Allow construction of hashes using their underlying representation

Data/Digest/Murmur32.hs

@@ -13,7 +13,7 @@ MurmurHash2 algorithm. See <http://murmurhash.googlepages.com> for
 details on MurmurHash2.
 -}
 module Data.Digest.Murmur32
- ( Hash32, asWord32,
+ ( Hash32, asWord32, asHash32,
  Hashable32(..),
  hash32AddWord32, hash32AddInt, hash32, hash32WithSeed
  )
@@ -39,6 +39,10 @@ instance Show Hash32 where
 asWord32 :: Hash32 -> Word32
 asWord32 (Hash32 w) = w
 
+-- | Coerce a 32 bit word into a hash. This does not hash the input.
+asHash32 :: Word32 -> Hash32
+asHash32 = Hash32
+
 class Hashable32 a where
  hash32Add :: a -> Hash32 -> Hash32
 

Data/Digest/Murmur64.hs

@@ -13,7 +13,7 @@ MurmurHash2 algorithm. See <http://murmurhash.googlepages.com> for
 details on MurmurHash2.
 -}
 module Data.Digest.Murmur64
- ( Hash64, asWord64,
+ ( Hash64, asWord64, asHash64,
  Hashable64(..),
  hash64AddWord64, hash64AddInt, hash64, hash64WithSeed, combine,
  )
@@ -39,6 +39,10 @@ instance Show Hash64 where
 asWord64 :: Hash64 -> Word64
 asWord64 (Hash64 w) = w
 
+-- | Coerce a 64 bit word into a hash. This does not hash the input.
+asHash64 :: Word64 -> Hash64
+asHash64 = Hash64
+
 class Hashable64 a where
  hash64Add :: a -> Hash64 -> Hash64
 

changelog.md

@@ -1,3 +1,8 @@
+### Unreleased
+
+ - Introduce `asHash64` and `asHash32` which allow construction of `Hash64`
+ and `Hash32` respectively from their underlying word representation.
+
 ### 0.1.0.10
 
  - Replace use of deprecated `bitSize` by `finiteBitSize`