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------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                      S Y S T E M . A R I T H _ 6 4                       --
--                                                                          --
--                                 S p e c                                  --
--                                                                          --
--        Copyright (C) 1994,1995,1996 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,  59 Temple Place - Suite 330,  Boston, --
-- MA 02111-1307, 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.      --
--                                                                          --
------------------------------------------------------------------------------

--  This unit provides software routines for doing arithmetic on 64-bit
--  signed integer values in cases where either overflow checking is
--  required, or intermediate results are longer than 64 bits.

with Interfaces;

package System.Arith_64 is
pragma Pure (Arith_64);

   subtype Int64 is Interfaces.Integer_64;

   function Add_With_Ovflo_Check (X, Y : Int64) return Int64;
   --  Raises Constraint_Error if sum of operands overflows 64 bits,
   --  otherwise returns the 64-bit signed integer sum.

   function Subtract_With_Ovflo_Check (X, Y : Int64) return Int64;
   --  Raises Constraint_Error if difference of operands overflows 64
   --  bits, otherwise returns the 64-bit signed integer difference.

   function Multiply_With_Ovflo_Check (X, Y : Int64) return Int64;
   --  Raises Constraint_Error if product of operands overflows 64
   --  bits, otherwise returns the 64-bit signed integer difference.

   procedure Scaled_Divide
     (X, Y, Z : Int64;
      Q, R    : out Int64;
      Round   : Boolean);
   --  Performs the division of (X * Y) / Z, storing the quotient in Q
   --  and the remainder in R. Constraint_Error is raised if Z is zero,
   --  or if the quotient does not fit in 64-bits. Round indicates if
   --  the result should be rounded. If Round is False, then Q, R are
   --  the normal quotient and remainder from a truncating division.
   --  If Round is True, then Q is the rounded quotient. the remainder
   --  R is not affected by the setting of the Round flag.

   procedure Double_Divide
     (X, Y, Z : Int64;
      Q, R    : out Int64;
      Round   : Boolean);
   --  Performs the division X / (Y * Z), storing the quotient in Q and
   --  the remainder in R. Constraint_Error is raised if Y or Z is zero.
   --  Round indicates if the result should be rounded. If Round is False,
   --  then Q, R are the normal quotient and remainder from a truncating
   --  division. If Round is True, then Q is the rounded quotient. The
   --  remainder R is not affected by the setting of the Round flag. The
   --  result is known to be in range except for the noted possibility of
   --  Y or Z being zero, so no other overflow checks are required.

end System.Arith_64;