gcc/ada/a-strhas.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --                     A D A . S T R I N G S . H A S H                      --
   6 --                                                                          --
   7 --                                B o d y                                   --
   8 --                                                                          --
   9 --          Copyright (C) 2004-2009, 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 3,  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.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- This unit was originally developed by Matthew J Heaney.                  --
  28 ------------------------------------------------------------------------------
  29
  30 --  Note: source of this algorithm: GNAT.HTable.Hash (g-htable.adb)
  31
  32 function Ada.Strings.Hash (Key : String) return Containers.Hash_Type is
  33    use Ada.Containers;
  34
  35    function Rotate_Left
  36      (Value  : Hash_Type;
  37       Amount : Natural) return Hash_Type;
  38    pragma Import (Intrinsic, Rotate_Left);
  39
  40    Tmp : Hash_Type;
  41
  42 begin
  43    Tmp := 0;
  44    for J in Key'Range loop
  45       Tmp := Rotate_Left (Tmp, 3) + Character'Pos (Key (J));
  46    end loop;
  47
  48    return Tmp;
  49 end Ada.Strings.Hash;