gcc/ada/s-pack17.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUNTIME COMPONENTS                          --
   4 --                                                                          --
   5 --                       S Y S T E M . P A C K _ 1 7                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                                                                          --
  10 --          Copyright (C) 1992-1999 Free Software Foundation, Inc.          --
  11 --                                                                          --
  12 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  20 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNAT was originally developed  by the GNAT team at  New York University. --
  31 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  32 --                                                                          --
  33 ------------------------------------------------------------------------------
  34
  35 with System.Storage_Elements;
  36 with System.Unsigned_Types;
  37 with Unchecked_Conversion;
  38
  39 package body System.Pack_17 is
  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_17;
  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    function To_Ref is new
  75      Unchecked_Conversion (System.Address, Cluster_Ref);
  76
  77    ------------
  78    -- Get_17 --
  79    ------------
  80
  81    function Get_17 (Arr : System.Address; N : Natural) return Bits_17 is
  82       C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
  83
  84    begin
  85       case N07 (Uns (N) mod 8) is
  86          when 0 => return C.E0;
  87          when 1 => return C.E1;
  88          when 2 => return C.E2;
  89          when 3 => return C.E3;
  90          when 4 => return C.E4;
  91          when 5 => return C.E5;
  92          when 6 => return C.E6;
  93          when 7 => return C.E7;
  94       end case;
  95    end Get_17;
  96
  97    ------------
  98    -- Set_17 --
  99    ------------
 100
 101    procedure Set_17 (Arr : System.Address; N : Natural; E : Bits_17) is
 102       C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
 103
 104    begin
 105       case N07 (Uns (N) mod 8) is
 106          when 0 => C.E0 := E;
 107          when 1 => C.E1 := E;
 108          when 2 => C.E2 := E;
 109          when 3 => C.E3 := E;
 110          when 4 => C.E4 := E;
 111          when 5 => C.E5 := E;
 112          when 6 => C.E6 := E;
 113          when 7 => C.E7 := E;
 114       end case;
 115    end Set_17;
 116
 117 end System.Pack_17;