Natools

File src/natools-static_hash_maps-s_expressions-command_map.adb artifact e6140e570c part of check-in e3eb7b3d2d

with Interfaces; use Interfaces;

package body Natools.Static_Hash_Maps.S_Expressions.Command_Map is

   P : constant array (0 .. 0) of Natural :=
     (0 .. 0 => 3);

   T1 : constant array (0 .. 0) of Unsigned_8 :=
     (0 .. 0 => 8);

   T2 : constant array (0 .. 0) of Unsigned_8 :=
     (0 .. 0 => 5);

   G : constant array (0 .. 8) of Unsigned_8 :=
     (0, 0, 0, 0, 3, 1, 0, 2, 0);

   function Hash (S : String) return Natural is
      F : constant Natural := S'First - 1;
      L : constant Natural := S'Length;
      F1, F2 : Natural := 0;
      J : Natural;
   begin
      for K in P'Range loop
         exit when L < P (K);
         J  := Character'Pos (S (P (K) + F));
         F1 := (F1 + Natural (T1 (K)) * J) mod 9;
         F2 := (F2 + Natural (T2 (K)) * J) mod 9;
      end loop;
      return (Natural (G (F1)) + Natural (G (F2))) mod 4;
   end Hash;

end Natools.Static_Hash_Maps.S_Expressions.Command_Map;