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ffa_ch14_barrett.kv     1 ------------------------------------------------------------------------------
ffa_ch14_barrett.kv     2 ------------------------------------------------------------------------------
ffa_ch14_barrett.kv     3 -- This file is part of 'Finite Field Arithmetic', aka 'FFA'.               --
ffa_ch14_barrett.kv     4 --                                                                          --
ffa_ch15_gcd.kv         5 -- (C) 2019 Stanislav Datskovskiy ( www.loper-os.org )                      --
ffa_ch14_barrett.kv     6 -- http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     --
ffa_ch14_barrett.kv     7 --                                                                          --
ffa_ch14_barrett.kv     8 -- You do not have, nor can you ever acquire the right to use, copy or      --
ffa_ch14_barrett.kv     9 -- distribute this software ; Should you use this software for any purpose, --
ffa_ch14_barrett.kv    10 -- or copy and distribute it to anyone or in any manner, you are breaking   --
ffa_ch14_barrett.kv    11 -- the laws of whatever soi-disant jurisdiction, and you promise to         --
ffa_ch14_barrett.kv    12 -- continue doing so for the indefinite future. In any case, please         --
ffa_ch14_barrett.kv    13 -- always : read and understand any software ; verify any PGP signatures    --
ffa_ch14_barrett.kv    14 -- that you use - for any purpose.                                          --
ffa_ch14_barrett.kv    15 --                                                                          --
ffa_ch14_barrett.kv    16 -- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     --
ffa_ch14_barrett.kv    17 ------------------------------------------------------------------------------
ffa_ch14_barrett.kv    18 ------------------------------------------------------------------------------
ffa_ch14_barrett.kv    19 
ffa_ch14_barrett.kv    20 with Words;   use Words;
ffa_ch14_barrett.kv    21 with FZ_Type; use FZ_Type;
ffa_ch14_barrett.kv    22 
ffa_ch14_barrett.kv    23 
ffa_ch14_barrett.kv    24 package FZ_Barr is
ffa_ch14_barrett.kv    25    
ffa_ch14_barrett.kv    26    pragma Pure;
ffa_ch14_barrett.kv    27    
ffa_ch14_barrett.kv    28    -- Precomputed data for Barrett's Modular Reduction
ffa_ch14_barrett.kv    29    type Barretoid(ZXMLength       : Indices;
ffa_ch14_barrett.kv    30                   BarretoidLength : Indices) is
ffa_ch14_barrett.kv    31       record
ffa_ch14_barrett.kv    32          ZXM            : FZ(1 .. ZXMLength);       -- Zero-Extended Modulus
ffa_ch14_barrett.kv    33          J              : FZBit_Index;              -- Jm
ffa_ch14_barrett.kv    34          B              : FZ(1 .. BarretoidLength); -- The Barrettoid itself
ffa_ch14_barrett.kv    35          ZSlide         : FZBit_Index;              -- Amount to slide Z
ffa_ch14_barrett.kv    36          Degenerate     : WBool;                    -- Is it degenerate case?
ffa_ch14_barrett.kv    37       end record;
ffa_ch14_barrett.kv    38    
ffa_ch14_barrett.kv    39    
ffa_ch14_barrett.kv    40    -- Prepare the precomputed Barrettoid corresponding to a given Modulus
ffa_ch14_barrett.kv    41    procedure FZ_Make_Barrettoid(Modulus    : in  FZ;
ffa_ch14_barrett.kv    42                                 Result     : out Barretoid)
ffa_ch14_barrett.kv    43      with Pre => Result.B'Length = 2 * Modulus'Length and
ffa_ch14_barrett.kv    44      Result.ZXM'Length = Modulus'Length + 1;
ffa_ch14_barrett.kv    45    
ffa_ch14_barrett.kv    46    
ffa_ch14_barrett.kv    47    -- Reduce N using the given precomputed Barrettoid.
ffa_ch14_barrett.kv    48    procedure FZ_Barrett_Reduce(X          : in     FZ;
ffa_ch14_barrett.kv    49                                Bar        : in     Barretoid;
ffa_ch14_barrett.kv    50                                XReduced   : in out FZ);
ffa_ch14_barrett.kv    51    pragma Inline_Always(FZ_Barrett_Reduce);
ffa_ch14_barrett.kv    52    
ffa_ch14_barrett.kv    53 end FZ_Barr;