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ffa_ch11_tuning_a...    1 ------------------------------------------------------------------------------
ffa_ch11_tuning_a...    2 ------------------------------------------------------------------------------
ffa_ch11_tuning_a...    3 -- This file is part of 'Finite Field Arithmetic', aka 'FFA'.               --
ffa_ch11_tuning_a...    4 --                                                                          --
ffa_ch15_gcd.kv         5 -- (C) 2019 Stanislav Datskovskiy ( www.loper-os.org )                      --
ffa_ch11_tuning_a...    6 -- http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     --
ffa_ch11_tuning_a...    7 --                                                                          --
ffa_ch11_tuning_a...    8 -- You do not have, nor can you ever acquire the right to use, copy or      --
ffa_ch11_tuning_a...    9 -- distribute this software ; Should you use this software for any purpose, --
ffa_ch11_tuning_a...   10 -- or copy and distribute it to anyone or in any manner, you are breaking   --
ffa_ch11_tuning_a...   11 -- the laws of whatever soi-disant jurisdiction, and you promise to         --
ffa_ch11_tuning_a...   12 -- continue doing so for the indefinite future. In any case, please         --
ffa_ch11_tuning_a...   13 -- always : read and understand any software ; verify any PGP signatures    --
ffa_ch11_tuning_a...   14 -- that you use - for any purpose.                                          --
ffa_ch11_tuning_a...   15 --                                                                          --
ffa_ch11_tuning_a...   16 -- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     --
ffa_ch11_tuning_a...   17 ------------------------------------------------------------------------------
ffa_ch11_tuning_a...   18 ------------------------------------------------------------------------------
ffa_ch11_tuning_a...   19 
ffa_ch11_tuning_a...   20 with W_Pred;   use W_Pred;
ffa_ch11_tuning_a...   21 with W_Shifts; use W_Shifts;
ffa_ch11_tuning_a...   22 with FZ_BitOp; use FZ_BitOp;
ffa_ch11_tuning_a...   23 with FZ_Shift; use FZ_Shift;
ffa_ch11_tuning_a...   24 
ffa_ch11_tuning_a...   25 
ffa_ch11_tuning_a...   26 package body FZ_IO is
ffa_ch11_tuning_a...   27    
ffa_ch11_tuning_a...   28    -- Expand FZ N by nibble D, and determine whether this operation overflowed
ffa_ch11_tuning_a...   29    procedure FZ_Insert_Bottom_Nibble(N        : in out FZ;
ffa_ch11_tuning_a...   30                                      D        : in     Nibble;
ffa_ch11_tuning_a...   31                                      Overflow : out    WBool) is
ffa_ch11_tuning_a...   32       
ffa_ch11_tuning_a...   33       -- The overflow, if any, from shifting N in-place leftward by 4 bits
ffa_ch11_tuning_a...   34       Shifted_N_Overflow : Word := 0;
ffa_ch11_tuning_a...   35       
ffa_ch11_tuning_a...   36    begin
ffa_ch11_tuning_a...   37       -- Make room in N for one additional hex digit (i.e. multiply N by 16)
ffa_ch11_tuning_a...   38       FZ_ShiftLeft_O(N        => N,
ffa_ch11_tuning_a...   39                      ShiftedN => N,
ffa_ch11_tuning_a...   40                      Count    => 4,
ffa_ch11_tuning_a...   41                      Overflow => Shifted_N_Overflow);
ffa_ch11_tuning_a...   42       
ffa_ch11_tuning_a...   43       -- Place the new digit into the now-vacated four bits at the bottom of N.
