Serialise Texts without going through ByteString

src/Data/Text.hs

@@ -235,6 +235,7 @@ import qualified Data.Text.Array as A
 import qualified Data.List as L hiding (head, tail)
 import qualified Data.List.NonEmpty as NonEmptyList
 import Data.Binary (Binary(get, put))
+import Data.Binary.Put (putBuilder)
 import Data.Monoid (Monoid(..))
 import Data.Semigroup (Semigroup(..))
 import Data.String (IsString(..))
@@ -245,7 +246,7 @@ import Data.Text.Internal.Measure (measure_off)
 import Data.Text.Internal.Encoding.Utf8 (utf8Length, utf8LengthByLeader, chr3, ord2, ord3, ord4)
 import qualified Data.Text.Internal.Fusion as S
 import qualified Data.Text.Internal.Fusion.Common as S
-import Data.Text.Encoding (decodeUtf8', encodeUtf8)
+import Data.Text.Encoding (decodeUtf8', encodeUtf8Builder)
 import Data.Text.Internal.Fusion (stream, reverseStream, unstream)
 import Data.Text.Internal.Private (span_)
 import Data.Text.Internal (Text(..), StrictText, empty, firstf, mul, safe, text, append, pack)
@@ -394,7 +395,11 @@ instance NFData Text where rnf !_ = ()
 
 -- | @since 1.2.1.0
 instance Binary Text where
-    put t = put (encodeUtf8 t)
+    put t = do
+      -- This needs to be in sync with the Binary instance for ByteString
+      -- in the binary package.
+      put (lengthWord8 t)
+      putBuilder (encodeUtf8Builder t)
     get   = do
       bs <- get
       case decodeUtf8' bs of
@@ -556,7 +561,7 @@ null (Text _arr _off len) =
     len <= 0
 {-# INLINE [1] null #-}
 
-{-# RULES 
+{-# RULES
  "TEXT null/empty -> True" null empty = True
 #-}
 
@@ -1277,7 +1282,7 @@ take :: Int -> Text -> Text
 take n t@(Text arr off len)
     | n <= 0    = empty
     | n >= len || m >= len || m < 0  = t
-    | otherwise = Text arr off m 
+    | otherwise = Text arr off m
   where
     m = measureOff n t
 {-# INLINE [1] take #-}
@@ -1327,7 +1332,7 @@ drop :: Int -> Text -> Text
 drop n t@(Text arr off len)
     | n <= 0    = t
     | n >= len || m >= len || m < 0 = empty
-    | otherwise = Text arr (off+m) (len-m) 
+    | otherwise = Text arr (off+m) (len-m)
   where m = measureOff n t
 {-# INLINE [1] drop #-}
 
@@ -1436,7 +1441,7 @@ splitAt :: Int -> Text -> (Text, Text)
 splitAt n t@(Text arr off len)
     | n <= 0    = (empty, t)
     | n >= len || m >= len || m < 0  = (t, empty)
-    | otherwise = (Text arr off m, Text arr (off+m) (len-m)) 
+    | otherwise = (Text arr off m, Text arr (off+m) (len-m))
   where
     m = measureOff n t
 

src/Data/Text/Lazy.hs

@@ -223,6 +223,7 @@ import Data.Char (isSpace)
 import Data.Data (Data(gfoldl, toConstr, gunfold, dataTypeOf), constrIndex,
                   Constr, mkConstr, DataType, mkDataType, Fixity(Prefix))
 import Data.Binary (Binary(get, put))
+import Data.Binary.Put (putBuilder)
 import Data.List.NonEmpty (NonEmpty(..))
 import qualified Data.List.NonEmpty as NE
 import Data.Monoid (Monoid(..))
@@ -241,7 +242,7 @@ import Data.Text.Internal.Lazy (Text(..), chunk, empty, foldlChunks,
 import Data.Text.Internal (firstf, safe, text)
 import Data.Text.Internal.Reverse (reverseNonEmpty)
 import Data.Text.Internal.Transformation (mapNonEmpty, toCaseFoldNonEmpty, toLowerNonEmpty, toUpperNonEmpty, filter_)
-import Data.Text.Lazy.Encoding (decodeUtf8', encodeUtf8)
+import Data.Text.Lazy.Encoding (decodeUtf8', encodeUtf8Builder)
 import Data.Text.Internal.Lazy.Search (indices)
 import qualified GHC.CString as GHC
 import qualified GHC.Exts as Exts
@@ -352,7 +353,11 @@ instance NFData Text where
 
 -- | @since 1.2.1.0
 instance Binary Text where
-    put t = put (encodeUtf8 t)
+    put t = do
+      -- This needs to be in sync with the Binary instance for ByteString
+      -- in the binary package.
+      put (foldlChunks (\n c -> n + T.lengthWord8 c) 0 t)
+      putBuilder (encodeUtf8Builder t)
     get   = do
       bs <- get
       case decodeUtf8' bs of

tests/Tests/Properties/Instances.hs

@@ -6,6 +6,7 @@ module Tests.Properties.Instances
     ( testInstances
     ) where
 
+import Data.Binary (encode, decodeOrFail)
 import Data.String (IsString(fromString))
 import Test.QuickCheck
 import Test.Tasty (TestTree, testGroup)
@@ -43,6 +44,16 @@ tl_mempty         = mempty === (unpackS (mempty :: TL.Text))
 t_IsString        = fromString  `eqP` (T.unpack . fromString)
 tl_IsString       = fromString  `eqP` (TL.unpack . fromString)
 
+t_Binary s        =
+  case decodeOrFail . encode $ (s :: T.Text) of
+    Left _   -> counterexample (show (T.unpack s)) (property False)
+    Right (_, _, s') -> s === s'
+
+tl_Binary s       =
+  case decodeOrFail . encode $ (s :: TL.Text) of
+    Left _   -> counterexample (show (TL.unpack s)) (property False)
+    Right (_, _, s') -> s === s'
+
 testInstances :: TestTree
 testInstances =
   testGroup "instances" [
@@ -65,5 +76,7 @@ testInstances =
     testProperty "t_mempty" t_mempty,
     testProperty "tl_mempty" tl_mempty,
     testProperty "t_IsString" t_IsString,
-    testProperty "tl_IsString" tl_IsString
+    testProperty "tl_IsString" tl_IsString,
+    testProperty "t_Binary" t_Binary,
+    testProperty "tl_Binary" tl_Binary
   ]

text.cabal

@@ -294,6 +294,7 @@ test-suite tests
   build-depends:
     QuickCheck >= 2.12.6 && < 2.16,
     base <5,
+    binary,
     bytestring,
     deepseq,
     directory,