1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
|
{-# LANGUAGE CPP, PatternGuards, ScopedTypeVariables #-}
module Main where
-- A time- and output-limited unlambda
#if !MIN_VERSION_base(4,6,0)
import Prelude hiding(catch)
#endif
import Control.Exception (catch, IOException)
import System.Posix.Resource
import Data.Char (toLower)
import System.IO (hGetChar, hGetLine, stdin, Handle())
import Language.Unlambda
{- WARNING: There is no way this is actually enough sandboxing (mueval has to do
a heck of a lot more to safely valuate expressions and not all of it
involves libraries), but since no one seems to be attacking via `unlambda`
we'll leave this be. -}
main :: IO Exp
main = (setResourceLimit ResourceCPUTime $ ResourceLimits (ResourceLimit 5) (ResourceLimit 5)) >> run
run :: IO Exp
run = do
expr <- parse stdin
let (Eval cp) = eval expr
cp (Nothing, 2048) (const return)
------------------------------------------------------------------------
-- Parsing of the Unlambda program directly from handle
--
parse :: Handle -> IO Exp
parse h = do
c <- catch (hGetChar h) (\(_ :: IOException) -> error "Parse error at end of file")
case toLower c of
d | d `elem` " \t\n" -> parse h
'`' -> do e1 <- parse h
e2 <- parse h
return (App e1 e2)
'#' -> hGetLine h >> parse h
'.' -> hGetChar h >>= return . Dot
'?' -> hGetChar h >>= return . Ques
_ | Just fn <- lookup c table -> return fn
| otherwise -> error $ "Unknown operator " ++ show c
where table = zip "ksivcdre@|" [K,S,I,V,C,D,Dot '\n',E,At,Pipe]
|