ffa_ch11_tuning_a...   44       FZ_Or_W(N, D);
ffa_ch11_tuning_a...   45       
ffa_ch11_tuning_a...   46       -- Record whether the above operation overflowed N:
ffa_ch11_tuning_a...   47       Overflow := W_NZeroP(Shifted_N_Overflow);
ffa_ch11_tuning_a...   48       
ffa_ch11_tuning_a...   49    end FZ_Insert_Bottom_Nibble;
ffa_ch11_tuning_a...   50    
ffa_ch11_tuning_a...   51       
ffa_ch11_tuning_a...   52    -- Determine the number of ASCII characters required to represent N
ffa_ch11_tuning_a...   53    function FZ_ASCII_Length(N : in FZ) return Char_Count is
ffa_ch11_tuning_a...   54    begin
ffa_ch11_tuning_a...   55       return N'Length * Nibbleness;
ffa_ch11_tuning_a...   56    end FZ_ASCII_Length;
ffa_ch11_tuning_a...   57    
ffa_ch11_tuning_a...   58    
ffa_ch11_tuning_a...   59    -- Write an ASCII hex representation of N into existing string buffer S
ffa_ch11_tuning_a...   60    procedure FZ_To_Hex_String(N : in FZ; S : out String) is
ffa_ch11_tuning_a...   61       
ffa_ch11_tuning_a...   62       -- Indices into the string S (note, String always indexes from 1)
ffa_ch11_tuning_a...   63       subtype SiRange is Natural range S'First .. S'Last;
ffa_ch11_tuning_a...   64       
ffa_ch11_tuning_a...   65       -- Position of current character in S being written
ffa_ch11_tuning_a...   66       Si : SiRange; -- Walks from 1 to the string length of S
ffa_ch11_tuning_a...   67       
ffa_ch11_tuning_a...   68    begin
ffa_ch11_tuning_a...   69       
ffa_ch11_tuning_a...   70       -- Step through all indices of N, regardless of how it was indexed:
ffa_ch11_tuning_a...   71       for i in 0 .. Word_Index(N'Length - 1) loop
ffa_ch11_tuning_a...   72          declare
ffa_ch11_tuning_a...   73             
ffa_ch11_tuning_a...   74             -- Index of current Word, walks from ~top~ Word of N to ~bottom~
ffa_ch11_tuning_a...   75             Wi : constant Word_Index := N'Last - i;
ffa_ch11_tuning_a...   76             
ffa_ch11_tuning_a...   77             -- Currently-selected Word of N
ffa_ch11_tuning_a...   78             W  : Word := N(Wi);
ffa_ch11_tuning_a...   79             
ffa_ch11_tuning_a...   80          begin
ffa_ch11_tuning_a...   81             
ffa_ch11_tuning_a...   82             -- For each nibble in the Word:
ffa_ch11_tuning_a...   83             for j in 1 .. Nibbleness loop
ffa_ch11_tuning_a...   84                
ffa_ch11_tuning_a...   85                -- Current position in S that is to be written
ffa_ch11_tuning_a...   86                Si    := (Natural(i) * Nibbleness) + j;
ffa_ch11_tuning_a...   87                
ffa_ch11_tuning_a...   88                -- Rotate the top nibble of W into the bottom nibble.
ffa_ch11_tuning_a...   89                W     := Rotate_Left(W, 4);
ffa_ch11_tuning_a...   90                
ffa_ch11_tuning_a...   91                -- Write the ASCII representation of the bottom nibble.
ffa_ch11_tuning_a...   92                S(Si) := HexDigs(Natural(W and 16#F#));
ffa_ch11_tuning_a...   93                
ffa_ch11_tuning_a...   94             end loop;
ffa_ch11_tuning_a...   95             
ffa_ch11_tuning_a...   96             -- Barring cosmic ray, W will have rotated to its initial value
ffa_ch11_tuning_a...   97             pragma Assert(W = N(Wi));
ffa_ch11_tuning_a...   98             
ffa_ch11_tuning_a...   99          end;
ffa_ch11_tuning_a...  100          
ffa_ch11_tuning_a...  101       end loop;
ffa_ch11_tuning_a...  102       
ffa_ch11_tuning_a...  103       -- Barring cosmic ray, the last char written was to the final pos in S,
ffa_ch11_tuning_a...  104       pragma Assert(Si = SiRange'Last); -- as S is mandatorily exactly-sized.
ffa_ch11_tuning_a...  105       
ffa_ch11_tuning_a...  106    end FZ_To_Hex_String;
ffa_ch11_tuning_a...  107    
ffa_ch11_tuning_a...  108 end FZ_IO;