1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT LIBRARY COMPONENTS                          --
4--                                                                          --
5--         A D A . C O N T A I N E R S . P R I M E _ N U M B E R S          --
6--                                                                          --
7--                                 S p e c                                  --
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--  This package declares the prime numbers array used to implement hashed
31--  containers. Bucket arrays are always allocated with a prime-number
32--  length (computed using To_Prime below), as this produces better scatter
33--  when hash values are folded.
34
35package Ada.Containers.Prime_Numbers is
36   pragma Pure;
37
38   type Primes_Type is array (Positive range <>) of Hash_Type;
39
40   Primes : constant Primes_Type :=
41     (53,         97,         193,       389,       769,
42      1543,       3079,       6151,      12289,     24593,
43      49157,      98317,      196613,    393241,    786433,
44      1572869,    3145739,    6291469,   12582917,  25165843,
45      50331653,   100663319,  201326611, 402653189, 805306457,
46      1610612741, 3221225473, 4294967291);
47
48   function To_Prime (Length : Count_Type) return Hash_Type;
49   --  Returns the smallest value in Primes not less than Length
50
51end Ada.Containers.Prime_Numbers;
52