Cabal/Distribution/Lex.hs

   1 -----------------------------------------------------------------------------
   2 -- |
   3 -- Module      :  Distribution.Lex
   4 -- Copyright   :  Ben Gamari 2015-2019
   5 --
   6 -- Maintainer  :  cabal-devel@haskell.org
   7 -- Portability :  portable
   8 --
   9 -- This module contains a simple lexer supporting quoted strings
  10
  11 module Distribution.Lex (
  12         tokenizeQuotedWords
  13  ) where
  14
  15 import Prelude ()
  16 import Distribution.Compat.Prelude
  17 import Distribution.Compat.DList
  18
  19 tokenizeQuotedWords :: String -> [String]
  20 tokenizeQuotedWords = filter (not . null) . go False mempty
  21   where
  22     go :: Bool        -- ^ in quoted region
  23        -> DList Char  -- ^ accumulator
  24        -> String      -- ^ string to be parsed
  25        -> [String]    -- ^ parse result
  26     go _ accum []
  27       | [] <- accum' = []
  28       | otherwise    = [accum']
  29       where accum' = runDList accum
  30
  31     go False  accum (c:cs)
  32       | isSpace c = runDList accum : go False mempty cs
  33       | c == '"'  = go True accum cs
  34
  35     go True   accum (c:cs)
  36       | c == '"'  = go False accum cs
  37
  38     go quoted accum (c:cs)
  39                   = go quoted (accum `mappend` singleton c) cs
  40