1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                  S Y S T E M . A R I T H _ D O U B L E                   --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1992-2020, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This package provides software routines for doing arithmetic on "double"
33--  signed integer values in cases where either overflow checking is required,
34--  or intermediate results are longer than the result type.
35
36generic
37
38   type Double_Int is range <>;
39
40   type Double_Uns is mod <>;
41
42   type Single_Uns is mod <>;
43
44   with function Shift_Left (A : Double_Uns; B : Natural) return Double_Uns
45     is <>;
46
47   with function Shift_Right (A : Double_Uns; B : Natural) return Double_Uns
48     is <>;
49
50   with function Shift_Left (A : Single_Uns; B : Natural) return Single_Uns
51     is <>;
52
53package System.Arith_Double is
54   pragma Pure;
55
56   function Add_With_Ovflo_Check (X, Y : Double_Int) return Double_Int;
57   --  Raises Constraint_Error if sum of operands overflows Double_Int,
58   --  otherwise returns the signed integer sum.
59
60   function Subtract_With_Ovflo_Check (X, Y : Double_Int) return Double_Int;
61   --  Raises Constraint_Error if difference of operands overflows Double_Int,
62   --  otherwise returns the signed integer difference.
63
64   function Multiply_With_Ovflo_Check (X, Y : Double_Int) return Double_Int;
65   pragma Convention (C, Multiply_With_Ovflo_Check);
66   --  Raises Constraint_Error if product of operands overflows Double_Int,
67   --  otherwise returns the signed integer product. Gigi may also call this
68   --  routine directly.
69
70   procedure Scaled_Divide
71     (X, Y, Z : Double_Int;
72      Q, R    : out Double_Int;
73      Round   : Boolean);
74   --  Performs the division of (X * Y) / Z, storing the quotient in Q
75   --  and the remainder in R. Constraint_Error is raised if Z is zero,
76   --  or if the quotient does not fit in Double_Int. Round indicates if
77   --  the result should be rounded. If Round is False, then Q, R are
78   --  the normal quotient and remainder from a truncating division.
79   --  If Round is True, then Q is the rounded quotient. The remainder
80   --  R is not affected by the setting of the Round flag.
81
82   procedure Double_Divide
83     (X, Y, Z : Double_Int;
84      Q, R    : out Double_Int;
85      Round   : Boolean);
86   --  Performs the division X / (Y * Z), storing the quotient in Q and
87   --  the remainder in R. Constraint_Error is raised if Y or Z is zero,
88   --  or if the quotient does not fit in Double_Int. Round indicates if the
89   --  result should be rounded. If Round is False, then Q, R are the normal
90   --  quotient and remainder from a truncating division. If Round is True,
91   --  then Q is the rounded quotient. The remainder R is not affected by the
92   --  setting of the Round flag.
93
94end System.Arith_Double;
95