gcc/ada/libgnat/s-veboop.adb

   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
  32 package 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
 125 end System.Vectors.Boolean_Operations;