[MLton-commit] r5021

[Vesa Karvonen]

Initial commit of a lib of misc utils to be refactored.
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A   mltonlib/trunk/com/ssh/misc-util/unstable/cache.sml

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Added: mltonlib/trunk/com/ssh/misc-util/unstable/cache.sml
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--- mltonlib/trunk/com/ssh/misc-util/unstable/cache.sml	2007-01-12 12:24:45 UTC (rev 5020)
+++ mltonlib/trunk/com/ssh/misc-util/unstable/cache.sml	2007-01-12 12:24:57 UTC (rev 5021)
@@ -0,0 +1,58 @@
+(* Copyright (C) 2007 SSH Communications Security, Helsinki, Finland
+ *
+ * This code is released under the MLton license, a BSD-style license.
+ * See the LICENSE file or http://mlton.org/License for details.
+ *)
+
+(**
+ * This cache implementation is basically an imperative separate chaining
+ * hashtable.  The keys are generated using a quick-and-dirty pseudo RNG.
+ *)
+structure Cache :> CACHE where type Key.t = MLRep.Long.Unsigned.word = struct
+   structure T = WordTable and A = WordTable.Action
+         and W = WordTable.Key
+         and Dbg = MkDbg (open DbgDefs val name = "Cache")
+
+   structure Key = struct
+      open MLRep.Long.Unsigned
+      type t = word
+   end
+
+   val () = Dbg.verify (W.wordSize <= Key.wordSize)
+
+   datatype 'a t = IN of {table : 'a T.t, seed : W.t ref}
+
+   exception NotFound
+
+   val (keyToWord, wordToKey) =
+       Iso.<--> (Iso.swap W.isoLarge, (Key.toLarge, Key.fromLarge))
+
+   fun new () = IN {table = T.new (), seed = ref 0w0}
+
+   fun size (IN {table, ...}) = T.size table
+
+   fun putWith (t as IN {table, seed}) keyToValue = let
+      val word = !seed before seed := Misc.ranqd1 (!seed)
+      val key = wordToKey word
+   in
+      case T.access
+              table word
+              (A.peek {some = fn () => A.return NONE,
+                       none = fn () => let
+                                 val value = keyToValue key
+                              in
+                                 A.insert value (SOME value)
+                              end}) of
+         NONE => putWith t keyToValue
+       | SOME value => (key, value)
+   end
+
+   fun put t = #1 o putWith t o const
+
+   fun access action (IN {table, ...}) key =
+       T.access table (keyToWord key) action
+
+   fun get ? = access (A.get {none = failing NotFound, some = A.return}) ?
+   fun use ? = access (A.get {none = failing NotFound, some = A.remove}) ?
+   fun rem ? = access (A.peek {none = failing NotFound, some = A.remove}) ?
+end


Property changes on: mltonlib/trunk/com/ssh/misc-util/unstable/cache.sml
___________________________________________________________________
Name: svn:eol-style
   + native