1 ------------------------------------------------------------------------------
3 -- GNAT RUNTIME COMPONENTS --
5 -- S Y S T E M . P A C K _ 1 8 --
11 -- Copyright (C) 1992-1999 Free Software Foundation, Inc. --
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. --
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. --
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). --
34 ------------------------------------------------------------------------------
36 with System
.Storage_Elements
;
37 with System
.Unsigned_Types
;
38 with Unchecked_Conversion
;
40 package body System
.Pack_18
is
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;
46 use type System
.Storage_Elements
.Storage_Offset
;
47 use type System
.Unsigned_Types
.Unsigned
;
49 type Cluster
is record
50 E0
, E1
, E2
, E3
, E4
, E5
, E6
, E7
: Bits_18
;
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;
64 for Cluster
'Size use Bits
* 8;
66 for Cluster
'Alignment use Integer'Min (Standard
'Maximum_Alignment,
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.
73 type Cluster_Ref
is access Cluster
;
75 function To_Ref
is new
76 Unchecked_Conversion
(System
.Address
, Cluster_Ref
);
78 -- The following declarations are for the case where the address
79 -- passed to GetU_18 or SetU_18 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.
83 type ClusterU
is new Cluster
;
84 for ClusterU
'Alignment use 1;
86 type ClusterU_Ref
is access ClusterU
;
88 function To_Ref
is new
89 Unchecked_Conversion
(System
.Address
, ClusterU_Ref
);
95 function Get_18
(Arr
: System
.Address
; N
: Natural) return Bits_18
is
96 C
: constant Cluster_Ref
:= To_Ref
(Arr
+ Bits
* Ofs
(Uns
(N
) / 8));
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
;
115 function GetU_18
(Arr
: System
.Address
; N
: Natural) return Bits_18
is
116 C
: constant ClusterU_Ref
:= To_Ref
(Arr
+ Bits
* Ofs
(Uns
(N
) / 8));
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
;
135 procedure Set_18
(Arr
: System
.Address
; N
: Natural; E
: Bits_18
) is
136 C
: constant Cluster_Ref
:= To_Ref
(Arr
+ Bits
* Ofs
(Uns
(N
) / 8));
139 case N07
(Uns
(N
) mod 8) is
155 procedure SetU_18
(Arr
: System
.Address
; N
: Natural; E
: Bits_18
) is
156 C
: constant ClusterU_Ref
:= To_Ref
(Arr
+ Bits
* Ofs
(Uns
(N
) / 8));
159 case N07
(Uns
(N
) mod 8) is