X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Futils%2FFastString.lhs;h=2558c5630a0d0ebfa27167db48777470c5e761aa;hb=9d7da331989abcd1844e9d03b8d1e4163796fa85;hp=c003f790bf00001219f216299f223205585735cd;hpb=f1c6cec9ba89077b0ae64f980f26cc28c1de9395;p=ghc-hetmet.git

diff --git a/ghc/compiler/utils/FastString.lhs b/ghc/compiler/utils/FastString.lhs
index c003f79..2558c56 100644
--- a/ghc/compiler/utils/FastString.lhs
+++ b/ghc/compiler/utils/FastString.lhs
@@ -1,535 +1,459 @@
 %
-% (c) The GRASP/AQUA Project, Glasgow University, 1997
+% (c) The University of Glasgow, 1997-2006
 %
-\section{Fast strings}
-
-Compact representations of character strings with
-unique identifiers.
-
 \begin{code}
-#include "HsVersions.h"
+{-# OPTIONS -fglasgow-exts -O #-}
 
+{-
+FastString:	A compact, hash-consed, representation of character strings.
+		Comparison is O(1), and you can get a Unique from them.
+		Generated by the FSLIT macro
+		Turn into SDoc with Outputable.ftext
+
+LitString:	Just a wrapper for the Addr# of a C string (Ptr CChar).
+		Practically no operations
+		Outputing them is fast
+		Generated by the SLIT macro
+		Turn into SDoc with Outputable.ptext
+
+Use LitString unless you want the facilities of FastString
+-}
 module FastString
        (
+	-- * FastStrings
 	FastString(..),     -- not abstract, for now.
 
-         --names?
-        mkFastString,       -- :: String -> FastString
-	mkFastCharString,   -- :: _Addr -> FastString
-	mkFastCharString2,  -- :: _Addr -> Int -> FastString
-        mkFastSubString,    -- :: _Addr -> Int -> Int -> FastString
-        mkFastSubStringFO,  -- :: ForeignObj -> Int -> Int -> FastString
-
-	mkFastString#,      -- :: Addr# -> Int# -> FastString
-        mkFastSubStringBA#, -- :: ByteArray# -> Int# -> Int# -> FastString
-        mkFastSubString#,   -- :: Addr# -> Int# -> Int# -> FastString
-        mkFastSubStringFO#, -- :: ForeignObj# -> Int# -> Int# -> FastString
-       
-	lengthFS,	    -- :: FastString -> Int
-	nullFastString,     -- :: FastString -> Bool
-
-	getByteArray#,	    -- :: FastString -> ByteArray#
-        getByteArray,       -- :: FastString -> _ByteArray Int
+	-- ** Construction
+        mkFastString,
+	mkFastStringBytes,
+	mkFastStringForeignPtr,
+	mkFastString#,
+	mkZFastString,
+	mkZFastStringBytes,
+
+	-- ** Deconstruction
 	unpackFS,	    -- :: FastString -> String
-	appendFS,	    -- :: FastString -> FastString -> FastString
-        headFS,		    -- :: FastString -> Char
-        tailFS,		    -- :: FastString -> FastString
-	concatFS,	    -- :: [FastString] -> FastString
-        consFS,             -- :: Char -> FastString -> FastString
-
-        hPutFS,		    -- :: Handle -> FastString -> IO ()
-        tagCmpFS	    -- :: FastString -> FastString -> _CMP_TAG
+	bytesFS,	    -- :: FastString -> [Word8]
+
+	-- ** Encoding
+	isZEncoded,
+	zEncodeFS,
+
+	-- ** Operations
+        uniqueOfFS,
+	lengthFS,
+	nullFS,
+	appendFS,
+        headFS,
+        tailFS,
+	concatFS,
+        consFS,
+	nilFS,
+
+	-- ** Outputing
+        hPutFS,
+
+	-- * LitStrings
+	LitString, 
+	mkLitString#,
+	strLength
        ) where
 
-#if __GLASGOW_HASKELL__ <= 201
-import PreludeGlaST
-import PreludeGlaMisc
-#else
-import GlaExts
-import Foreign
-import IOBase
-import IOHandle
-import ST
-import STBase
-#endif
-import HandleHack
-
-import PrimPacked
-import Ubiq
-
-#define hASH_TBL_SIZE 993
-
-\end{code} 
+-- This #define suppresses the "import FastString" that
+-- HsVersions otherwise produces
+#define COMPILING_FAST_STRING
+#include "HsVersions.h"
 
-@FastString@s are packed representations of strings
-with a unique id for fast comparisons. The unique id
-is assigned when creating the @FastString@, using
-a hash table to map from the character string representation
-to the unique ID.
+import Encoding
 
-\begin{code}
-data FastString
-  = FastString   -- packed repr. on the heap.
-      Int#       -- unique id
-		 --  0 => string literal, comparison
-		 --  will
-      Int#       -- length
-      ByteArray# -- stuff
-
-  | CharStr      -- external C string
-      Addr#      -- pointer to the (null-terminated) bytes in C land.
-      Int#       -- length  (cached)
+import Foreign
+import Foreign.C
+import GLAEXTS
+import UNSAFE_IO	( unsafePerformIO )
+import MONAD_ST		( stToIO )
+import DATA_IOREF	( IORef, newIORef, readIORef, writeIORef )
+import System.IO	( hPutBuf )
 
