Some optimisations to string splitting code.

Turns out that Data.List.Utils.split is slow and makes a lot of
allocations. Here's a much simpler single character splitter that behaves
the same (even in wacky corner cases) while running in half the time and
75% the allocations.

As well as being an optimisation, this helps move toward eliminating use of
missingh.

(Data.List.Split.splitOn is nearly as slow as Data.List.Utils.split and
allocates even more.)

I have not benchmarked the effect on git-annex, but would not be surprised
to see some parsing of eg, large streams from git commands run twice as
fast, and possibly in less memory.

This commit was sponsored by Boyd Stephen Smith Jr. on Patreon.

3 files changed, 3 insertions, 3 deletions

diff --git a/Remote/BitTorrent.hs b/Remote/BitTorrent.hs
index 0ec78aa64..2f29f5baa 100644
--- a/Remote/BitTorrent.hs
+++ b/Remote/BitTorrent.hs
@@ -302,7 +302,7 @@ ariaProgress (Just sz) meter ps = do
 		=<< ariaParams ps
 
 parseAriaProgress :: Integer -> ProgressParser
-parseAriaProgress totalsize = go [] . reverse . split ['\r']
+parseAriaProgress totalsize = go [] . reverse . splitc '\r'
   where
 	go remainder [] = (Nothing, remainder)
 	go remainder (x:xs) = case readish (findpercent x) of
diff --git a/Remote/Bup.hs b/Remote/Bup.hs
index 332e8d5dc..75b379558 100644
--- a/Remote/Bup.hs
+++ b/Remote/Bup.hs
@@ -254,7 +254,7 @@ bup2GitRemote r
 			else giveup "please specify an absolute path"
 	| otherwise = Git.Construct.fromUrl $ "ssh://" ++ host ++ slash dir
   where
-	bits = split ":" r
+	bits = splitc ':' r
 	host = Prelude.head bits
 	dir = intercalate ":" $ drop 1 bits
 	-- "host:~user/dir" is not supported specially by bup;
diff --git a/Remote/Helper/Encryptable.hs b/Remote/Helper/Encryptable.hs
index 45ceae068..029ac4b09 100644
--- a/Remote/Helper/Encryptable.hs
+++ b/Remote/Helper/Encryptable.hs
@@ -165,7 +165,7 @@ extractCipher c = case (M.lookup "cipher" c,
 		Just $ SharedCipher (fromB64bs t)
 	_ -> Nothing
   where
-	readkeys = KeyIds . split ","
+	readkeys = KeyIds . splitc ','
 
 describeEncryption :: RemoteConfig -> String
 describeEncryption c = case extractCipher c of