```   1 ------------------------------------------------------------------------------
2 ------------------------------------------------------------------------------
3 -- This file is part of 'Finite Field Arithmetic', aka 'FFA'.               --
4 --                                                                          --
5 -- (C) 2017 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 Word_Ops; use Word_Ops;
21
22
23 package body FZ_Basic is
24
25    ---------------------------------------------------------------------------
26    -- Fundamental Operations on FZ (finite integers)
27    ---------------------------------------------------------------------------
28
29    -- Determine the Bitness of N
30    function FZ_Bitness(N : in FZ) return Bit_Count is
31    begin
32       return N'Length * Words.Bitness;
33    end FZ_Bitness;
34
35
36    -- N := 0
37    procedure FZ_Clear(N : out FZ) is
38    begin
39       N := (others => 0);
40    end FZ_Clear;
41
42
43    -- Set given FZ to a given truth value
44    procedure WBool_To_FZ(V : in WBool; N : out FZ) is
45    begin
46       FZ_Clear(N);
48    end WBool_To_FZ;
49
50
51    -- First word of N := Source
52    procedure FZ_Set_Head(N : out FZ; Source : in Word) is
53    begin
54       N(N'First) := Source;
56
57
58    -- First word of N
59    function FZ_Get_Head(N : in FZ) return Word is
60    begin
61       return N(N'First);
63
64
65    -- Exchange X and Y
66    procedure FZ_Swap(X : in out FZ; Y : in out FZ) is
67       T : FZ(X'Range);
68    begin
69       T := X;
70       X := Y;
71       Y := T;
72    end FZ_Swap;
73
74
75    -- Constant-time MUX: Sel = 0: Result := X; Sel = 1: Result := Y
76    procedure FZ_Mux(X : in FZ; Y : in FZ; Result : out FZ; Sel : in WBool) is
77    begin
78       for i in X'Range loop
79          Result(i) := W_Mux(X(i), Y(i), Sel);
80       end loop;
81    end FZ_Mux;
82
83 end FZ_Basic;
```