1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . P A C K _ 2 8 --
9 -- Copyright (C) 1992-2005 Free Software Foundation, Inc. --
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. --
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. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 with System.Storage_Elements;
35 with System.Unsigned_Types;
36 with Unchecked_Conversion;
38 package body System.Pack_28 is
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;
44 use type System.Storage_Elements.Storage_Offset;
45 use type System.Unsigned_Types.Unsigned;
47 type Cluster is record
48 E0, E1, E2, E3, E4, E5, E6, E7 : Bits_28;
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;
62 for Cluster'Size use Bits * 8;
64 for Cluster'Alignment use Integer'Min (Standard'Maximum_Alignment,
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.
71 type Cluster_Ref is access Cluster;
73 function To_Ref is new
74 Unchecked_Conversion (System.Address, Cluster_Ref);
76 -- The following declarations are for the case where the address
77 -- passed to GetU_28 or SetU_28 is not guaranteed to be aligned.
78 -- These routines are used when the packed array is itself a
79 -- component of a packed record, and therefore may not be aligned.
81 type ClusterU is new Cluster;
82 for ClusterU'Alignment use 1;
84 type ClusterU_Ref is access ClusterU;
86 function To_Ref is new
87 Unchecked_Conversion (System.Address, ClusterU_Ref);
93 function Get_28 (Arr : System.Address; N : Natural) return Bits_28 is
94 C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
97 case N07 (Uns (N) mod 8) is
98 when 0 => return C.E0;
99 when 1 => return C.E1;
100 when 2 => return C.E2;
101 when 3 => return C.E3;
102 when 4 => return C.E4;
103 when 5 => return C.E5;
104 when 6 => return C.E6;
105 when 7 => return C.E7;
113 function GetU_28 (Arr : System.Address; N : Natural) return Bits_28 is
114 C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
117 case N07 (Uns (N) mod 8) is
118 when 0 => return C.E0;
119 when 1 => return C.E1;
120 when 2 => return C.E2;
121 when 3 => return C.E3;
122 when 4 => return C.E4;
123 when 5 => return C.E5;
124 when 6 => return C.E6;
125 when 7 => return C.E7;
133 procedure Set_28 (Arr : System.Address; N : Natural; E : Bits_28) is
134 C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
137 case N07 (Uns (N) mod 8) is
153 procedure SetU_28 (Arr : System.Address; N : Natural; E : Bits_28) is
154 C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
157 case N07 (Uns (N) mod 8) is