-instance Eq FastString where
-  a == b = case tagCmpFS a b of { _LT -> False; _EQ -> True;  _GT -> False }
-  a /= b = case tagCmpFS a b of { _LT -> True;  _EQ -> False; _GT -> True  }
+import GHC.Arr		( STArray(..), newSTArray )
+import GHC.IOBase	( IO(..) )
 
-{-
- (FastString u1# _ _) == (FastString u2# _ _) = u1# ==# u2#
--}
+import IO
 
-instance Uniquable FastString where
- uniqueOf (FastString u# _ _) = mkUniqueGrimily u#
- uniqueOf (CharStr a# l#) =
-   {-
-     [A somewhat moby hack]: to avoid entering all sorts
-     of junk into the hash table, all C char strings
-     are by default left out. The benefit of being in
-     the table is that string comparisons are lightning fast,
-     just an Int# comparison.
-   
-     But, if you want to get the Unique of a CharStr, we 
-     enter it into the table and return that unique. This
-     works, but causes the CharStr to be looked up in the hash
-     table each time it is accessed..
-   -}
-   mkUniqueGrimily (case mkFastString# a# l# of { FastString u# _ _ -> u#}) -- Ugh!
-
-instance Uniquable Int where
- uniqueOf (I# i#) = mkUniqueGrimily i#
-
-instance Text FastString  where
-    showsPrec p ps@(FastString u# _ _) r = showsPrec p (unpackFS ps) r
-    showsPrec p ps r = showsPrec p (unpackFS ps) r
-
-getByteArray# :: FastString -> ByteArray#
-getByteArray# (FastString _ _ ba#) = ba#
-
-getByteArray :: FastString -> _ByteArray Int
-getByteArray (FastString _ l# ba#) = _ByteArray (0,I# l#) ba#
+#define hASH_TBL_SIZE  4091
 
-lengthFS :: FastString -> Int
-lengthFS (FastString _ l# _) = I# l#
-lengthFS (CharStr a# l#) = I# l#
-
-nullFastString :: FastString -> Bool
-nullFastString (FastString _ l# _) = l# ==# 0#
-nullFastString (CharStr _ l#) = l# ==# 0#
 
-unpackFS :: FastString -> String
-unpackFS (FastString _ l# ba#) = byteArrayToString (_ByteArray (0,I# l#) ba#)
-unpackFS (CharStr addr len#) =
- unpack 0#
- where
-    unpack nh
-      | nh ==# len# = []
-      | otherwise   = C# ch : unpack (nh +# 1#)
-      where
-	ch = indexCharOffAddr# addr nh
+{-|
+A 'FastString' is an array of bytes, hashed to support fast O(1)
+comparison.  It is also associated with a character encoding, so that
+we know how to convert a 'FastString' to the local encoding, or to the
+Z-encoding used by the compiler internally.
 
-appendFS :: FastString -> FastString -> FastString
-appendFS fs1 fs2 = mkFastString (unpackFS fs1 ++ unpackFS fs2)
+'FastString's support a memoized conversion to the Z-encoding via zEncodeFS.
+-}
 
-concatFS :: [FastString] -> FastString
-concatFS ls = mkFastString (concat (map (unpackFS) ls)) -- ToDo: do better
+data FastString = FastString {
+      uniq    :: {-# UNPACK #-} !Int,       -- unique id
+      n_bytes :: {-# UNPACK #-} !Int,       -- number of bytes
+      n_chars :: {-# UNPACK #-} !Int,	  -- number of chars
+      buf     :: {-# UNPACK #-} !(ForeignPtr Word8),
+      enc     :: FSEncoding
+  }
 
-headFS :: FastString -> Char
-headFS f@(FastString _ l# ba#) = 
- if l# ># 0# then C# (indexCharArray# ba# 0#) else error ("headFS: empty FS: " ++ unpackFS f)
-headFS f@(CharStr a# l#) = 
- if l# ># 0# then C# (indexCharOffAddr# a# 0#) else error ("headFS: empty FS: " ++ unpackFS f)
+data FSEncoding
+  = ZEncoded
+ 	-- including strings that don't need any encoding
+  | UTF8Encoded {-# UNPACK #-} !(IORef (Maybe FastString))
+	-- A UTF-8 string with a memoized Z-encoding
 
-tailFS :: FastString -> FastString
-tailFS (FastString _ l# ba#) = mkFastSubStringBA# ba# 1# (l# -# 1#)
+instance Eq FastString where
+  f1 == f2  =  uniq f1 == uniq f2
 
