WIP: experimentally use dupIO to fix #318

This calls dupIO on the token stream each time the buffer is full.

Author: adamgundry

cborg/cborg.cabal

@@ -94,6 +94,7 @@ library
     bytestring              >= 0.10.4  && < 0.12,
     containers              >= 0.5     && < 0.7,
     deepseq                 >= 1.0     && < 1.5,
+    dupIO,
     ghc-prim                >= 0.3.1.0 && < 0.11,
     half                    >= 0.2.2.3 && < 0.4,
     primitive               >= 0.5     && < 0.9,

cborg/src/Codec/CBOR/Write.hs

@@ -75,6 +75,8 @@ import qualified Codec.CBOR.ByteArray.Sliced           as BAS
 import           Codec.CBOR.Encoding
 import           Codec.CBOR.Magic
 
+import qualified Data.Dup                              as Dup
+
 --------------------------------------------------------------------------------
 
 -- | Turn an 'Encoding' into a lazy 'L.ByteString' in CBOR binary
@@ -194,7 +196,8 @@ buildStep vs1 k (BI.BufferRange op0 ope0) =
 
           TkEnd            -> k (BI.BufferRange op ope0)
 
-      | otherwise = return $ BI.bufferFull bound op (buildStep vs k)
+      | otherwise = do vs' <- Dup.dupIO vs
+                       return $ BI.bufferFull bound op (buildStep vs' k)
 
     -- The maximum size in bytes of the fixed-size encodings
     bound :: Int