gcc/ada/s-pack21.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . P A C K _ 2 1                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2014, 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
  35 package body System.Pack_21 is
  36
  37    subtype Bit_Order is System.Bit_Order;
  38    Reverse_Bit_Order : constant Bit_Order :=
  39      Bit_Order'Val (1 - Bit_Order'Pos (System.Default_Bit_Order));
  40
  41    subtype Ofs is System.Storage_Elements.Storage_Offset;
  42    subtype Uns is System.Unsigned_Types.Unsigned;
  43    subtype N07 is System.Unsigned_Types.Unsigned range 0 .. 7;
  44
  45    use type System.Storage_Elements.Storage_Offset;
  46    use type System.Unsigned_Types.Unsigned;
  47
  48    type Cluster is record
  49       E0, E1, E2, E3, E4, E5, E6, E7 : Bits_21;
  50    end record;
  51
  52    for Cluster use record
  53       E0 at 0 range 0 * Bits .. 0 * Bits + Bits - 1;
  54       E1 at 0 range 1 * Bits .. 1 * Bits + Bits - 1;
  55       E2 at 0 range 2 * Bits .. 2 * Bits + Bits - 1;
  56       E3 at 0 range 3 * Bits .. 3 * Bits + Bits - 1;
  57       E4 at 0 range 4 * Bits .. 4 * Bits + Bits - 1;
  58       E5 at 0 range 5 * Bits .. 5 * Bits + Bits - 1;
  59       E6 at 0 range 6 * Bits .. 6 * Bits + Bits - 1;
  60       E7 at 0 range 7 * Bits .. 7 * Bits + Bits - 1;
  61    end record;
  62
  63    for Cluster'Size use Bits * 8;
  64
  65    for Cluster'Alignment use Integer'Min (Standard'Maximum_Alignment,
  66      1 +
  67      1 * Boolean'Pos (Bits mod 2 = 0) +
  68      2 * Boolean'Pos (Bits mod 4 = 0));
  69    --  Use maximum possible alignment, given the bit field size, since this
  70    --  will result in the most efficient code possible for the field.
  71
  72    type Cluster_Ref is access Cluster;
  73
  74    type Rev_Cluster is new Cluster
  75      with Bit_Order            => Reverse_Bit_Order,
  76           Scalar_Storage_Order => Reverse_Bit_Order;
  77    type Rev_Cluster_Ref is access Rev_Cluster;
  78
  79    ------------
  80    -- Get_21 --
  81    ------------
  82
  83    function Get_21
  84      (Arr     : System.Address;
  85       N       : Natural;
  86       Rev_SSO : Boolean) return Bits_21
  87    is
  88       A  : constant System.Address := Arr + Bits * Ofs (Uns (N) / 8);
  89       C  : Cluster_Ref     with Address => A'Address, Import;
  90       RC : Rev_Cluster_Ref with Address => A'Address, Import;
  91    begin
  92       if Rev_SSO then
  93          case N07 (Uns (N) mod 8) is
  94             when 0 => return RC.E0;
  95             when 1 => return RC.E1;
  96             when 2 => return RC.E2;
  97             when 3 => return RC.E3;
  98             when 4 => return RC.E4;
  99             when 5 => return RC.E5;
 100             when 6 => return RC.E6;
 101             when 7 => return RC.E7;
 102          end case;
 103
 104       else
 105          case N07 (Uns (N) mod 8) is
 106             when 0 => return C.E0;
 107             when 1 => return C.E1;
 108             when 2 => return C.E2;
 109             when 3 => return C.E3;
 110             when 4 => return C.E4;
 111             when 5 => return C.E5;
 112             when 6 => return C.E6;
 113             when 7 => return C.E7;
 114          end case;
 115       end if;
 116    end Get_21;
 117
 118    ------------
 119    -- Set_21 --
 120    ------------
 121
 122    procedure Set_21
 123      (Arr     : System.Address;
 124       N       : Natural;
 125       E       : Bits_21;
 126       Rev_SSO : Boolean)
 127    is
 128       A  : constant System.Address := Arr + Bits * Ofs (Uns (N) / 8);
 129       C  : Cluster_Ref     with Address => A'Address, Import;
 130       RC : Rev_Cluster_Ref with Address => A'Address, Import;
 131    begin
 132       if Rev_SSO then
 133          case N07 (Uns (N) mod 8) is
 134             when 0 => RC.E0 := E;
 135             when 1 => RC.E1 := E;
 136             when 2 => RC.E2 := E;
 137             when 3 => RC.E3 := E;
 138             when 4 => RC.E4 := E;
 139             when 5 => RC.E5 := E;
 140             when 6 => RC.E6 := E;
 141             when 7 => RC.E7 := E;
 142          end case;
 143       else
 144          case N07 (Uns (N) mod 8) is
 145             when 0 => C.E0 := E;
 146             when 1 => C.E1 := E;
 147             when 2 => C.E2 := E;
 148             when 3 => C.E3 := E;
 149             when 4 => C.E4 := E;
 150             when 5 => C.E5 := E;
 151             when 6 => C.E6 := E;
 152             when 7 => C.E7 := E;
 153          end case;
 154       end if;
 155    end Set_21;
 156
 157 end System.Pack_21;