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