gcc/ada/s-pack20.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . P A C K _ 2 0                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2009, 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 with System.Storage_Elements;
  33 with System.Unsigned_Types;
  34 with Ada.Unchecked_Conversion;
  35
  36 package body System.Pack_20 is
  37
  38    subtype Ofs is System.Storage_Elements.Storage_Offset;
  39    subtype Uns is System.Unsigned_Types.Unsigned;
  40    subtype N07 is System.Unsigned_Types.Unsigned range 0 .. 7;
  41
  42    use type System.Storage_Elements.Storage_Offset;
  43    use type System.Unsigned_Types.Unsigned;
  44
  45    type Cluster is record
  46       E0, E1, E2, E3, E4, E5, E6, E7 : Bits_20;
  47    end record;
  48
  49    for Cluster use record
  50       E0 at 0 range 0 * Bits .. 0 * Bits + Bits - 1;
  51       E1 at 0 range 1 * Bits .. 1 * Bits + Bits - 1;
  52       E2 at 0 range 2 * Bits .. 2 * Bits + Bits - 1;
  53       E3 at 0 range 3 * Bits .. 3 * Bits + Bits - 1;
  54       E4 at 0 range 4 * Bits .. 4 * Bits + Bits - 1;
  55       E5 at 0 range 5 * Bits .. 5 * Bits + Bits - 1;
  56       E6 at 0 range 6 * Bits .. 6 * Bits + Bits - 1;
  57       E7 at 0 range 7 * Bits .. 7 * Bits + Bits - 1;
  58    end record;
  59
  60    for Cluster'Size use Bits * 8;
  61
  62    for Cluster'Alignment use Integer'Min (Standard'Maximum_Alignment,
  63      1 +
  64      1 * Boolean'Pos (Bits mod 2 = 0) +
  65      2 * Boolean'Pos (Bits mod 4 = 0));
  66    --  Use maximum possible alignment, given the bit field size, since this
  67    --  will result in the most efficient code possible for the field.
  68
  69    type Cluster_Ref is access Cluster;
  70
  71    function To_Ref is new
  72      Ada.Unchecked_Conversion (System.Address, Cluster_Ref);
  73
  74    --  The following declarations are for the case where the address
  75    --  passed to GetU_20 or SetU_20 is not guaranteed to be aligned.
  76    --  These routines are used when the packed array is itself a
  77    --  component of a packed record, and therefore may not be aligned.
  78
  79    type ClusterU is new Cluster;
  80    for ClusterU'Alignment use 1;
  81
  82    type ClusterU_Ref is access ClusterU;
  83
  84    function To_Ref is new
  85      Ada.Unchecked_Conversion (System.Address, ClusterU_Ref);
  86
  87    ------------
  88    -- Get_20 --
  89    ------------
  90
  91    function Get_20 (Arr : System.Address; N : Natural) return Bits_20 is
  92       C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
  93    begin
  94       case N07 (Uns (N) mod 8) is
  95          when 0 => return C.E0;
  96          when 1 => return C.E1;
  97          when 2 => return C.E2;
  98          when 3 => return C.E3;
  99          when 4 => return C.E4;
 100          when 5 => return C.E5;
 101          when 6 => return C.E6;
 102          when 7 => return C.E7;
 103       end case;
 104    end Get_20;
 105
 106    -------------
 107    -- GetU_20 --
 108    -------------
 109
 110    function GetU_20 (Arr : System.Address; N : Natural) return Bits_20 is
 111       C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
 112    begin
 113       case N07 (Uns (N) mod 8) is
 114          when 0 => return C.E0;
 115          when 1 => return C.E1;
 116          when 2 => return C.E2;
 117          when 3 => return C.E3;
 118          when 4 => return C.E4;
 119          when 5 => return C.E5;
 120          when 6 => return C.E6;
 121          when 7 => return C.E7;
 122       end case;
 123    end GetU_20;
 124
 125    ------------
 126    -- Set_20 --
 127    ------------
 128
 129    procedure Set_20 (Arr : System.Address; N : Natural; E : Bits_20) is
 130       C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
 131    begin
 132       case N07 (Uns (N) mod 8) is
 133          when 0 => C.E0 := E;
 134          when 1 => C.E1 := E;
 135          when 2 => C.E2 := E;
 136          when 3 => C.E3 := E;
 137          when 4 => C.E4 := E;
 138          when 5 => C.E5 := E;
 139          when 6 => C.E6 := E;
 140          when 7 => C.E7 := E;
 141       end case;
 142    end Set_20;
 143
 144    -------------
 145    -- SetU_20 --
 146    -------------
 147
 148    procedure SetU_20 (Arr : System.Address; N : Natural; E : Bits_20) is
 149       C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
 150    begin
 151       case N07 (Uns (N) mod 8) is
 152          when 0 => C.E0 := E;
 153          when 1 => C.E1 := E;
 154          when 2 => C.E2 := E;
 155          when 3 => C.E3 := E;
 156          when 4 => C.E4 := E;
 157          when 5 => C.E5 := E;
 158          when 6 => C.E6 := E;
 159          when 7 => C.E7 := E;
 160       end case;
 161    end SetU_20;
 162
 163 end System.Pack_20;