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Watch out for overflows in BootString

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darcs-hash:20080120013020-a4fee-282b60f860817f1f5994e4a867980d02f8020609
This commit is contained in:
Henning Guenther 2008-01-19 17:30:20 -08:00
parent 8d740cf88a
commit 42cdeecc96
1 changed files with 12 additions and 8 deletions
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20
Data/Encoding/BootString.hs
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@ -62,7 +62,6 @@ getT bs k bias
| k >= bias + (tmax bs) = tmax bs
| otherwise = k-bias
adapt :: BootString -> Int -> Int -> Bool -> Int
adapt bs delta numpoints firsttime = let
delta1 = if firsttime
@ -75,24 +74,29 @@ adapt bs delta numpoints firsttime = let
in rk + (((base bs - tmin bs +1) * rd) `div` (rd + skew bs))
decodeValue :: BootString -> Int -> Int -> Int -> Int -> [Int] -> (Int,[Int])
decodeValue bs bias i k w (x:xs) = let
decodeValue bs bias i k w (x:xs)
| x >= base bs = throwDyn OutOfRange
| x > (maxBound - i) `div` w = throwDyn OutOfRange
| x < t = (ni,xs)
| w > maxBound `div` (base bs - t) = throwDyn OutOfRange
| otherwise = decodeValue bs bias ni (k+base bs) (w*(base bs - t)) xs
where
ni = i + x*w
t = getT bs k bias
in if x < t
then (ni,xs)
else decodeValue bs bias ni (k+base bs) (w*(base bs - t)) xs
decodeValues :: BootString -> Int -> [Int] -> [(Char,Int)]
decodeValues bs len xs = decodeValues' bs (init_n bs) 0 (init_bias bs) len xs
decodeValues' :: BootString -> Int -> Int -> Int -> Int -> [Int] -> [(Char,Int)]
decodeValues' bs n i bias len [] = []
decodeValues' bs n i bias len xs = let
decodeValues' bs n i bias len xs
| dn > maxBound - n = throwDyn OutOfRange
| otherwise = (chr $ nn,nni):decodeValues' bs nn (nni+1)
(adapt bs (ni-i) (len+1) (i==0)) (len+1) rst
where
(ni,rst) = decodeValue bs bias i (base bs) 1 xs
(dn,nni) = ni `divMod` (len+1)
nn = n + dn
in (chr $ nn,nni):decodeValues' bs nn (nni+1)
(adapt bs (ni-i) (len+1) (i==0)) (len+1) rst
insertDeltas :: [(Char,Int)] -> String -> String
insertDeltas [] str = str