-consFS :: Char -> FastString -> FastString
-consFS c fs = mkFastString (c:unpackFS fs)
+instance Ord FastString where
+	-- Compares lexicographically, not by unique
+    a <= b = case cmpFS a b of { LT -> True;  EQ -> True;  GT -> False }
+    a <	 b = case cmpFS a b of { LT -> True;  EQ -> False; GT -> False }
+    a >= b = case cmpFS a b of { LT -> False; EQ -> True;  GT -> True  }
+    a >	 b = case cmpFS a b of { LT -> False; EQ -> False; GT -> True  }
+    max x y | x >= y	=  x
+            | otherwise	=  y
+    min x y | x <= y	=  x
+            | otherwise	=  y
+    compare a b = cmpFS a b
+
+instance Show FastString where
+   show fs = show (unpackFS fs)
+
+cmpFS :: FastString -> FastString -> Ordering
+cmpFS (FastString u1 l1 _ buf1 _) (FastString u2 l2 _ buf2 _) =
+  if u1 == u2 then EQ else
+  let l = if l1 <= l2 then l1 else l2 in
+  inlinePerformIO $
+    withForeignPtr buf1 $ \p1 ->
+    withForeignPtr buf2 $ \p2 -> do
+      res <- memcmp p1 p2 l
+      case () of
+       _ | res <  0  -> return LT
+	 | res == 0  -> if l1 == l2 then return EQ 
+				    else if l1 < l2 then return LT
+						    else return GT
+ 	 | otherwise -> return GT
+
+#ifndef __HADDOCK__
+foreign import ccall unsafe "ghc_memcmp" 
+  memcmp :: Ptr a -> Ptr b -> Int -> IO Int
+#endif
 
-\end{code}
+-- -----------------------------------------------------------------------------
+-- Construction
 
+{-
 Internally, the compiler will maintain a fast string symbol
 table, providing sharing and fast comparison. Creation of
 new @FastString@s then covertly does a lookup, re-using the
 @FastString@ if there was a hit.
+-}
 
-\begin{code}
 data FastStringTable = 
  FastStringTable
-    Int#
-    (MutableArray# _RealWorld [FastString])
-
-type FastStringTableVar = MutableVar _RealWorld FastStringTable
+    {-# UNPACK #-} !Int
+    (MutableArray# RealWorld [FastString])
 
