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ffa_ch5_egypt.kv        1 ------------------------------------------------------------------------------
ffa_ch5_egypt.kv        2 ------------------------------------------------------------------------------
ffa_ch5_egypt.kv        3 -- This file is part of 'Finite Field Arithmetic', aka 'FFA'.               --
ffa_ch5_egypt.kv        4 --                                                                          --
ffa_ch5_egypt.kv        5 -- (C) 2017 Stanislav Datskovskiy ( www.loper-os.org )                      --
ffa_ch5_egypt.kv        6 -- http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     --
ffa_ch5_egypt.kv        7 --                                                                          --
ffa_ch5_egypt.kv        8 -- You do not have, nor can you ever acquire the right to use, copy or      --
ffa_ch5_egypt.kv        9 -- distribute this software ; Should you use this software for any purpose, --
ffa_ch5_egypt.kv       10 -- or copy and distribute it to anyone or in any manner, you are breaking   --
ffa_ch5_egypt.kv       11 -- the laws of whatever soi-disant jurisdiction, and you promise to         --
ffa_ch5_egypt.kv       12 -- continue doing so for the indefinite future. In any case, please         --
ffa_ch5_egypt.kv       13 -- always : read and understand any software ; verify any PGP signatures    --
ffa_ch5_egypt.kv       14 -- that you use - for any purpose.                                          --
ffa_ch5_egypt.kv       15 --                                                                          --
ffa_ch5_egypt.kv       16 -- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     --
ffa_ch5_egypt.kv       17 ------------------------------------------------------------------------------
ffa_ch5_egypt.kv       18 ------------------------------------------------------------------------------
ffa_ch5_egypt.kv       19 
ffa_ch5_egypt.kv       20 with Words;    use Words;
ffa_ch7_turbo_egy...   21 with W_Shifts; use W_Shifts;
ffa_ch5_egypt.kv       22 with FZ_Basic; use FZ_Basic;
ffa_ch5_egypt.kv       23 with FZ_Arith; use FZ_Arith;
ffa_ch5_egypt.kv       24 with FZ_Shift; use FZ_Shift;
ffa_ch5_egypt.kv       25 
ffa_ch5_egypt.kv       26 
ffa_ch5_egypt.kv       27 package body FZ_Mul is
ffa_ch5_egypt.kv       28    
ffa_ch5_egypt.kv       29    -- 'Egyptological' multiplier. XY_Lo and XY_Hi hold result of X*Y.
ffa_ch5_egypt.kv       30    procedure FZ_Mul_Egyptian(X     : in  FZ;
ffa_ch5_egypt.kv       31                              Y     : in  FZ;
ffa_ch5_egypt.kv       32                              XY_Lo : out FZ;
ffa_ch5_egypt.kv       33                              XY_Hi : out FZ) is
ffa_ch5_egypt.kv       34       
ffa_ch7_turbo_egy...   35       L : constant Indices := X'Length;
ffa_ch7_turbo_egy...   36       
ffa_ch5_egypt.kv       37       -- Register holding running product
ffa_ch5_egypt.kv       38       XY : FZ(1 .. X'Length + Y'Length);
ffa_ch5_egypt.kv       39       
ffa_ch5_egypt.kv       40       -- X-Slide
ffa_ch5_egypt.kv       41       XS : FZ(1 .. X'Length + Y'Length);
ffa_ch5_egypt.kv       42       
ffa_ch5_egypt.kv       43    begin
ffa_ch5_egypt.kv       44       -- Product register begins empty
ffa_ch5_egypt.kv       45       FZ_Clear(XY);
ffa_ch5_egypt.kv       46       
ffa_ch5_egypt.kv       47       -- X-Slide initially equals X:
ffa_ch5_egypt.kv       48       XS(1            .. X'Length) := X;
ffa_ch5_egypt.kv       49       XS(X'Length + 1 .. XS'Last)  := (others => 0);
ffa_ch5_egypt.kv       50       
ffa_ch7_turbo_egy...   51       -- For each word of Y:
ffa_ch7_turbo_egy...   52       for i in Y'Range loop
ffa_ch5_egypt.kv       53          
ffa_ch7_turbo_egy...   54          declare
ffa_ch7_turbo_egy...   55             -- Current word of Y
ffa_ch7_turbo_egy...   56             W : Word  := Y(i);
ffa_ch7_turbo_egy...   57             
ffa_ch7_turbo_egy...   58             -- Current cut of XY and XS. Stay ahead by a word to handle carry.
ffa_ch7_turbo_egy...   59             Cut : constant Indices := L + i;
ffa_ch7_turbo_egy...   60             XYc : FZ renames XY(1 .. Cut);
ffa_ch7_turbo_egy...   61             XSc : FZ renames XS(1 .. Cut);
ffa_ch7_turbo_egy...   62             
ffa_ch7_turbo_egy...   63          begin
ffa_ch7_turbo_egy...   64             for b in 1 .. Bitness loop
ffa_ch7_turbo_egy...   65                
ffa_ch7_turbo_egy...   66                -- If current Y bit is 1, X-Slide Cut is added into XY Cut
ffa_ch7_turbo_egy...   67                FZ_Add_Gated(X    => XYc, Y => XSc, Sum => XYc,
ffa_ch7_turbo_egy...   68                             Gate => W and 1);
ffa_ch7_turbo_egy...   69                
ffa_ch7_turbo_egy...   70                -- Crank the next bit of Y into the bottom position of W
ffa_ch7_turbo_egy...   71                W := Shift_Right(W, 1);
ffa_ch7_turbo_egy...   72                
ffa_ch7_turbo_egy...   73                -- X-Slide := X-Slide * 2
ffa_ch7_turbo_egy...   74                FZ_ShiftLeft(XSc, XSc, 1);
ffa_ch7_turbo_egy...   75                
ffa_ch7_turbo_egy...   76             end loop;
ffa_ch7_turbo_egy...   77          end;
ffa_ch5_egypt.kv       78          
ffa_ch5_egypt.kv       79       end loop;
ffa_ch5_egypt.kv       80       
ffa_ch5_egypt.kv       81       -- Write out the Product's lower and upper FZs:
ffa_ch5_egypt.kv       82       XY_Lo := XY(1                .. XY_Lo'Length);
ffa_ch5_egypt.kv       83       XY_Hi := XY(XY_Lo'Length + 1 .. XY'Last);
ffa_ch5_egypt.kv       84       
ffa_ch5_egypt.kv       85    end FZ_Mul_Egyptian;
ffa_ch5_egypt.kv       86    pragma Inline_Always(FZ_Mul_Egyptian);
ffa_ch5_egypt.kv       87 
ffa_ch5_egypt.kv       88 end FZ_Mul;