Added MD5 and MD5E backends.

Backend/Hash.hs

@@ -5,8 +5,6 @@
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
-{-# LANGUAGE CPP #-}
-
 module Backend.Hash (
 	backends,
 	testKeyBackend,
@@ -24,7 +22,7 @@ import qualified Build.SysConfig as SysConfig
 import qualified Data.ByteString.Lazy as L
 import Data.Char
 
-data Hash = SHAHash HashSize | SkeinHash HashSize
+data Hash = SHAHash HashSize | SkeinHash HashSize | MD5Hash
 type HashSize = Int
 
 {- Order is slightly significant; want SHA256 first, and more general
@@ -33,6 +31,7 @@ hashes :: [Hash]
 hashes = concat 
 	[ map SHAHash [256, 1, 512, 224, 384]
 	, map SkeinHash [256, 512]
+	, [MD5Hash]
 	]
 
 {- The SHA256E backend is the default, so genBackendE comes first. -}
@@ -58,6 +57,7 @@ genBackendE hash = (genBackend hash)
 hashName :: Hash -> String
 hashName (SHAHash size) = "SHA" ++ show size
 hashName (SkeinHash size) = "SKEIN" ++ show size
+hashName MD5Hash = "MD5"
 
 hashNameE :: Hash -> String
 hashNameE hash = hashName hash ++ "E"
@@ -154,6 +154,7 @@ hashFile hash file filesize = liftIO $ go hash
 			either error return 
 				=<< externalSHA command hashsize file
 	go (SkeinHash hashsize) = skeinHasher hashsize <$> L.readFile file
+	go MD5Hash = md5Hasher <$> L.readFile file
 
 shaHasher :: HashSize -> Integer -> Either (L.ByteString -> String) String
 shaHasher hashsize filesize
@@ -180,6 +181,9 @@ skeinHasher hashsize
 	| hashsize == 512 = show . skein512
 	| otherwise = error $ "unsupported skein size " ++ show hashsize
 
+md5Hasher :: L.ByteString -> String
+md5Hasher = show . md5
+
 {- A varient of the SHA256E backend, for testing that needs special keys
  - that cannot collide with legitimate keys in the repository.
  -

Utility/Hash.hs

@@ -8,6 +8,7 @@ module Utility.Hash (
 	sha512,
 	skein256,
 	skein512,
+	md5,
 	prop_hashes_stable
 ) where
 
@@ -42,6 +43,9 @@ skein256 = hashlazy
 skein512 :: L.ByteString -> Digest Skein512_512
 skein512 = hashlazy
 
+md5 ::  L.ByteString -> Digest MD5
+md5 = hashlazy
+
 {- Check that all the hashes continue to hash the same. -}
 prop_hashes_stable :: Bool
 prop_hashes_stable = all (\(hasher, result) -> hasher foo == result)
@@ -52,6 +56,7 @@ prop_hashes_stable = all (\(hasher, result) -> hasher foo == result)
 	, (show . sha512, "f7fbba6e0636f890e56fbbf3283e524c6fa3204ae298382d624741d0dc6638326e282c41be5e4254d8820772c5518a2c5a8c0c7f7eda19594a7eb539453e1ed7")
 	, (show . skein256, "a04efd9a0aeed6ede40fe5ce0d9361ae7b7d88b524aa19917b9315f1ecf00d33")
 	, (show . skein512, "fd8956898113510180aa4658e6c0ac85bd74fb47f4a4ba264a6b705d7a8e8526756e75aecda12cff4f1aca1a4c2830fbf57f458012a66b2b15a3dd7d251690a7")
+	, (show . md5, "acbd18db4cc2f85cedef654fccc4a4d8")
 	]
   where
 	foo = L.fromChunks [T.encodeUtf8 $ T.pack "foo"]

debian/changelog

@@ -29,6 +29,7 @@ git-annex (5.20150114) UNRELEASED; urgency=medium
   * Support annex.tune.objecthash1, annex.tune.objecthashlower, and
     annex.tune.branchhash1.
   * Remove support for building without cryptohash.
+  * Added MD5 and MD5E backends.
 
  -- Joey Hess <id@joeyh.name>  Tue, 13 Jan 2015 17:03:39 -0400
 

doc/backends.mdwn

@@ -17,8 +17,8 @@ can use different ones for different files.
   This is the least expensive backend, recommended for really large
   files or slow systems.
 * `SHA512`, `SHA512E` -- Best SHA-2 hash, for the very paranoid.
-* `SHA1`, `SHA1E` -- Smaller hash than `SHA256` for those who want a checksum
+* `SHA1`, `SHA1E`, `MD5`, `MD5E` -- Smaller hashes than `SHA256`
-   but are not concerned about security.
+   for those who want a checksum but are not concerned about security.
 * `SHA384`, `SHA384E`, `SHA224`, `SHA224E` -- Hashes for people who like
   unusual sizes.
 * `SKEIN512`, `SKEIN512E`, `SKEIN256`, `SKEIN256E`