-string_table :: FastStringTableVar
+string_table :: IORef FastStringTable
 string_table = 
- unsafePerformPrimIO (
-   newArray (0::Int,hASH_TBL_SIZE) [] `thenPrimIO` \ (_MutableArray _ arr#) ->
-   newVar (FastStringTable 0# arr#))
-
-lookupTbl :: FastStringTable -> Int# -> PrimIO [FastString]
-lookupTbl (FastStringTable _ arr#) i# =
-  MkST ( \ (S# s#) ->
-  case readArray# arr# i# s# of { StateAndPtr# s2# r ->
-    (r, S# s2#) })
-
-updTbl :: FastStringTableVar -> FastStringTable -> Int# -> [FastString] -> PrimIO ()
-updTbl (_MutableArray _ var#) (FastStringTable uid# arr#) i# ls =
- MkST ( \ (S# s#) ->
- case writeArray# arr# i# ls s# of { s2# ->
- case writeArray# var# 0# (FastStringTable (uid# +# 1#) arr#) s2# of { s3# ->
-  ((), S# s3#) }})
-
-mkFastString# :: Addr# -> Int# -> FastString
-mkFastString# a# len# =
- unsafePerformPrimIO  (
-  readVar string_table `thenPrimIO` \ ft@(FastStringTable uid# tbl#) ->
+ unsafePerformIO $ do
+   (STArray _ _ arr#) <- stToIO (newSTArray (0::Int,hASH_TBL_SIZE) [])
+   newIORef (FastStringTable 0 arr#)
+
+lookupTbl :: FastStringTable -> Int -> IO [FastString]
+lookupTbl (FastStringTable _ arr#) (I# i#) =
+  IO $ \ s# -> readArray# arr# i# s#
+
+updTbl :: IORef FastStringTable -> FastStringTable -> Int -> [FastString] -> IO ()
+updTbl fs_table_var (FastStringTable uid arr#) (I# i#) ls = do
+  (IO $ \ s# -> case writeArray# arr# i# ls s# of { s2# -> (# s2#, () #) })
+  writeIORef fs_table_var (FastStringTable (uid+1) arr#)
+
+mkFastString# :: Addr# -> FastString
+mkFastString# a# = mkFastStringBytes ptr (strLength ptr)
+  where ptr = Ptr a#
+
+mkFastStringBytes :: Ptr Word8 -> Int -> FastString
+mkFastStringBytes ptr len = unsafePerformIO $ do
+  ft@(FastStringTable uid tbl#) <- readIORef string_table
   let
-   h = hashStr a# len#
-  in
---  _trace ("hashed: "++show (I# h)) $
-  lookupTbl ft h	`thenPrimIO` \ lookup_result ->
+   h = hashStr ptr len
+   add_it ls = do
+	fs <- copyNewFastString uid ptr len
+	updTbl string_table ft h (fs:ls)
+	{- _trace ("new: " ++ show f_str)   $ -}
+	return fs
+  --
+  lookup_result <- lookupTbl ft h
   case lookup_result of
-    [] -> 
-       -- no match, add it to table by copying out the
-       -- the string into a ByteArray
-       -- _trace "empty bucket" $
-       case copyPrefixStr (A# a#) (I# len#) of
-	 (_ByteArray _ barr#) ->  
-	   let f_str = FastString uid# len# barr# in
-           updTbl string_table ft h [f_str] `seqPrimIO`
-           ({- _trace ("new: " ++ show f_str)   $ -} returnPrimIO f_str)
-    ls -> 
-       -- non-empty `bucket', scan the list looking
-       -- entry with same length and compare byte by byte.
-       -- _trace ("non-empty bucket"++show ls) $
-       case bucket_match ls len# a# of
-	 Nothing -> 
-           case copyPrefixStr (A# a#) (I# len#) of
-  	    (_ByteArray _ barr#) ->  
-              let f_str = FastString uid# len# barr# in
-              updTbl string_table ft h (f_str:ls) `seqPrimIO`
-	      ( {- _trace ("new: " ++ show f_str)  $ -} returnPrimIO f_str)
-	 Just v  -> {- _trace ("re-use: "++show v) $ -} returnPrimIO v)
-  where
-   bucket_match [] _ _ = Nothing
-   bucket_match (v@(FastString _ l# ba#):ls) len# a# =
-      if len# ==# l# && eqStrPrefix a# ba# l# then
-	 Just v
-      else
-	 bucket_match ls len# a#
-
-mkFastSubString# :: Addr# -> Int# -> Int# -> FastString
-mkFastSubString# a# start# len# = mkFastCharString2 (A# (addrOffset# a# start#)) (I# len#)
-
-mkFastSubStringFO# :: ForeignObj# -> Int# -> Int# -> FastString
-mkFastSubStringFO# fo# start# len# =
- unsafePerformPrimIO  (
-  readVar string_table `thenPrimIO` \ ft@(FastStringTable uid# tbl#) ->
+    [] -> add_it []
+    ls -> do
+       b <- bucket_match ls len ptr
+       case b of
+	 Nothing -> add_it ls
+	 Just v  -> {- _trace ("re-use: "++show v) $ -} return v
+
+mkZFastStringBytes :: Ptr Word8 -> Int -> FastString
+mkZFastStringBytes ptr len = unsafePerformIO $ do
+  ft@(FastStringTable uid tbl#) <- readIORef string_table
   let
-   h = hashSubStrFO fo# start# len#
-  in
-  lookupTbl ft h	`thenPrimIO` \ lookup_result ->
+   h = hashStr ptr len
+   add_it ls = do
+	fs <- copyNewZFastString uid ptr len
+	updTbl string_table ft h (fs:ls)
+	{- _trace ("new: " ++ show f_str)   $ -}
+	return fs
+  --
+  lookup_result <- lookupTbl ft h
   case lookup_result of
-    [] -> 
-       -- no match, add it to table by copying out the
-       -- the string into a ByteArray
-       case copySubStrFO (_ForeignObj fo#) (I# start#) (I# len#) of
-	 (_ByteArray _ barr#) ->  
-	   let f_str = FastString uid# len# barr# in
-           updTbl string_table ft h [f_str]       `seqPrimIO`
-	   returnPrimIO f_str
-    ls -> 
-       -- non-empty `bucket', scan the list looking
-       -- entry with same length and compare byte by byte.
-       case bucket_match ls start# len# fo# of
-	 Nothing -> 
-           case copySubStrFO (_ForeignObj fo#) (I# start#) (I# len#) of
-   	     (_ByteArray _ barr#) ->  
-              let f_str = FastString uid# len# barr# in
-              updTbl string_table ft  h (f_str:ls) `seqPrimIO`
-	      ( {- _trace ("new: " ++ show f_str) $ -} returnPrimIO f_str)
-	 Just v  -> {- _trace ("re-use: "++show v) $ -} returnPrimIO v)
-  where
-   bucket_match [] _ _ _ = Nothing
-   bucket_match (v@(FastString _ l# barr#):ls) start# len# fo# =
-      if len# ==# l# && eqStrPrefixFO fo# barr# start# len# then
-	 Just v
-      else
-	 bucket_match ls start# len# fo#
-
-
-mkFastSubStringBA# :: ByteArray# -> Int# -> Int# -> FastString
-mkFastSubStringBA# barr# start# len# =
- unsafePerformPrimIO  (
-  readVar string_table `thenPrimIO` \ ft@(FastStringTable uid# tbl#) ->
+    [] -> add_it []
+    ls -> do
+       b <- bucket_match ls len ptr
+       case b of
+	 Nothing -> add_it ls
+	 Just v  -> {- _trace ("re-use: "++show v) $ -} return v
+
+-- | Create a 'FastString' from an existing 'ForeignPtr'; the difference
+-- between this and 'mkFastStringBytes' is that we don't have to copy
+-- the bytes if the string is new to the table.
+mkFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString
+mkFastStringForeignPtr ptr fp len = do
+  ft@(FastStringTable uid tbl#) <- readIORef string_table
+--  _trace ("hashed: "++show (I# h)) $
   let
-   h = hashSubStrBA barr# start# len#
-  in
---  _trace ("hashed(b): "++show (I# h)) $
-  lookupTbl ft h	`thenPrimIO` \ lookup_result ->
+    h = hashStr ptr len
+    add_it ls = do
+	fs <- mkNewFastString uid ptr fp len
+	updTbl string_table ft h (fs:ls)
+	{- _trace ("new: " ++ show f_str)   $ -}
+	return fs
+  --
+  lookup_result <- lookupTbl ft h
   case lookup_result of
-    [] -> 
-       -- no match, add it to table by copying out the
-       -- the string into a ByteArray
-       -- _trace "empty bucket(b)" $
-       case copySubStrBA (_ByteArray btm barr#) (I# start#) (I# len#) of
-         (_ByteArray _ ba#) ->  
-          let f_str = FastString uid# len# ba# in
-          updTbl string_table ft h [f_str]     `seqPrimIO`
-          -- _trace ("new(b): " ++ show f_str)   $
-	  returnPrimIO f_str
-    ls -> 
-       -- non-empty `bucket', scan the list looking
-       -- entry with same length and compare byte by byte. 
-       -- _trace ("non-empty bucket(b)"++show ls) $
-       case bucket_match ls start# len# barr# of
-	 Nothing -> 
-          case copySubStrBA (_ByteArray (error "") barr#) (I# start#) (I# len#) of
-            (_ByteArray _ ba#) ->  
-              let f_str = FastString uid# len# ba# in
-              updTbl string_table ft h (f_str:ls) `seqPrimIO`
-	      -- _trace ("new(b): " ++ show f_str)   $
-	      returnPrimIO f_str
-	 Just v  -> 
-              -- _trace ("re-use(b): "++show v) $
-	      returnPrimIO v
-  )
- where
-   btm = error ""
-
-   bucket_match [] _ _ _ = Nothing
-   bucket_match (v:ls) start# len# ba# =
-    case v of
-     FastString _ l# barr# ->
-      if len# ==# l# && eqStrPrefixBA barr# ba# start# len# then
-	 Just v
-      else
-	 bucket_match ls start# len# ba#
-
-mkFastCharString :: _Addr -> FastString
-mkFastCharString a@(A# a#) = 
- case strLength a of{ (I# len#) -> CharStr a# len# }
-
-mkFastCharString2 :: _Addr -> Int -> FastString
-mkFastCharString2 a@(A# a#) (I# len#) = CharStr a# len#
+    [] -> add_it []
+    ls -> do
+       b <- bucket_match ls len ptr
+       case b of
+	 Nothing -> add_it ls
+	 Just v  -> {- _trace ("re-use: "++show v) $ -} return v
+
+mkZFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString
+mkZFastStringForeignPtr ptr fp len = do
+  ft@(FastStringTable uid tbl#) <- readIORef string_table
+--  _trace ("hashed: "++show (I# h)) $
+  let
+    h = hashStr ptr len
+    add_it ls = do
+	fs <- mkNewZFastString uid ptr fp len
+	updTbl string_table ft h (fs:ls)
+	{- _trace ("new: " ++ show f_str)   $ -}
+	return fs
+  --
+  lookup_result <- lookupTbl ft h
+  case lookup_result of
+    [] -> add_it []
+    ls -> do
+       b <- bucket_match ls len ptr
+       case b of
+	 Nothing -> add_it ls
+	 Just v  -> {- _trace ("re-use: "++show v) $ -} return v
 
