1------------------------------------------------------------------------------
2--                                                                          --
3--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
4--                                                                          --
5--     S Y S T E M . V E C T O R S . B O O L E A N _ O P E R A T I O N S    --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--          Copyright (C) 2002-2018, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32package body System.Vectors.Boolean_Operations is
33
34   SU : constant := Storage_Unit;
35   --  Convenient short hand, used throughout
36
37   --  The coding of this unit depends on the fact that the Component_Size
38   --  of a normally declared array of Boolean is equal to Storage_Unit. We
39   --  can't use the Component_Size directly since it is non-static. The
40   --  following declaration checks that this declaration is correct
41
42   type Boolean_Array is array (Integer range <>) of Boolean;
43   pragma Compile_Time_Error
44     (Boolean_Array'Component_Size /= SU, "run time compile failure");
45
46   --  NOTE: The boolean literals must be qualified here to avoid visibility
47   --  anomalies when this package is compiled through Rtsfind, in a context
48   --  that includes a user-defined type derived from boolean.
49
50   True_Val : constant Vector := Standard.True'Enum_Rep
51                                   + Standard.True'Enum_Rep * 2**SU
52                                   + Standard.True'Enum_Rep * 2**(SU * 2)
53                                   + Standard.True'Enum_Rep * 2**(SU * 3)
54                                   + Standard.True'Enum_Rep * 2**(SU * 4)
55                                   + Standard.True'Enum_Rep * 2**(SU * 5)
56                                   + Standard.True'Enum_Rep * 2**(SU * 6)
57                                   + Standard.True'Enum_Rep * 2**(SU * 7);
58   --  This constant represents the bits to be flipped to perform a logical
59   --  "not" on a vector of booleans, independent of the actual
60   --  representation of True.
61
62   --  The representations of (False, True) are assumed to be zero/one and
63   --  the maximum number of unpacked booleans per Vector is assumed to be 8.
64
65   pragma Assert (Standard.False'Enum_Rep = 0);
66   pragma Assert (Standard.True'Enum_Rep = 1);
67   pragma Assert (Vector'Size / Storage_Unit <= 8);
68
69   --  The reason we need to do these gymnastics is that no call to
70   --  Unchecked_Conversion can be made at the library level since this
71   --  unit is pure. Also a conversion from the array type to the Vector type
72   --  inside the body of "not" is inefficient because of alignment issues.
73
74   -----------
75   -- "not" --
76   -----------
77
78   function "not" (Item : Vectors.Vector) return Vectors.Vector is
79   begin
80      return Item xor True_Val;
81   end "not";
82
83   ----------
84   -- Nand --
85   ----------
86
87   function Nand (Left, Right : Boolean) return Boolean is
88   begin
89      return not (Left and Right);
90   end Nand;
91
92   function Nand (Left, Right : Vectors.Vector) return Vectors.Vector is
93   begin
94      return not (Left and Right);
95   end Nand;
96
97   ---------
98   -- Nor --
99   ---------
100
101   function Nor (Left, Right : Boolean) return Boolean is
102   begin
103      return not (Left or Right);
104   end Nor;
105
106   function Nor (Left, Right : Vectors.Vector) return Vectors.Vector is
107   begin
108      return not (Left or Right);
109   end Nor;
110
111   ----------
112   -- Nxor --
113   ----------
114
115   function Nxor (Left, Right : Boolean) return Boolean is
116   begin
117      return not (Left xor Right);
118   end Nxor;
119
120   function Nxor (Left, Right : Vectors.Vector) return Vectors.Vector is
121   begin
122      return not (Left xor Right);
123   end Nxor;
124
125end System.Vectors.Boolean_Operations;
126