gcc/ada/s-pack23.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . P A C K _ 2 3                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2005, 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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 with System.Storage_Elements;
  35 with System.Unsigned_Types;
  36 with Unchecked_Conversion;
  37
  38 package body System.Pack_23 is
  39
  40    subtype Ofs is System.Storage_Elements.Storage_Offset;
  41    subtype Uns is System.Unsigned_Types.Unsigned;
  42    subtype N07 is System.Unsigned_Types.Unsigned range 0 .. 7;
  43
  44    use type System.Storage_Elements.Storage_Offset;
  45    use type System.Unsigned_Types.Unsigned;
  46
  47    type Cluster is record
  48       E0, E1, E2, E3, E4, E5, E6, E7 : Bits_23;
  49    end record;
  50
  51    for Cluster use record
  52       E0 at 0 range 0 * Bits .. 0 * Bits + Bits - 1;
  53       E1 at 0 range 1 * Bits .. 1 * Bits + Bits - 1;
  54       E2 at 0 range 2 * Bits .. 2 * Bits + Bits - 1;
  55       E3 at 0 range 3 * Bits .. 3 * Bits + Bits - 1;
  56       E4 at 0 range 4 * Bits .. 4 * Bits + Bits - 1;
  57       E5 at 0 range 5 * Bits .. 5 * Bits + Bits - 1;
  58       E6 at 0 range 6 * Bits .. 6 * Bits + Bits - 1;
  59       E7 at 0 range 7 * Bits .. 7 * Bits + Bits - 1;
  60    end record;
  61
  62    for Cluster'Size use Bits * 8;
  63
  64    for Cluster'Alignment use Integer'Min (Standard'Maximum_Alignment,
  65      1 +
  66      1 * Boolean'Pos (Bits mod 2 = 0) +
  67      2 * Boolean'Pos (Bits mod 4 = 0));
  68    --  Use maximum possible alignment, given the bit field size, since this
  69    --  will result in the most efficient code possible for the field.
  70
  71    type Cluster_Ref is access Cluster;
  72
  73    function To_Ref is new
  74      Unchecked_Conversion (System.Address, Cluster_Ref);
  75
  76    ------------
  77    -- Get_23 --
  78    ------------
  79
  80    function Get_23 (Arr : System.Address; N : Natural) return Bits_23 is
  81       C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
  82    begin
  83       case N07 (Uns (N) mod 8) is
  84          when 0 => return C.E0;
  85          when 1 => return C.E1;
  86          when 2 => return C.E2;
  87          when 3 => return C.E3;
  88          when 4 => return C.E4;
  89          when 5 => return C.E5;
  90          when 6 => return C.E6;
  91          when 7 => return C.E7;
  92       end case;
  93    end Get_23;
  94
  95    ------------
  96    -- Set_23 --
  97    ------------
  98
  99    procedure Set_23 (Arr : System.Address; N : Natural; E : Bits_23) is
 100       C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
 101    begin
 102       case N07 (Uns (N) mod 8) is
 103          when 0 => C.E0 := E;
 104          when 1 => C.E1 := E;
 105          when 2 => C.E2 := E;
 106          when 3 => C.E3 := E;
 107          when 4 => C.E4 := E;
 108          when 5 => C.E5 := E;
 109          when 6 => C.E6 := E;
 110          when 7 => C.E7 := E;
 111       end case;
 112    end Set_23;
 113
 114 end System.Pack_23;