gcc/ada/a-coprnu.ads

   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
  35 package 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
  51 end Ada.Containers.Prime_Numbers;