| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT COMPILER COMPONENTS -- |
| -- -- |
| -- S Y S T E M . B I G N U M S -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 2012, 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 provides arbitrary precision signed integer arithmetic for |
| -- use in computing intermediate values in expressions for the case where |
| -- pragma Overflow_Check (Eliminated) is in effect. |
| |
| with Interfaces; |
| |
| package System.Bignums is |
| |
| pragma Assert (Long_Long_Integer'Size = 64); |
| -- This package assumes that Long_Long_Integer size is 64 bit (i.e. that it |
| -- has a range of -2**63 to 2**63-1). The front end ensures that the mode |
| -- ELIMINATED is not allowed for overflow checking if this is not the case. |
| |
| subtype Length is Natural range 0 .. 2 ** 23 - 1; |
| -- Represent number of words in Digit_Vector |
| |
| Base : constant := 2 ** 32; |
| -- Digit vectors use this base |
| |
| subtype SD is Interfaces.Unsigned_32; |
| -- Single length digit |
| |
| type Digit_Vector is array (Length range <>) of SD; |
| -- Represent digits of a number (most significant digit first) |
| |
| type Bignum_Data (Len : Length) is record |
| Neg : Boolean; |
| -- Set if value is negative, never set for zero |
| |
| D : Digit_Vector (1 .. Len); |
| -- Digits of number, most significant first, represented in base |
| -- 2**Base. No leading zeroes are stored, and the value of zero is |
| -- represented using an empty vector for D. |
| end record; |
| |
| for Bignum_Data use record |
| Len at 0 range 0 .. 23; |
| Neg at 3 range 0 .. 7; |
| end record; |
| |
| type Bignum is access all Bignum_Data; |
| -- This is the type that is used externally. Possibly this could be a |
| -- private type, but we leave the structure exposed for now. For one |
| -- thing it helps with debugging. Note that this package never shares |
| -- an allocated Bignum value, so for example for X + 0, a copy of X is |
| -- returned, not X itself. |
| |
| -- Note: none of the subprograms in this package modify the Bignum_Data |
| -- records referenced by Bignum arguments of mode IN. |
| |
| function Big_Add (X, Y : Bignum) return Bignum; -- "+" |
| function Big_Sub (X, Y : Bignum) return Bignum; -- "-" |
| function Big_Mul (X, Y : Bignum) return Bignum; -- "*" |
| function Big_Div (X, Y : Bignum) return Bignum; -- "/" |
| function Big_Exp (X, Y : Bignum) return Bignum; -- "**" |
| function Big_Mod (X, Y : Bignum) return Bignum; -- "mod" |
| function Big_Rem (X, Y : Bignum) return Bignum; -- "rem" |
| function Big_Neg (X : Bignum) return Bignum; -- "-" |
| function Big_Abs (X : Bignum) return Bignum; -- "abs" |
| -- Perform indicated arithmetic operation on bignum values. No exception |
| -- raised except for Div/Mod/Rem by 0 which raises Constraint_Error with |
| -- an appropriate message. |
| |
| function Big_EQ (X, Y : Bignum) return Boolean; -- "=" |
| function Big_NE (X, Y : Bignum) return Boolean; -- "/=" |
| function Big_GE (X, Y : Bignum) return Boolean; -- ">=" |
| function Big_LE (X, Y : Bignum) return Boolean; -- "<=" |
| function Big_GT (X, Y : Bignum) return Boolean; -- ">" |
| function Big_LT (X, Y : Bignum) return Boolean; -- "<" |
| -- Perform indicated comparison on bignums, returning result as Boolean. |
| -- No exception raised for any input arguments. |
| |
| function Bignum_In_LLI_Range (X : Bignum) return Boolean; |
| -- Returns True if the Bignum value is in the range of Long_Long_Integer, |
| -- so that a call to From_Bignum is guaranteed not to raise an exception. |
| |
| function To_Bignum (X : Long_Long_Integer) return Bignum; |
| -- Convert Long_Long_Integer to Bignum. No exception can be raised for any |
| -- input argument. |
| |
| function From_Bignum (X : Bignum) return Long_Long_Integer; |
| -- Convert Bignum to Long_Long_Integer. Constraint_Error raised with |
| -- appropriate message if value is out of range of Long_Long_Integer. |
| |
| end System.Bignums; |
