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--------------------------------------------------------------------------------
--
-- Program : Preprocess
-- Copyright : (c) Sven Panne 2003
-- License : BSD-style (see the file libraries/OpenGL/LICENSE)
--
-- Maintainer : sven_panne@yahoo.com
-- Stability : provisional
-- Portability : portable
--
-- The .spec files from the SI are normally processed by Perl/AWK scripts and
-- have therefore a rather ugly line-oriented syntax. To make things more
-- amenable to "real" parsing, some lexical preprocessing is useful. Note that
-- the following algorithm doesn't remove or insert lines, which is important
-- for good error messages later. After this preprocessing, whitespace is not
-- significant anymore, apart from its common use as a token separator.
--
-- For every line do:
--
-- 1) Remove comments: Remove everything starting at the first '#'.
--
-- 2) Ignore passthru-hack: Consider lines starting with 'passthru:' as empty.
--
-- 3) Remove trailing whitespace.
--
-- 4) Mangle property declarations: Append ';' to a line where the first ':'
-- is only preceded by non-TAB and non-SPC characters. Additionally, move
-- that ':' to the beginning of the line.
--
-- 5) Separate definitions: Append ',' to a line starting with TAB and
-- followed (ignoring empty lines) by a line starting with TAB.
--
-- 6) Terminate definitions: Append ';' to a line starting with TAB and not
-- followed (ignoring empty lines) by a line starting with TAB.
--
--------------------------------------------------------------------------------
module Main ( main ) where
import Control.Monad ( liftM )
import Data.Char ( isSpace )
import Data.List ( isPrefixOf, tails )
import System.Environment ( getArgs )
--------------------------------------------------------------------------------
-- Preprocessing of spec files, making it more amenable to "real" parsing
--------------------------------------------------------------------------------
preprocess :: String -> String
preprocess = unlines .
addSeparators . mangleColonLines .
removeTrailingWhitespace . removePassthru . removeComments .
lines
where removeComments = map $ takeWhile (/= '#')
removePassthru = map $ \l -> if "passthru:" `isPrefixOf` l then "" else l
removeTrailingWhitespace = map $ reverse . dropWhile isSpace . reverse
mangleColonLines = map $ \l ->
case break (== ':') l of
(xs, ':':ys) | noSpaceIn xs -> ":" ++ xs ++ " " ++ ys ++ ";"
_ -> l
noSpaceIn = not . any (`elem` ['\t',' '])
addSeparators = map addSeparator . tails
addSeparator [] = []
addSeparator xs@(l:ls) | startsWithTabbedLine xs = l ++ separatorFor ls
| otherwise = l
separatorFor ls | startsWithTabbedLine (dropEmpty ls) = ","
| otherwise = ";"
dropEmpty = dropWhile ((== 0) . length)
startsWithTabbedLine (('\t':_):_) = True
startsWithTabbedLine _ = False
--------------------------------------------------------------------------------
-- The driver
--------------------------------------------------------------------------------
-- behave like 'cat'
mainWithArgs :: [String] -> IO ()
mainWithArgs fileNames = putStr . preprocess =<< input
where input | null fileNames = getContents
| otherwise = liftM concat (mapM readFile fileNames)
main :: IO ()
main = getArgs >>= mainWithArgs
|
