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------------------------------------------------------------------------------

--                                                                          --

--                          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) 2001-2009, 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.

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.

   type Byte1 is mod 2 **  8;

   type Byte2 is mod 2 ** 16;

   type Byte4 is mod 2 ** 32;

   type Byte8 is mod 2 ** 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;