparsec.Combinator as AC

import Data.Attoparsec.Text (Parser)

import Data.Text (unpack)

import Ganeti.Storage.Diskstats.Types

-- * Utility functions

-- | Our own space-skipping function, because A.skipSpace also skips

-- newline characters. It skips ZERO or more spaces, so it does not

-- fail if there are no spaces.

skipSpaces :: Parser ()

skipSpaces = A.skipWhile A.isHorizontalSpace

-- | A parser recognizing a number preceeded by spaces.

numberP :: Parser Int

numberP = skipSpaces *> A.decimal

-- | A parser recognizing a word preceded by spaces, and closed by a space.

stringP :: Parser String

stringP = skipSpaces *> fmap unpack (A.takeWhile $ not . A.isHorizontalSpace)

-- * Parser implementation

-- | The parser for one line of the diskstatus file.

oneDiskstatsParser :: Parser Diskstats

oneDiskstatsParser =

  Diskstats <$> numberP <*> numberP <*> stringP <*> numberP <*> numberP

    <*> numberP <*> numberP <*> numberP <*> numberP <*> numberP <*> numberP

    <*> numberP <*> numberP <*> numberP <* A.endOfLine

-- | The parser for a whole diskstatus file.

diskstatsParser :: Parser [Diskstats]

diskstatsParser = oneDiskstatsParser `AC.manyTill` A.endOfInput