[project @ 2005-01-28 14:55:05 by simonmar]

[ghc-base.git] / Data / HashTable.hs

diff --git a/Data/HashTable.hs b/Data/HashTable.hs
index b392ce2..0f31af5 100644 (file)
--- a/Data/HashTable.hs
+++ b/Data/HashTable.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -fno-implicit-prelude #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -187,7 +187,7 @@ new
 
 new cmp hash_fn = do
   -- make a new hash table with a single, empty, segment
-  dir     <- newIOArray (0,dIR_SIZE) undefined
+  dir     <- newIOArray (0,dIR_SIZE-1) undefined
   segment <- newIOArray (0,sEGMENT_SIZE-1) []
   myWriteArray dir 0 segment
 
@@ -271,11 +271,17 @@ expandHashTable
       newsegment = newbucket `shiftR` sEGMENT_SHIFT
       newindex   = newbucket .&. sEGMENT_MASK
   --
-  when (newindex == 0) $
+  if newsegment >= dIR_SIZE    -- make sure we don't overflow the table.
+       then return table
+       else do
+  --
+   when (newindex == 0) $
        do segment <- newIOArray (0,sEGMENT_SIZE-1) []
-          myWriteArray dir newsegment segment
+          writeIOArray dir newsegment segment
+          -- doesn't happen very often, so we might as well use a safe
+          -- array index here.
   --
-  let table' =
+   let table' =
        if (split+1) < max
            then table{ split = split+1,
                        bcount = bcount+1 }
@@ -286,7 +292,7 @@ expandHashTable
                        max_bucket = max * 2,
                        mask1 = mask2,
                        mask2 = mask2 `shiftL` 1 .|. 1 }
-  let
+   let
     split_bucket old new [] = do
        segment <- myReadArray dir oldsegment
        myWriteArray segment oldindex old
@@ -298,10 +304,10 @@ expandHashTable
                then split_bucket old ((k,v):new) xs
                else split_bucket ((k,v):old) new xs
   --
-  segment <- myReadArray dir oldsegment
-  bucket <- myReadArray segment oldindex
-  split_bucket [] [] bucket
-  return table'
+   segment <- myReadArray dir oldsegment
+   bucket <- myReadArray segment oldindex
+   split_bucket [] [] bucket
+   return table'
 
 -- -----------------------------------------------------------------------------
 -- Deleting a mapping from the hash table