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+------------------------------------------------------------------------------
+-- --
+-- GNAT RUN-TIME COMPONENTS --
+-- --
+-- S Y S T E M . P A C K _ 2 4 --
+-- --
+-- B o d y --
+-- --
+-- Copyright (C) 1992-2005, Free Software Foundation, Inc. --
+-- --
+-- GNAT is free software; you can redistribute it and/or modify it under --
+-- terms of the GNU General Public License as published by the Free Soft- --
+-- ware Foundation; either version 2, or (at your option) any later ver- --
+-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
+-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
+-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
+-- for more details. You should have received a copy of the GNU General --
+-- Public License distributed with GNAT; see file COPYING. If not, write --
+-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
+-- Boston, MA 02110-1301, USA. --
+-- --
+-- As a special exception, if other files instantiate generics from this --
+-- unit, or you link this unit with other files to produce an executable, --
+-- this unit does not by itself cause the resulting executable to be --
+-- covered by the GNU General Public License. This exception does not --
+-- however invalidate any other reasons why the executable file might be --
+-- covered by the GNU Public License. --
+-- --
+-- GNAT was originally developed by the GNAT team at New York University. --
+-- Extensive contributions were provided by Ada Core Technologies Inc. --
+-- --
+------------------------------------------------------------------------------
+
+with System.Storage_Elements;
+with System.Unsigned_Types;
+with Unchecked_Conversion;
+
+package body System.Pack_24 is
+
+ subtype Ofs is System.Storage_Elements.Storage_Offset;
+ subtype Uns is System.Unsigned_Types.Unsigned;
+ subtype N07 is System.Unsigned_Types.Unsigned range 0 .. 7;
+
+ use type System.Storage_Elements.Storage_Offset;
+ use type System.Unsigned_Types.Unsigned;
+
+ type Cluster is record
+ E0, E1, E2, E3, E4, E5, E6, E7 : Bits_24;
+ end record;
+
+ for Cluster use record
+ E0 at 0 range 0 * Bits .. 0 * Bits + Bits - 1;
+ E1 at 0 range 1 * Bits .. 1 * Bits + Bits - 1;
+ E2 at 0 range 2 * Bits .. 2 * Bits + Bits - 1;
+ E3 at 0 range 3 * Bits .. 3 * Bits + Bits - 1;
+ E4 at 0 range 4 * Bits .. 4 * Bits + Bits - 1;
+ E5 at 0 range 5 * Bits .. 5 * Bits + Bits - 1;
+ E6 at 0 range 6 * Bits .. 6 * Bits + Bits - 1;
+ E7 at 0 range 7 * Bits .. 7 * Bits + Bits - 1;
+ end record;
+
+ for Cluster'Size use Bits * 8;
+
+ for Cluster'Alignment use Integer'Min (Standard'Maximum_Alignment,
+ 1 +
+ 1 * Boolean'Pos (Bits mod 2 = 0) +
+ 2 * Boolean'Pos (Bits mod 4 = 0));
+ -- Use maximum possible alignment, given the bit field size, since this
+ -- will result in the most efficient code possible for the field.
+
+ type Cluster_Ref is access Cluster;
+
+ function To_Ref is new
+ Unchecked_Conversion (System.Address, Cluster_Ref);
+
+ -- The following declarations are for the case where the address
+ -- passed to GetU_24 or SetU_24 is not guaranteed to be aligned.
+ -- These routines are used when the packed array is itself a
+ -- component of a packed record, and therefore may not be aligned.
+
+ type ClusterU is new Cluster;
+ for ClusterU'Alignment use 1;
+
+ type ClusterU_Ref is access ClusterU;
+
+ function To_Ref is new
+ Unchecked_Conversion (System.Address, ClusterU_Ref);
+
+ ------------
+ -- Get_24 --
+ ------------
+
+ function Get_24 (Arr : System.Address; N : Natural) return Bits_24 is
+ C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
+ begin
+ case N07 (Uns (N) mod 8) is
+ when 0 => return C.E0;
+ when 1 => return C.E1;
+ when 2 => return C.E2;
+ when 3 => return C.E3;
+ when 4 => return C.E4;
+ when 5 => return C.E5;
+ when 6 => return C.E6;
+ when 7 => return C.E7;
+ end case;
+ end Get_24;
+
+ -------------
+ -- GetU_24 --
+ -------------
+
+ function GetU_24 (Arr : System.Address; N : Natural) return Bits_24 is
+ C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
+ begin
+ case N07 (Uns (N) mod 8) is
+ when 0 => return C.E0;
+ when 1 => return C.E1;
+ when 2 => return C.E2;
+ when 3 => return C.E3;
+ when 4 => return C.E4;
+ when 5 => return C.E5;
+ when 6 => return C.E6;
+ when 7 => return C.E7;
+ end case;
+ end GetU_24;
+
+ ------------
+ -- Set_24 --
+ ------------
+
+ procedure Set_24 (Arr : System.Address; N : Natural; E : Bits_24) is
+ C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
+ begin
+ case N07 (Uns (N) mod 8) is
+ when 0 => C.E0 := E;
+ when 1 => C.E1 := E;
+ when 2 => C.E2 := E;
+ when 3 => C.E3 := E;
+ when 4 => C.E4 := E;
+ when 5 => C.E5 := E;
+ when 6 => C.E6 := E;
+ when 7 => C.E7 := E;
+ end case;
+ end Set_24;
+
+ -------------
+ -- SetU_24 --
+ -------------
+
+ procedure SetU_24 (Arr : System.Address; N : Natural; E : Bits_24) is
+ C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));
+ begin
+ case N07 (Uns (N) mod 8) is
+ when 0 => C.E0 := E;
+ when 1 => C.E1 := E;
+ when 2 => C.E2 := E;
+ when 3 => C.E3 := E;
+ when 4 => C.E4 := E;
+ when 5 => C.E5 := E;
+ when 6 => C.E6 := E;
+ when 7 => C.E7 := E;
+ end case;
+ end SetU_24;
+
+end System.Pack_24;