Use ByteString rather than FastBytes inside FastZString

Slow nofib Compile Times difference looks like just noise:
-1 s.d.        -2.9%
+1 s.d.        +2.9%
Average        -0.1%

1 files changed, 20 insertions, 11 deletions

diff --git a/compiler/utils/BufWrite.hs b/compiler/utils/BufWrite.hs
index ea5cee01db..5ad165dcd8 100644
--- a/compiler/utils/BufWrite.hs
+++ b/compiler/utils/BufWrite.hs
@@ -35,8 +35,11 @@ import FastTypes
 import FastMutInt
 
 import Control.Monad	( when )
+import Data.ByteString (ByteString)
+import qualified Data.ByteString.Unsafe as BS
 import Data.Char	( ord )
 import Foreign
+import Foreign.C.String
 import System.IO
 
 -- -----------------------------------------------------------------------------
@@ -88,21 +91,27 @@ bPutFS :: BufHandle -> FastString -> IO ()
 bPutFS b fs = bPutFB b $ fastStringToFastBytes fs
 
 bPutFZS :: BufHandle -> FastZString -> IO ()
-bPutFZS b fs = bPutFB b $ fastZStringToFastBytes fs
+bPutFZS b fs = bPutBS b $ fastZStringToByteString fs
 
 bPutFB :: BufHandle -> FastBytes -> IO ()
-bPutFB b@(BufHandle buf r hdl) fb@(FastBytes len fp) =
- withForeignPtr fp $ \ptr -> do
+bPutFB b (FastBytes len fp) =
+ withForeignPtr fp $ \ptr -> bPutCStringLen b (castPtr ptr, len)
+
+bPutBS :: BufHandle -> ByteString -> IO ()
+bPutBS b bs = BS.unsafeUseAsCStringLen bs $ bPutCStringLen b
+
+bPutCStringLen :: BufHandle -> CStringLen -> IO ()
+bPutCStringLen b@(BufHandle buf r hdl) cstr@(ptr, len) = do
   i <- readFastMutInt r
   if (i + len) >= buf_size
-	then do hPutBuf hdl buf i
-		writeFastMutInt r 0
-		if (len >= buf_size) 
-		    then hPutBuf hdl ptr len
-		    else bPutFB b fb
-	else do
-		copyBytes (buf `plusPtr` i) ptr len
-		writeFastMutInt r (i+len)
+        then do hPutBuf hdl buf i
+                writeFastMutInt r 0
+                if (len >= buf_size)
+                    then hPutBuf hdl ptr len
+                    else bPutCStringLen b cstr
+        else do
+                copyBytes (buf `plusPtr` i) ptr len
+                writeFastMutInt r (i + len)
 
 bPutLitString :: BufHandle -> LitString -> FastInt -> IO ()
 bPutLitString b@(BufHandle buf r hdl) a len_ = a `seq` do