1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUNTIME COMPONENTS                          --
4--                                                                          --
5--                       S Y S T E M . P A C K _ 3 1                        --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--          Copyright (C) 1992-1999 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,  59 Temple Place - Suite 330,  Boston, --
20-- MA 02111-1307, 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
34with System.Storage_Elements;
35with System.Unsigned_Types;
36with Unchecked_Conversion;
37
38package body System.Pack_31 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_31;
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_31 --
78   ------------
79
80   function Get_31 (Arr : System.Address; N : Natural) return Bits_31 is
81      C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
82
83   begin
84      case N07 (Uns (N) mod 8) is
85         when 0 => return C.E0;
86         when 1 => return C.E1;
87         when 2 => return C.E2;
88         when 3 => return C.E3;
89         when 4 => return C.E4;
90         when 5 => return C.E5;
91         when 6 => return C.E6;
92         when 7 => return C.E7;
93      end case;
94   end Get_31;
95
96   ------------
97   -- Set_31 --
98   ------------
99
100   procedure Set_31 (Arr : System.Address; N : Natural; E : Bits_31) is
101      C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
102
103   begin
104      case N07 (Uns (N) mod 8) is
105         when 0 => C.E0 := E;
106         when 1 => C.E1 := E;
107         when 2 => C.E2 := E;
108         when 3 => C.E3 := E;
109         when 4 => C.E4 := E;
110         when 5 => C.E5 := E;
111         when 6 => C.E6 := E;
112         when 7 => C.E7 := E;
113      end case;
114   end Set_31;
115
116end System.Pack_31;
117