File : fz_shift.adb
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 W_Shifts; use W_Shifts;
21
22
23 package body FZ_Shift is
24
25 --------------------------------------------------------------
26 -- Shift Right
27 --------------------------------------------------------------
28
29 -- ShiftedN := N >> Count (with Overflow Input and Output)
30 -- WARNING: OF_in MUST be of valid bit-width for the shift!
31 procedure FZ_ShiftRight_O_I(N : in FZ;
32 ShiftedN : out FZ;
33 Count : in WBit_Index;
34 Overflow : out Word;
35 OF_in : in Word) is
36 Ni : Word;
37 Carry : Word := OF_in;
38 begin
39 for i in reverse N'Range loop
40 Ni := N(i);
41 ShiftedN(i) := Shift_Right(Ni, Count) or Carry;
42 Carry := Shift_Left(Ni, Bitness - Count);
43 end loop;
44 Overflow := Carry;
45 end FZ_ShiftRight_O_I;
46
47
48 -- ShiftedN := N >> Count (with Overflow Output only)
49 procedure FZ_ShiftRight_O(N : in FZ;
50 ShiftedN : out FZ;
51 Count : in WBit_Index;
52 Overflow : out Word) is
53 begin
54 FZ_ShiftRight_O_I(N, ShiftedN, Count, Overflow, 0);
55 end FZ_ShiftRight_O;
56
57
58 -- ShiftedN := N >> Count (no Overflow output or input)
59 procedure FZ_ShiftRight(N : in FZ;
60 ShiftedN : out FZ;
61 Count : in WBit_Index) is
62 Overflow : Word;
63 pragma Unreferenced(Overflow);
64 begin
65 FZ_ShiftRight_O_I(N, ShiftedN, Count, Overflow, 0);
66 end FZ_ShiftRight;
67
68 --------------------------------------------------------------
69 -- Shift Left
70 --------------------------------------------------------------
71
72 -- ShiftedN := N << Count (with Overflow Input and Output)
73 -- WARNING: OF_in MUST be of valid bit-width for the shift!
74 procedure FZ_ShiftLeft_O_I(N : in FZ;
75 ShiftedN : out FZ;
76 Count : in WBit_Index;
77 Overflow : out Word;
78 OF_in : in Word) is
79 Ni : Word;
80 Carry : Word := OF_in;
81 begin
82 for i in N'Range loop
83 Ni := N(i);
84 ShiftedN(i) := Shift_Left(Ni, Count) or Carry;
85 Carry := Shift_Right(Ni, Bitness - Count);
86 end loop;
87 Overflow := Carry;
88 end FZ_ShiftLeft_O_I;
89
90
91 -- ShiftedN := N << Count (with Overflow Output only)
92 procedure FZ_ShiftLeft_O(N : in FZ;
93 ShiftedN : out FZ;
94 Count : in WBit_Index;
95 Overflow : out Word) is
96 begin
97 FZ_ShiftLeft_O_I(N, ShiftedN, Count, Overflow, 0);
98 end FZ_ShiftLeft_O;
99
100
101 -- ShiftedN := N << Count (no Overflow output or input)
102 procedure FZ_ShiftLeft(N : in FZ;
103 ShiftedN : out FZ;
104 Count : in WBit_Index) is
105 Overflow : Word;
106 pragma Unreferenced(Overflow);
107 begin
108 FZ_ShiftLeft_O_I(N, ShiftedN, Count, Overflow, 0);
109 end FZ_ShiftLeft;
110
111 end FZ_Shift;