------------------------------------------------------------------------------
------------------------------------------------------------------------------
-- This file is part of 'Finite Field Arithmetic', aka 'FFA'.               --
--                                                                          --
-- (C) 2017 Stanislav Datskovskiy ( www.loper-os.org )                      --
-- http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     --
--                                                                          --
-- You do not have, nor can you ever acquire the right to use, copy or      --
-- distribute this software ; Should you use this software for any purpose, --
-- or copy and distribute it to anyone or in any manner, you are breaking   --
-- the laws of whatever soi-disant jurisdiction, and you promise to         --
-- continue doing so for the indefinite future. In any case, please         --
-- always : read and understand any software ; verify any PGP signatures    --
-- that you use - for any purpose.                                          --
--                                                                          --
-- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     --
------------------------------------------------------------------------------
------------------------------------------------------------------------------

with Words;   use Words;
with FZ_Type; use FZ_Type;


-- Fundamental Arithmetic operators on FZ:
package FZ_Arith is
   
   pragma Pure;
   
   -- Destructive Add: X := X + Y; Overflow := Carry; optional OF_In
   procedure FZ_Add_D(X          : in out FZ;
                      Y          : in     FZ;
                      Overflow   : out    WBool;
                      OF_In      : in     WBool := 0);
   pragma Precondition(X'Length = Y'Length);
   
      -- Destructive Add: X := X + W; Overflow := Carry
   procedure FZ_Add_D_W(X        : in out FZ;
                        W        : in     Word;
                        Overflow : out    WBool);
   
   -- Sum := X + Y; Overflow := Carry
   procedure FZ_Add(X          : in    FZ;
                    Y          : in    FZ;
                    Sum        : out   FZ;
                    Overflow   : out   WBool);
   pragma Precondition(X'Length = Y'Length and X'Length = Sum'Length);
   
   -- Gate = 1: Sum := X + Y; Overflow := Carry
   -- Gate = 0: Sum := X;     Overflow := 0
   procedure FZ_Add_Gated_O(X          : in  FZ;
                            Y          : in  FZ;
                            Gate       : in  WBool;
                            Sum        : out FZ;
                            Overflow   : out WBool);
   pragma Precondition(X'Length = Y'Length and X'Length = Sum'Length);
   
   -- Same as FZ_Add_Gated_O, but without Overflow output
   procedure FZ_Add_Gated(X          : in  FZ;
                          Y          : in  FZ;
                          Gate       : in  WBool;
                          Sum        : out FZ);
   pragma Precondition(X'Length = Y'Length and X'Length = Sum'Length);
   
   -- Difference := X - Y; Underflow := Borrow
   procedure FZ_Sub(X          : in  FZ;
                    Y          : in  FZ;
                    Difference : out FZ;
                    Underflow  : out WBool);
   pragma Precondition(X'Length = Y'Length and X'Length = Difference'Length);
   
   -- Destructive: If Cond is 1, NotN := ~N; otherwise NotN := N.
   procedure FZ_Not_Cond_D(N    : in out FZ;
                           Cond : in     WBool);
   
   -- Subtractor that gets absolute value if underflowed, in const. time
   procedure FZ_Sub_Abs(X          : in FZ;
                        Y          : in FZ;
                        Difference : out FZ;
                        Underflow  : out WBool);
   pragma Precondition(X'Length = Y'Length and X'Length = Difference'Length);
   
end FZ_Arith;