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-- This file is part of 'Finite Field Arithmetic', aka 'FFA'.               --
--                                                                          --
-- (C) 2019 Stanislav Datskovskiy ( www.loper-os.org )                      --
-- http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     --
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-- continue doing so for the indefinite future. In any case, please         --
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-- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     --
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with Words;   use Words;
with FZ_Type; use FZ_Type;


package FZ_Barr is
   
   pragma Pure;
   
   -- Precomputed data for Barrett's Modular Reduction
   type Barretoid(ZXMLength       : Indices;
                  BarretoidLength : Indices) is
      record
         ZXM            : FZ(1 .. ZXMLength);       -- Zero-Extended Modulus
         J              : FZBit_Index;              -- Jm
         B              : FZ(1 .. BarretoidLength); -- The Barrettoid itself
         ZSlide         : FZBit_Index;              -- Amount to slide Z
         Degenerate     : WBool;                    -- Is it degenerate case?
      end record;
   
   
   -- Prepare the precomputed Barrettoid corresponding to a given Modulus
   procedure FZ_Make_Barrettoid(Modulus    : in  FZ;
                                Result     : out Barretoid)
     with Pre => Result.B'Length = 2 * Modulus'Length and
     Result.ZXM'Length = Modulus'Length + 1;
   
   
   -- Reduce N using the given precomputed Barrettoid.
   procedure FZ_Barrett_Reduce(X          : in     FZ;
                               Bar        : in     Barretoid;
                               XReduced   : in out FZ);
   pragma Inline_Always(FZ_Barrett_Reduce);
   
end FZ_Barr;