+
+-- | Creates a UTF-8 encoded 'FastString' from a 'String'
 mkFastString :: String -> FastString
 mkFastString str = 
- case stringToByteArray str of
-  (_ByteArray (_,I# len#) frozen#) -> 
-    mkFastSubStringBA# frozen# 0# len#
-    {- 0-indexed array, len# == index to one beyond end of string,
-       i.e., (0,1) => empty string.    -}
+  inlinePerformIO $ do
+    let l = utf8EncodedLength str
+    buf <- mallocForeignPtrBytes l
+    withForeignPtr buf $ \ptr -> do
+      utf8EncodeString ptr str
+      mkFastStringForeignPtr ptr buf l 
+
+
+-- | Creates a Z-encoded 'FastString' from a 'String'
+mkZFastString :: String -> FastString
+mkZFastString str = 
+  inlinePerformIO $ do
+    let l = Prelude.length str
+    buf <- mallocForeignPtrBytes l
+    withForeignPtr buf $ \ptr -> do
+      pokeCAString (castPtr ptr) str
+      mkZFastStringForeignPtr ptr buf l 
+
+bucket_match [] _ _ = return Nothing
+bucket_match (v@(FastString _ l _ buf _):ls) len ptr
+      | len == l  =  do
+	 b <- cmpStringPrefix ptr buf len
+	 if b then return (Just v)
+	      else bucket_match ls len ptr
+      | otherwise = 
+	 bucket_match ls len ptr
+
+mkNewFastString uid ptr fp len = do
+  ref <- newIORef Nothing
+  n_chars <- countUTF8Chars ptr len
+  return (FastString uid len n_chars fp (UTF8Encoded ref))
+
+mkNewZFastString uid ptr fp len = do
+  return (FastString uid len len fp ZEncoded)
+
+
+copyNewFastString uid ptr len = do
+  fp <- copyBytesToForeignPtr ptr len
+  ref <- newIORef Nothing
+  n_chars <- countUTF8Chars ptr len
+  return (FastString uid len n_chars fp (UTF8Encoded ref))
+
+copyNewZFastString uid ptr len = do
+  fp <- copyBytesToForeignPtr ptr len
+  return (FastString uid len len fp ZEncoded)
+
+
+copyBytesToForeignPtr ptr len = do
+  fp <- mallocForeignPtrBytes len
+  withForeignPtr fp $ \ptr' -> copyBytes ptr' ptr len
+  return fp
+
+cmpStringPrefix :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO Bool
+cmpStringPrefix ptr fp len =
+  withForeignPtr fp $ \ptr' -> do
+    r <- memcmp ptr ptr' len
+    return (r == 0)
+
+
+hashStr  :: Ptr Word8 -> Int -> Int
+ -- use the Addr to produce a hash value between 0 & m (inclusive)
+hashStr (Ptr a#) (I# len#) = loop 0# 0#
+   where 
+    loop h n | n ==# len# = I# h
+	     | otherwise  = loop h2 (n +# 1#)
+	  where c = ord# (indexCharOffAddr# a# n)
+		h2 = (c +# (h *# 128#)) `remInt#` hASH_TBL_SIZE#
 
