Specializing hash functions for widely used types.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16933 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/cString.ml b/lib/cString.ml
index 823a356797..551b628342 100644
--- a/lib/cString.ml
+++ b/lib/cString.ml
@@ -46,6 +46,7 @@ module type ExtS =
 sig
   include S
   external equal : string -> string -> bool = "caml_string_equal" "noalloc"
+  val hash : string -> int
   val is_empty : string -> bool
   val explode : string -> string list
   val implode : string list -> string
@@ -67,6 +68,16 @@ include String
 
 external equal : string -> string -> bool = "caml_string_equal" "noalloc"
 
+let rec hash len s i accu =
+  if i = len then accu
+  else
+    let c = Char.code (String.unsafe_get s i) in
+    hash len s (succ i) (accu * 19 + c)
+
+let hash s =
+  let len = String.length s in
+  hash len s 0 0
+
 let explode s =
   let rec explode_rec n =
     if n >= String.length s then