gcc/ada/s-arit64.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                      S Y S T E M . A R I T H _ 6 4                       --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --                                                                          --
  10 --        Copyright (C) 1994,1995,1996 Free Software Foundation, Inc.       --
  11 --                                                                          --
  12 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  20 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNAT was originally developed  by the GNAT team at  New York University. --
  31 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  32 --                                                                          --
  33 ------------------------------------------------------------------------------
  34
  35 --  This unit provides software routines for doing arithmetic on 64-bit
  36 --  signed integer values in cases where either overflow checking is
  37 --  required, or intermediate results are longer than 64 bits.
  38
  39 with Interfaces;
  40
  41 package System.Arith_64 is
  42 pragma Pure (Arith_64);
  43
  44    subtype Int64 is Interfaces.Integer_64;
  45
  46    function Add_With_Ovflo_Check (X, Y : Int64) return Int64;
  47    --  Raises Constraint_Error if sum of operands overflows 64 bits,
  48    --  otherwise returns the 64-bit signed integer sum.
  49
  50    function Subtract_With_Ovflo_Check (X, Y : Int64) return Int64;
  51    --  Raises Constraint_Error if difference of operands overflows 64
  52    --  bits, otherwise returns the 64-bit signed integer difference.
  53
  54    function Multiply_With_Ovflo_Check (X, Y : Int64) return Int64;
  55    --  Raises Constraint_Error if product of operands overflows 64
  56    --  bits, otherwise returns the 64-bit signed integer difference.
  57
  58    procedure Scaled_Divide
  59      (X, Y, Z : Int64;
  60       Q, R    : out Int64;
  61       Round   : Boolean);
  62    --  Performs the division of (X * Y) / Z, storing the quotient in Q
  63    --  and the remainder in R. Constraint_Error is raised if Z is zero,
  64    --  or if the quotient does not fit in 64-bits. Round indicates if
  65    --  the result should be rounded. If Round is False, then Q, R are
  66    --  the normal quotient and remainder from a truncating division.
  67    --  If Round is True, then Q is the rounded quotient. the remainder
  68    --  R is not affected by the setting of the Round flag.
  69
  70    procedure Double_Divide
  71      (X, Y, Z : Int64;
  72       Q, R    : out Int64;
  73       Round   : Boolean);
  74    --  Performs the division X / (Y * Z), storing the quotient in Q and
  75    --  the remainder in R. Constraint_Error is raised if Y or Z is zero.
  76    --  Round indicates if the result should be rounded. If Round is False,
  77    --  then Q, R are the normal quotient and remainder from a truncating
  78    --  division. If Round is True, then Q is the rounded quotient. The
  79    --  remainder R is not affected by the setting of the Round flag. The
  80    --  result is known to be in range except for the noted possibility of
  81    --  Y or Z being zero, so no other overflow checks are required.
  82
  83 end System.Arith_64;