-mkFastSubString :: _Addr -> Int -> Int -> FastString
-mkFastSubString (A# a#) (I# start#) (I# len#) =
- mkFastString# (addrOffset# a# start#) len#
+-- -----------------------------------------------------------------------------
+-- Operations
 
-mkFastSubStringFO :: _ForeignObj -> Int -> Int -> FastString
-mkFastSubStringFO (_ForeignObj fo#) (I# start#) (I# len#) =
- mkFastSubStringFO# fo# start# len#
+-- | Returns the length of the 'FastString' in characters
+lengthFS :: FastString -> Int
+lengthFS f = n_chars f
 
-\end{code}
+-- | Returns 'True' if the 'FastString' is Z-encoded
+isZEncoded :: FastString -> Bool
+isZEncoded fs | ZEncoded <- enc fs = True
+		| otherwise          = False
 
-\begin{code}
-hashStr  :: Addr# -> Int# -> Int#
- -- use the Addr to produce a hash value between 0 & m (inclusive)
-hashStr a# len# =
-  case len# of
-   0# -> 0#
-   1# -> ((ord# c0 *# 631#) +# len#) `remInt#` hASH_TBL_SIZE#
-   2# -> ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# len#) `remInt#` hASH_TBL_SIZE#
-   _  -> ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# (ord# c2 *# 43#) +# len#) `remInt#` hASH_TBL_SIZE#
-{- Currently UNUSED:
-  if len# ==# 0# then
-     0#
-  else
-     ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# (ord# c2 *# 43#) +# len#)
-	`remInt#` hASH_TBL_SIZE#
--}
-  where
-    c0 = indexCharOffAddr# a# 0#
-    c1 = indexCharOffAddr# a# 1# --(len# `quotInt#` 2# -# 1#)
-    c2 = indexCharOffAddr# a# 2# --(len# -# 1#)
+-- | Returns 'True' if the 'FastString' is empty
+nullFS :: FastString -> Bool
+nullFS f  =  n_bytes f == 0
 
-hashSubStrFO  :: ForeignObj# -> Int# -> Int# -> Int#
- -- use the Addr to produce a hash value between 0 & m (inclusive)
-hashSubStrFO fo# start# len# =
-  case len# of
-   0# -> 0#
-   1# -> ((ord# c0 *# 631#) +# len#) `remInt#` hASH_TBL_SIZE#
-   2# -> ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# len#) `remInt#` hASH_TBL_SIZE#
-   _  -> ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# (ord# c2 *# 43#) +# len#) `remInt#` hASH_TBL_SIZE#
-{-
-  if len# ==# 0# then
-     0#
-  else
-     ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# (ord# c2 *# 43#) +# len#)
-	`remInt#` hASH_TBL_SIZE#
--}
-  where
-    c0 = indexCharOffFO# fo# 0#
-    c1 = indexCharOffFO# fo# 1# --(len# `quotInt#` 2# -# 1#)
-    c2 = indexCharOffFO# fo# 2# --(len# -# 1#)
+-- | unpacks and decodes the FastString
+unpackFS :: FastString -> String
+unpackFS (FastString _ n_bytes _ buf enc) = 
+  inlinePerformIO $ withForeignPtr buf $ \ptr ->
+    case enc of
+	ZEncoded      -> peekCAStringLen (castPtr ptr,n_bytes)
+	UTF8Encoded _ -> utf8DecodeString ptr n_bytes
+
+bytesFS :: FastString -> [Word8]
+bytesFS (FastString _ n_bytes _ buf enc) = 
+  inlinePerformIO $ withForeignPtr buf $ \ptr ->
+    peekArray n_bytes ptr
+
+-- | returns a Z-encoded version of a 'FastString'.  This might be the
+-- original, if it was already Z-encoded.  The first time this
+-- function is applied to a particular 'FastString', the results are
+-- memoized.
+--
+zEncodeFS :: FastString -> FastString
+zEncodeFS fs@(FastString uid n_bytes _ fp enc) =
+  case enc of
+    ZEncoded -> fs
+    UTF8Encoded ref ->
+      inlinePerformIO $ do
+        m <- readIORef ref
+        case m of
+	  Just fs -> return fs
+	  Nothing -> do
+            let efs = mkZFastString (zEncodeString (unpackFS fs))
+	    writeIORef ref (Just efs)
+	    return efs
 
