------------------------------------------------------------------------------ -- -- -- 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 -- -- . -- -- -- -- 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;