Manually define sconcat to use the efficient concat function

Changelog.md

@@ -7,6 +7,7 @@
  * Fix GHC Travis CI 7.0 builds
  * Fix benchmark builds
  * Add GHC 8.10 to the CI matrix
+ * Improve the performance of `sconcat` for lazy and strict bytestrings
 
 0.10.10.0 July 2019 <duncan+haskell@dcoutts.me.uk> July 2019
 

Data/ByteString/Internal.hs

@@ -91,9 +91,14 @@ import Foreign.C.Types          (CInt, CSize, CULong)
 
 import Foreign.C.String         (CString)
 
-#if !(MIN_VERSION_base(4,11,0)) && MIN_VERSION_base(4,9,0)
-import Data.Semigroup           (Semigroup((<>)))
+#if MIN_VERSION_base(4,13,0)
+import Data.Semigroup           (Semigroup (sconcat))
+import Data.List.NonEmpty       (NonEmpty ((:|)))
+#elif MIN_VERSION_base(4,9,0)
+import Data.Semigroup           (Semigroup ((<>), sconcat))
+import Data.List.NonEmpty       (NonEmpty ((:|)))
 #endif
+
 #if !(MIN_VERSION_base(4,8,0))
 import Data.Monoid              (Monoid(..))
 #endif
@@ -156,6 +161,7 @@ instance Ord ByteString where
 #if MIN_VERSION_base(4,9,0)
 instance Semigroup ByteString where
     (<>)    = append
+    sconcat (b:|bs) = concat (b:bs)
 #endif
 
 instance Monoid ByteString where

Data/ByteString/Lazy/Internal.hs

@@ -51,8 +51,12 @@ import qualified Data.ByteString          as S (length, take, drop)
 import Data.Word        (Word8)
 import Foreign.Storable (Storable(sizeOf))
 
-#if !(MIN_VERSION_base(4,11,0)) && MIN_VERSION_base(4,9,0)
-import Data.Semigroup   (Semigroup((<>)))
+#if MIN_VERSION_base(4,13,0)
+import Data.Semigroup   (Semigroup (sconcat))
+import Data.List.NonEmpty (NonEmpty ((:|)))
+#elif MIN_VERSION_base(4,9,0)
+import Data.Semigroup   (Semigroup ((<>), sconcat))
+import Data.List.NonEmpty (NonEmpty ((:|)))
 #endif
 #if !(MIN_VERSION_base(4,8,0))
 import Data.Monoid      (Monoid(..))
@@ -84,6 +88,7 @@ instance Ord ByteString where
 #if MIN_VERSION_base(4,9,0)
 instance Semigroup ByteString where
     (<>)    = append
+    sconcat (b:|bs) = concat (b:bs)
 #endif
 
 instance Monoid ByteString where