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