X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Futils%2FFastString.lhs;h=8dbfefaa0b7690aae3b1a43b8814205c079e841e;hb=423d477bfecd490de1449c59325c8776f91d7aac;hp=ed81d7947e5267c3b8f5bdc7dc155048c397e7f2;hpb=931f16bbdcf82221a29fe404af604b9372dc60c4;p=ghc-hetmet.git

diff --git a/ghc/compiler/utils/FastString.lhs b/ghc/compiler/utils/FastString.lhs
index ed81d79..8dbfefa 100644
--- a/ghc/compiler/utils/FastString.lhs
+++ b/ghc/compiler/utils/FastString.lhs
@@ -3,8 +3,18 @@
 %
 \section{Fast strings}
 
-Compact representations of character strings with
-unique identifiers (hash-cons'ish).
+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
 
 \begin{code}
 module FastString
@@ -106,6 +116,7 @@ instance Eq FastString where
   a /= b = case cmpFS a b of { LT -> True;  EQ -> False; GT -> True  }
 
 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  }
@@ -391,9 +402,9 @@ hashSubStrBA ba# start# len# =
    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#
   where
-    c0 = indexCharArray# ba# 0#
-    c1 = indexCharArray# ba# (len# `quotInt#` 2# -# 1#)
-    c2 = indexCharArray# ba# (len# -# 1#)
+    c0 = indexCharArray# ba# (start# +# 0#)
+    c1 = indexCharArray# ba# (start# +# (len# `quotInt#` 2# -# 1#))
+    c2 = indexCharArray# ba# (start# +# (len# -# 1#))
 
 --    c1 = indexCharArray# ba# 1#
 --    c2 = indexCharArray# ba# 2#
@@ -422,7 +433,7 @@ cmpFS (FastString u1# l1# b1#) (FastString u2# l2# b2#) =
   if u1# ==# u2# then EQ else
   let l# = if l1# <=# l2# then l1# else l2# in
   unsafePerformIO (
-    strncmp b1# b2# l# >>= \ (I# res) ->
+    memcmp b1# b2# l# >>= \ (I# res) ->
     return (
     if      res <#  0# then LT
     else if res ==# 0# then 
@@ -431,8 +442,8 @@ cmpFS (FastString u1# l1# b1#) (FastString u2# l2# b2#) =
     else		    GT
     ))
 
-foreign import ccall "strncmp" unsafe 
-  strncmp :: ByteArray# -> ByteArray# -> Int# -> IO Int
+foreign import ccall "ghc_memcmp" unsafe 
+  memcmp :: ByteArray# -> ByteArray# -> Int# -> IO Int
 
 -- -----------------------------------------------------------------------------
 -- Outputting 'FastString's
@@ -497,7 +508,6 @@ hPutFS handle (UnicodeStr _ is)
 -- LitStrings, here for convenience only.
 
 type LitString = Ptr ()
--- ToDo: make it a Ptr when we don't have to support 4.08 any more
 
 mkLitString# :: Addr# -> LitString
 mkLitString# a# = Ptr a#