File : fz_lomul.ads
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 FZ_Type; use FZ_Type;
21
22
23 -- "Low Multiplication" computes only the bottom half of the product XY.
24 -- Presently, it is used solely in Barrett's Modular Reduction.
25
26 package FZ_LoMul is
27
28 pragma Pure;
29
30 -- Threshhold for Low Mul - at or below this many Words, we use Comba mult.
31 Low_Mul_Thresh : constant Indices := 8;
32
33 -- Multiply. (CAUTION: UNBUFFERED)
34 procedure FZ_Low_Multiply_Unbuffered(X : in FZ;
35 Y : in FZ;
36 XY : out FZ);
37 pragma Inline_Always(FZ_Low_Multiply_Unbuffered);
38
39 -- Comba's multiplier. (CAUTION: UNBUFFERED)
40 procedure FZ_Low_Mul_Comba(X : in FZ;
41 Y : in FZ;
42 XY : out FZ);
43 pragma Inline_Always(FZ_Low_Mul_Comba);
44
45 -- Low Multiplier. (CAUTION: UNBUFFERED)
46 procedure Low_Mul(X : in FZ;
47 Y : in FZ;
48 XY : out FZ)
49 with Pre => X'Length = Y'Length and
50 XY'Length = X'Length and
51 X'Length mod 2 = 0;
52 -- CAUTION: Inlining prohibited for Low_Mul !
53
54 -- Low-Only Multiplier. Preserves the inputs.
55 procedure FZ_Low_Multiply_Buffered(X : in FZ;
56 Y : in FZ;
57 XY : out FZ)
58 with Pre => X'Length = Y'Length and
59 XY'Length = X'Length and
60 X'Length mod 2 = 0;
61
62 end FZ_LoMul;