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44 lines
1.4 KiB
44 lines
1.4 KiB
module HashTrees where
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import Data.Digest.Pure.SHA
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import qualified Data.ByteString.Lazy as BL
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import Control.Monad
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import Data.List
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data HashTree k a = Leaf | HashTree (Digest k) (HashTree k a) (HashTree k a) deriving (Show)
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groupsOf _ ([]) = []
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groupsOf n xs = case splitAt n xs of
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(a, as) -> a : (groupsOf n as)
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groupsOf2 xs = map (\(x:y:[]) -> (x,y)) $ groupsOf 2 xs
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hashCatInner (h1, h2) = sha1 $ BL.concat [(bytestringDigest h1), (bytestringDigest h2), BL.singleton 1]
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hashes = map sha1
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singletonTrees xs = map (\x -> HashTree x Leaf Leaf) xs
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reduceHashes xs = map (\((HashTree x _ _), (HashTree y _ _)) -> HashTree (hashCatInner (x,y)) Leaf Leaf) (groupsOf2 xs)
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combineTrees (HashTree x _ _) (t1, t2) = HashTree x t1 t2
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combineTreeLists lower upper = zipWith combineTrees upper (groupsOf2 lower)
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buildPreliminaryLevels ([x]) = [[x]]
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buildPreliminaryLevels xs = xs : (buildPreliminaryLevels $ (reduceHashes xs))
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buildTree' :: [HashTree k t] -> [[HashTree k t]] -> [HashTree k t]
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buildTree' acc ([]) = acc
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buildTree' acc (x:xs) = buildTree' (combineTreeLists acc x) xs
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buildTree = (\x -> buildTree' (head x) (tail x)) . buildPreliminaryLevels . singletonTrees . hashes . (map (\x -> BL.concat [x,BL.singleton 0])) . padHashes
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-- Padding functions
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nextPowerOf n = 2 ^ (ceiling $ logBase 2 $ fromIntegral n)
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padHashes xs = pad' 0 xs where
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pad' n ([]) = [] ++ (take ((nextPowerOf n) - n) $ repeat BL.empty)
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pad' n (x:xs) = x : (pad' (n +1) xs)
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