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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_ch14_barrett.kv     5 -- (C) 2018 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 FZ_Type; use FZ_Type;
ffa_ch14_barrett.kv    21 
ffa_ch14_barrett.kv    22 
ffa_ch14_barrett.kv    23 -- "Low Multiplication" computes only the bottom half of the product XY.
ffa_ch14_barrett.kv    24 -- Presently, it is used solely in Barrett's Modular Reduction.
ffa_ch14_barrett.kv    25 
ffa_ch14_barrett.kv    26 package FZ_LoMul is
ffa_ch14_barrett.kv    27    
ffa_ch14_barrett.kv    28    pragma Pure;
ffa_ch14_barrett.kv    29    
ffa_ch14_barrett.kv    30    -- Threshhold for Low Mul - at or below this many Words, we use Comba mult.
ffa_ch14_barrett.kv    31    Low_Mul_Thresh : constant Indices := 8;
ffa_ch14_barrett.kv    32    
ffa_ch14_barrett.kv    33    -- Multiply. (CAUTION: UNBUFFERED)
ffa_ch14_barrett.kv    34    procedure FZ_Low_Multiply_Unbuffered(X     : in  FZ;
ffa_ch14_barrett.kv    35                                         Y     : in  FZ;
ffa_ch14_barrett.kv    36                                         XY    : out FZ);
ffa_ch14_barrett.kv    37    pragma Inline_Always(FZ_Low_Multiply_Unbuffered);
ffa_ch14_barrett.kv    38    
ffa_ch14_barrett.kv    39    -- Comba's multiplier. (CAUTION: UNBUFFERED)
ffa_ch14_barrett.kv    40    procedure FZ_Low_Mul_Comba(X     : in  FZ;
ffa_ch14_barrett.kv    41                               Y     : in  FZ;
ffa_ch14_barrett.kv    42                               XY    : out FZ);
ffa_ch14_barrett.kv    43    pragma Inline_Always(FZ_Low_Mul_Comba);
ffa_ch14_barrett.kv    44    
ffa_ch14_barrett.kv    45    -- Low Multiplier. (CAUTION: UNBUFFERED)
ffa_ch14_barrett.kv    46    procedure Low_Mul(X  : in  FZ;
ffa_ch14_barrett.kv    47                      Y  : in  FZ;
ffa_ch14_barrett.kv    48                      XY : out FZ)
ffa_ch14_barrett.kv    49      with Pre => X'Length = Y'Length and
ffa_ch14_barrett.kv    50      XY'Length = X'Length and
ffa_ch14_barrett.kv    51      X'Length mod 2 = 0;
ffa_ch14_barrett.kv    52    -- CAUTION: Inlining prohibited for Low_Mul !
ffa_ch14_barrett.kv    53    
ffa_ch14_barrett.kv    54 end FZ_LoMul;