File : fz_basic.adb

   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 --                                                                          --
  16 -- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     --
  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);
  47       FZ_Set_Head(N, V);
  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;
  55    end FZ_Set_Head;
  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);
  62    end FZ_Get_Head;
  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;