gcc/ada/s-pack12.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUNTIME COMPONENTS                          --
   4 --                                                                          --
   5 --                       S Y S T E M . P A C K _ 1 2                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                            $Revision: 1.4 $
  10 --                                                                          --
  11 --          Copyright (C) 1992-1999 Free Software Foundation, Inc.          --
  12 --                                                                          --
  13 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  14 -- terms of the  GNU General Public License as published  by the Free Soft- --
  15 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  16 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  17 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  18 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  19 -- for  more details.  You should have  received  a copy of the GNU General --
  20 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  21 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  22 -- MA 02111-1307, USA.                                                      --
  23 --                                                                          --
  24 -- As a special exception,  if other files  instantiate  generics from this --
  25 -- unit, or you link  this unit with other files  to produce an executable, --
  26 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  27 -- covered  by the  GNU  General  Public  License.  This exception does not --
  28 -- however invalidate  any other reasons why  the executable file  might be --
  29 -- covered by the  GNU Public License.                                      --
  30 --                                                                          --
  31 -- GNAT was originally developed  by the GNAT team at  New York University. --
  32 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  33 --                                                                          --
  34 ------------------------------------------------------------------------------
  35
  36 with System.Storage_Elements;
  37 with System.Unsigned_Types;
  38 with Unchecked_Conversion;
  39
  40 package body System.Pack_12 is
  41
  42    subtype Ofs is System.Storage_Elements.Storage_Offset;
  43    subtype Uns is System.Unsigned_Types.Unsigned;
  44    subtype N07 is System.Unsigned_Types.Unsigned range 0 .. 7;
  45
  46    use type System.Storage_Elements.Storage_Offset;
  47    use type System.Unsigned_Types.Unsigned;
  48
  49    type Cluster is record
  50       E0, E1, E2, E3, E4, E5, E6, E7 : Bits_12;
  51    end record;
  52
  53    for Cluster use record
  54       E0 at 0 range 0 * Bits .. 0 * Bits + Bits - 1;
  55       E1 at 0 range 1 * Bits .. 1 * Bits + Bits - 1;
  56       E2 at 0 range 2 * Bits .. 2 * Bits + Bits - 1;
  57       E3 at 0 range 3 * Bits .. 3 * Bits + Bits - 1;
  58       E4 at 0 range 4 * Bits .. 4 * Bits + Bits - 1;
  59       E5 at 0 range 5 * Bits .. 5 * Bits + Bits - 1;
  60       E6 at 0 range 6 * Bits .. 6 * Bits + Bits - 1;
  61       E7 at 0 range 7 * Bits .. 7 * Bits + Bits - 1;
  62    end record;
  63
  64    for Cluster'Size use Bits * 8;
  65
  66    for Cluster'Alignment use Integer'Min (Standard'Maximum_Alignment,
  67      1 +
  68      1 * Boolean'Pos (Bits mod 2 = 0) +
  69      2 * Boolean'Pos (Bits mod 4 = 0));
  70    --  Use maximum possible alignment, given the bit field size, since this
  71    --  will result in the most efficient code possible for the field.
  72
  73    type Cluster_Ref is access Cluster;
  74
  75    function To_Ref is new
  76      Unchecked_Conversion (System.Address, Cluster_Ref);
  77
  78    --  The following declarations are for the case where the address
  79    --  passed to GetU_12 or SetU_12 is not guaranteed to be aligned.
  80    --  These routines are used when the packed array is itself a
  81    --  component of a packed record, and therefore may not be aligned.
  82
  83    type ClusterU is new Cluster;
  84    for ClusterU'Alignment use 1;
  85
  86    type ClusterU_Ref is access ClusterU;
  87
  88    function To_Ref is new
  89      Unchecked_Conversion (System.Address, ClusterU_Ref);
  90
  91    ------------
  92    -- Get_12 --
  93    ------------
  94
  95    function Get_12 (Arr : System.Address; N : Natural) return Bits_12 is
  96       C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
  97
  98    begin
  99       case N07 (Uns (N) mod 8) is
 100          when 0 => return C.E0;
 101          when 1 => return C.E1;
 102          when 2 => return C.E2;
 103          when 3 => return C.E3;
 104          when 4 => return C.E4;
 105          when 5 => return C.E5;
 106          when 6 => return C.E6;
 107          when 7 => return C.E7;
 108       end case;
 109    end Get_12;
 110
 111    -------------
 112    -- GetU_12 --
 113    -------------
 114
 115    function GetU_12 (Arr : System.Address; N : Natural) return Bits_12 is
 116       C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
 117
 118    begin
 119       case N07 (Uns (N) mod 8) is
 120          when 0 => return C.E0;
 121          when 1 => return C.E1;
 122          when 2 => return C.E2;
 123          when 3 => return C.E3;
 124          when 4 => return C.E4;
 125          when 5 => return C.E5;
 126          when 6 => return C.E6;
 127          when 7 => return C.E7;
 128       end case;
 129    end GetU_12;
 130
 131    ------------
 132    -- Set_12 --
 133    ------------
 134
 135    procedure Set_12 (Arr : System.Address; N : Natural; E : Bits_12) is
 136       C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
 137
 138    begin
 139       case N07 (Uns (N) mod 8) is
 140          when 0 => C.E0 := E;
 141          when 1 => C.E1 := E;
 142          when 2 => C.E2 := E;
 143          when 3 => C.E3 := E;
 144          when 4 => C.E4 := E;
 145          when 5 => C.E5 := E;
 146          when 6 => C.E6 := E;
 147          when 7 => C.E7 := E;
 148       end case;
 149    end Set_12;
 150
 151    -------------
 152    -- SetU_12 --
 153    -------------
 154
 155    procedure SetU_12 (Arr : System.Address; N : Natural; E : Bits_12) is
 156       C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
 157
 158    begin
 159       case N07 (Uns (N) mod 8) is
 160          when 0 => C.E0 := E;
 161          when 1 => C.E1 := E;
 162          when 2 => C.E2 := E;
 163          when 3 => C.E3 := E;
 164          when 4 => C.E4 := E;
 165          when 5 => C.E5 := E;
 166          when 6 => C.E6 := E;
 167          when 7 => C.E7 := E;
 168       end case;
 169    end SetU_12;
 170
 171 end System.Pack_12;