```   1 ------------------------------------------------------------------------------
2 ------------------------------------------------------------------------------
3 -- This file is part of 'Finite Field Arithmetic', aka 'FFA'.               --
4 --                                                                          --
5 -- (C) 2018 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 --                                                                          --
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;
```