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1+module Data.Hash
2+
3+%access public
4+%default total
5+
6+{- A general purpose Hashing library (not cryptographic)
7+
8+ The core hash is djb2, which is very fast but does not have the best distribution
9+ Source: http://www.cse.yorku.ca/~oz/hash.html
10+
11+ The salted version and the magic salt are copied from Haskell's bloomfilter library
12+ Source: https://hackage.haskell.org/package/bloomfilter-2.0.0.0/docs/src/Data-BloomFilter-Hash.html#Hashable
13+-}
14+
15+||| A type that can be hashed
16+class Hashable a where
17+ saltedHash64 : a -> Bits64 -> Bits64 -- value to hash, salt, hash
18+
19+||| Computes a non cryptographic hash
20+hash : Hashable a => a -> Bits64
21+hash x = saltedHash64 x 0x16fc397cf62f64d3
22+
23+||| Given a user provided salt, computes a non cryptographic hash.
24+||| This version is meant to mitigate hash-flooding DoS attacks.
25+saltedHash : Hashable a => Bits64 -> a -> Bits64
26+saltedHash salt x = saltedHash64 x salt
27+
28+
29+||| Nth byte of a Bits64
30+private
31+byte : Bits64 -> Bits64 -> Bits64
32+byte n w = prim__lshrB64 (prim__andB64 mask w) offset
33+ where offset = 8*n
34+ mask = prim__shlB64 0xff (the Bits64 offset)
35+
36+||| Modulo of an integer, downsized to a Bits64
37+private
38+mod64 : Integer -> Bits64
39+mod64 i = assert_total $ prim__truncBigInt_B64 (abs i `mod` 0xffffffffffffffff)
40+
41+instance Hashable Bits64 where
42+ saltedHash64 w salt = foldr (\b,acc => (acc `prim__shlB64` 10) + acc + b)
43+ salt
44+ [byte (fromInteger n) w | n <- [7,6..0]] -- djb2 hash function. Not meant for crypto
45+
46+instance Hashable Integer where
47+ saltedHash64 i = saltedHash64 (mod64 i)
48+
49+instance Hashable () where
50+ saltedHash64 _ salt = salt
51+
52+instance Hashable Bool where
53+ saltedHash64 True = saltedHash64 (the Bits64 1)
54+ saltedHash64 False = saltedHash64 (the Bits64 0)
55+
56+instance Hashable Int where
57+ saltedHash64 w = saltedHash64 (prim__zextInt_B64 w)
58+
59+instance Hashable Char where
60+ saltedHash64 w = saltedHash64 (the Int (cast w))
61+
62+instance Hashable Bits8 where
63+ saltedHash64 w = saltedHash64 (prim__zextB8_B64 w)
64+
65+instance Hashable Bits16 where
66+ saltedHash64 w = saltedHash64 (prim__zextB16_B64 w)
67+
68+instance Hashable Bits32 where
69+ saltedHash64 w = saltedHash64 (prim__zextB32_B64 w)
70+
71+instance Hashable a => Hashable (Maybe a) where
72+ saltedHash64 Nothing salt = salt
73+ saltedHash64 (Just k) salt = saltedHash64 k salt
74+
75+instance (Hashable a, Hashable b) => Hashable (a, b) where
76+ saltedHash64 (a,b) salt = saltedHash64 b (saltedHash64 a salt)
77+
78+instance Hashable a => Hashable (List a) where
79+ saltedHash64 l salt = foldr (\c,acc => saltedHash64 c acc) salt l
80+
81+instance Hashable a => Hashable (Vect n a) where
82+ saltedHash64 l salt = foldr (\c,acc => saltedHash64 c acc) salt l
83+
84+instance Hashable String where
85+ saltedHash64 s = saltedHash64 (unpack s)