------------------------------------------------------------------------------
--                                                                          --
--                          GNAT RUN-TIME COMPONENTS                        --
--                                                                          --
--                  S Y S T E M . S C A L A R _ V A L U E S                 --
--                                                                          --
--                                 S p e c                                  --
--                                                                          --
--          Copyright (C) 2001-2020, 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 3,  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.                                     --
--                                                                          --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception,   --
-- version 3.1, as published by the Free Software Foundation.               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- <http://www.gnu.org/licenses/>.                                          --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc.      --
--                                                                          --
------------------------------------------------------------------------------

--  This package defines the constants used for initializing scalar values
--  when pragma Initialize_Scalars is used. The actual values are defined
--  in the binder generated file. This package contains the Ada names that
--  are used by the generated code, which are linked to the actual values
--  by the use of pragma Import.

with Interfaces;

package System.Scalar_Values is

   --  Note: logically this package should be Pure since it can be accessed
   --  from pure units, but the IS_xxx variables below get set at run time,
   --  so they have to be library level variables. In fact we only ever
   --  access this from generated code, and the compiler knows that it is
   --  OK to access this unit from generated code.

   subtype Byte1 is Interfaces.Unsigned_8;
   subtype Byte2 is Interfaces.Unsigned_16;
   subtype Byte4 is Interfaces.Unsigned_32;
   subtype Byte8 is Interfaces.Unsigned_64;

   --  The explicit initializations here are not really required, since these
   --  variables are always set by System.Scalar_Values.Initialize.

   IS_Is1 : Byte1 := 0;  -- Initialize 1 byte signed
   IS_Is2 : Byte2 := 0;  -- Initialize 2 byte signed
   IS_Is4 : Byte4 := 0;  -- Initialize 4 byte signed
   IS_Is8 : Byte8 := 0;  -- Initialize 8 byte signed
   --  For the above cases, the undefined value (set by the binder -Sin switch)
   --  is the largest negative number (1 followed by all zero bits).

   IS_Iu1 : Byte1 := 0;  -- Initialize 1 byte unsigned
   IS_Iu2 : Byte2 := 0;  -- Initialize 2 byte unsigned
   IS_Iu4 : Byte4 := 0;  -- Initialize 4 byte unsigned
   IS_Iu8 : Byte8 := 0;  -- Initialize 8 byte unsigned
   --  For the above cases, the undefined value (set by the binder -Sin switch)
   --  is the largest unsigned number (all 1 bits).

   IS_Iz1 : Byte1 := 0;  -- Initialize 1 byte zeroes
   IS_Iz2 : Byte2 := 0;  -- Initialize 2 byte zeroes
   IS_Iz4 : Byte4 := 0;  -- Initialize 4 byte zeroes
   IS_Iz8 : Byte8 := 0;  -- Initialize 8 byte zeroes
   --  For the above cases, the undefined value (set by the binder -Sin switch)
   --  is the zero (all 0 bits). This is used when zero is known to be an
   --  invalid value.

   --  The float definitions are aliased, because we use overlays to set them

   IS_Isf : aliased Short_Float     := 0.0;  -- Initialize short float
   IS_Ifl : aliased Float           := 0.0;  -- Initialize float
   IS_Ilf : aliased Long_Float      := 0.0;  -- Initialize long float
   IS_Ill : aliased Long_Long_Float := 0.0;  -- Initialize long long float

   procedure Initialize (Mode1 : Character; Mode2 : Character);
   --  This procedure is called from the binder when Initialize_Scalars mode
   --  is active. The arguments are the two characters from the -S switch,
   --  with letters forced upper case. So for example if -S5a is given, then
   --  Mode1 will be '5' and Mode2 will be 'A'. If the parameters are EV,
   --  then this routine reads the environment variable GNAT_INIT_SCALARS.
   --  The possible settings are the same as those for the -S switch (except
   --  for EV), i.e. IN/LO/HO/xx, xx = 2 hex digits. If no -S switch is given
   --  then the default of IN (invalid values) is passed on the call.

end System.Scalar_Values;