+appendFS :: FastString -> FastString -> FastString
+appendFS fs1 fs2 = mkFastString (unpackFS fs1 ++ unpackFS fs2)
 
-hashSubStrBA  :: ByteArray# -> Int# -> Int# -> Int#
- -- use the Addr to produce a hash value between 0 & m (inclusive)
-hashSubStrBA ba# start# len# =
-  case len# of
-   0# -> 0#
-   1# -> ((ord# c0 *# 631#) +# len#) `remInt#` hASH_TBL_SIZE#
-   2# -> ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# len#) `remInt#` hASH_TBL_SIZE#
-   _  -> ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# (ord# c2 *# 43#) +# len#) `remInt#` hASH_TBL_SIZE#
-{-
-  if len# ==# 0# then
-     0#
-  else
-     ((ord# c0 *# 631#) +# (ord# c1 *# 217#) +# (ord# c2 *# 43#) +# len#)
-	`remInt#` hASH_TBL_SIZE#
--}
-  where
-    c0 = indexCharArray# ba# 0#
-    c1 = indexCharArray# ba# 1# --(len# `quotInt#` 2# -# 1#)
-    c2 = indexCharArray# ba# 2# --(len# -# 1#)
+concatFS :: [FastString] -> FastString
+concatFS ls = mkFastString (Prelude.concat (map unpackFS ls)) -- ToDo: do better
 
-\end{code}
+headFS :: FastString -> Char
+headFS (FastString _ n_bytes _ buf enc) = 
+  inlinePerformIO $ withForeignPtr buf $ \ptr -> do
+    case enc of
+      ZEncoded -> do 
+	 w <- peek (castPtr ptr)
+	 return (castCCharToChar w)
+      UTF8Encoded _ -> 
+	 return (fst (utf8DecodeChar ptr))
 
-\begin{code}
-tagCmpFS :: FastString -> FastString -> _CMP_TAG
-tagCmpFS (FastString u1# _ b1#) (FastString u2# _ b2#) = -- assume non-null chars
-  if u1# ==# u2# then
-     _EQ
-  else
-   unsafePerformPrimIO (
-    _ccall_ strcmp (_ByteArray bottom b1#) (_ByteArray bottom b2#) `thenPrimIO` \ (I# res) ->
-    returnPrimIO (
-    if      res <#  0# then _LT
-    else if res ==# 0# then _EQ
-    else		    _GT
-    ))
-  where
-   bottom :: (Int,Int)
-   bottom = error "tagCmp"
-tagCmpFS (CharStr bs1 len1) (CharStr bs2 len2)
-  = unsafePerformPrimIO (
-    _ccall_ strcmp ba1 ba2  `thenPrimIO` \ (I# res) ->
-    returnPrimIO (
-    if      res <#  0# then _LT
-    else if res ==# 0# then _EQ
-    else		    _GT
-    ))
-  where
-    ba1 = A# bs1
-    ba2 = A# bs2
-tagCmpFS (FastString _ len1 bs1) (CharStr bs2 len2)
- = unsafePerformPrimIO (
-    _ccall_ strcmp ba1 ba2 `thenPrimIO` \ (I# res) ->
-    returnPrimIO (
-     if      res <#  0# then _LT
-     else if res ==# 0# then _EQ
-     else		    _GT
-    ))
-  where
-    ba1 = _ByteArray ((error "")::(Int,Int)) bs1
-    ba2 = A# bs2
-
-tagCmpFS a@(CharStr _ _) b@(FastString _ _ _)
-  = -- try them the other way 'round
-    case (tagCmpFS b a) of { _LT -> _GT; _EQ -> _EQ; _GT -> _LT }
+tailFS :: FastString -> FastString
+tailFS (FastString _ n_bytes _ buf enc) = 
+  inlinePerformIO $ withForeignPtr buf $ \ptr -> do
+    case enc of
+      ZEncoded -> do
+	return $! mkZFastStringBytes (ptr `plusPtr` 1) (n_bytes - 1)
+      UTF8Encoded _ -> do
+	 let (_,ptr') = utf8DecodeChar ptr
+	 let off = ptr' `minusPtr` ptr
+	 return $! mkFastStringBytes (ptr `plusPtr` off) (n_bytes - off)
 
