1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . P A C K _ 2 1 --
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, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, 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_21
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_21
;
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
);
80 function Get_21
(Arr
: System
.Address
; N
: Natural) return Bits_21
is
81 C
: constant Cluster_Ref
:= To_Ref
(Arr
+ Bits
* Ofs
(Uns
(N
) / 8));
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
;
100 procedure Set_21
(Arr
: System
.Address
; N
: Natural; E
: Bits_21
) is
101 C
: constant Cluster_Ref
:= To_Ref
(Arr
+ Bits
* Ofs
(Uns
(N
) / 8));
104 case N07
(Uns
(N
) mod 8) is