gcc/ada/a-stwiha.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --                A D A . S T R I N G S . W I D E _ H A S H                 --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2004-2006, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- This unit was originally developed by Matthew J Heaney.                  --
  30 ------------------------------------------------------------------------------
  31
  32 --  Note: source of this algorithm: GNAT.HTable.Hash (g-htable.adb)
  33
  34 function Ada.Strings.Wide_Hash
  35   (Key : Wide_String) return Containers.Hash_Type
  36 is
  37    use Ada.Containers;
  38
  39    function Rotate_Left
  40      (Value  : Hash_Type;
  41       Amount : Natural) return Hash_Type;
  42    pragma Import (Intrinsic, Rotate_Left);
  43
  44    Tmp : Hash_Type;
  45
  46 begin
  47    Tmp := 0;
  48    for J in Key'Range loop
  49       Tmp := Rotate_Left (Tmp, 3) + Wide_Character'Pos (Key (J));
  50    end loop;
  51
  52    return Tmp;
  53 end Ada.Strings.Wide_Hash;