-instance Ord FastString where
-    a <= b = case tagCmpFS a b of { _LT -> True;  _EQ -> True;  _GT -> False }
-    a <	 b = case tagCmpFS a b of { _LT -> True;  _EQ -> False; _GT -> False }
-    a >= b = case tagCmpFS a b of { _LT -> False; _EQ -> True;  _GT -> True  }
-    a >	 b = case tagCmpFS a b of { _LT -> False; _EQ -> False; _GT -> True  }
-    max x y | x >= y	=  x
-            | otherwise	=  y
-    min x y | x <= y	=  x
-            | otherwise	=  y
-    _tagCmp a b = tagCmpFS a b
+consFS :: Char -> FastString -> FastString
+consFS c fs = mkFastString (c : unpackFS fs)
 
-\end{code}
+uniqueOfFS :: FastString -> Int#
+uniqueOfFS (FastString (I# u#) _ _ _ _) = u#
 
-Outputting @FastString@s is quick, just block copying the chunk (using
-@fwrite@).
+nilFS = mkFastString ""
 
-\begin{code}
-#if __GLASGOW_HASKELL__ >= 201
-#define _ErrorHandle IOBase.ErrorHandle
-#define _ReadHandle IOBase.ReadHandle
-#define _ClosedHandle IOBase.ClosedHandle
-#define _SemiClosedHandle IOBase.SemiClosedHandle
-#define _constructError  IOBase.constructError
-#define _filePtr IOHandle.filePtr
-#define failWith fail
-#endif
+-- -----------------------------------------------------------------------------
+-- Outputting 'FastString's
+
+-- |Outputs a 'FastString' with /no decoding at all/, that is, you
+-- get the actual bytes in the 'FastString' written to the 'Handle'.
+hPutFS handle (FastString _ len _ fp _)
+  | len == 0  = return ()
+  | otherwise = do withForeignPtr fp $ \ptr -> hPutBuf handle ptr len
+
+-- ToDo: we'll probably want an hPutFSLocal, or something, to output
+-- in the current locale's encoding (for error messages and suchlike).
+
+-- -----------------------------------------------------------------------------
+-- LitStrings, here for convenience only.
+
+type LitString = Ptr ()
+
+mkLitString# :: Addr# -> LitString
+mkLitString# a# = Ptr a#
+
+foreign import ccall unsafe "ghc_strlen" 
+  strLength :: Ptr () -> Int
+
+-- -----------------------------------------------------------------------------
+-- under the carpet
+
+-- Just like unsafePerformIO, but we inline it.
+{-# INLINE inlinePerformIO #-}
+inlinePerformIO :: IO a -> a
+inlinePerformIO (IO m) = case m realWorld# of (# _, r #)   -> r
+
+pokeCAString :: Ptr CChar -> String -> IO ()
+pokeCAString ptr str =
+  let
+	go [] n     = pokeElemOff ptr n 0
+    	go (c:cs) n = do pokeElemOff ptr n (castCharToCChar c); go cs (n+1)
+  in
+  go str 0
 
-hPutFS :: Handle -> FastString -> IO ()
-hPutFS handle (FastString _ l# ba#) =
- if l# ==# 0# then
-    return ()
- else
-    _readHandle handle				    >>= \ htype ->
-    case htype of 
-      _ErrorHandle ioError ->
-	  _writeHandle handle htype		    >>
-          failWith ioError
-      _ClosedHandle ->
-	  _writeHandle handle htype		    >>
-	  failWith MkIOError(handle,IllegalOperation,"handle is closed")
-      _SemiClosedHandle _ _ ->
-	  _writeHandle handle htype		    >>
-	  failWith MkIOError(handle,IllegalOperation,"handle is closed")
-      _ReadHandle _ _ _ ->
-	  _writeHandle handle htype		    >>
-	  failWith MkIOError(handle,IllegalOperation,"handle is not open for writing")
-      other -> 
-          let fp = _filePtr htype in
-	   -- here we go..
-          _ccall_ writeFile (_ByteArray ((error "")::(Int,Int)) ba#) fp (I# l#) `CCALL_THEN` \rc ->
-          if rc==0 then
-              return ()
-          else
-              _constructError "hPutFS"   `CCALL_THEN` \ err ->
-	      failWith err
-hPutFS handle (CharStr a# l#) =
- if l# ==# 0# then
-    return ()
- else
-    _readHandle handle				    >>= \ htype ->
-    case htype of 
-      _ErrorHandle ioError ->
-	  _writeHandle handle htype		    >>
-          failWith ioError
-      _ClosedHandle ->
-	  _writeHandle handle htype		    >>
-	  failWith MkIOError(handle,IllegalOperation,"handle is closed")
-      _SemiClosedHandle _ _ ->
-	  _writeHandle handle htype		    >>
-	  failWith MkIOError(handle,IllegalOperation,"handle is closed")
-      _ReadHandle _ _ _ ->
-	  _writeHandle handle htype		    >>
-	  failWith MkIOError(handle,IllegalOperation,"handle is not open for writing")
-      other -> 
-          let fp = _filePtr htype in
-	   -- here we go..
-          _ccall_ writeFile (A# a#) fp (I# l#) `CCALL_THEN` \rc ->
-          if rc==0 then
-              return ()
-          else
-              _constructError "hPutFS"   `CCALL_THEN` \ err ->
-	      failWith err
-
---ToDo: avoid silly code duplic.
 \end{code}