81 lines
3.9 KiB
Ada
81 lines
3.9 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- S Y S T E M . S H A R E D _ B I G N U M S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 2012-2020, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package provides declarations shared across all instantiations of
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-- System.Generic_Bignums.
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with Ada.Unchecked_Conversion;
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with Interfaces;
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package System.Shared_Bignums is
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pragma Preelaborate;
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pragma Assert (Long_Long_Integer'Size = 64);
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-- This package assumes that Long_Long_Integer size is 64 bit (i.e. that it
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-- has a range of -2**63 to 2**63-1). The front end ensures that the mode
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-- ELIMINATED is not allowed for overflow checking if this is not the case.
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subtype Length is Natural range 0 .. 2 ** 23 - 1;
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-- Represent number of words in Digit_Vector
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Base : constant := 2 ** 32;
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-- Digit vectors use this base
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subtype SD is Interfaces.Unsigned_32;
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-- Single length digit
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type Digit_Vector is array (Length range <>) of SD;
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-- Represent digits of a number (most significant digit first)
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type Bignum_Data (Len : Length) is record
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Neg : Boolean;
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-- Set if value is negative, never set for zero
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D : Digit_Vector (1 .. Len);
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-- Digits of number, most significant first, represented in base
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-- 2**Base. No leading zeroes are stored, and the value of zero is
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-- represented using an empty vector for D.
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end record;
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for Bignum_Data use record
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Len at 0 range 0 .. 23;
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Neg at 3 range 0 .. 7;
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end record;
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type Bignum is access all Bignum_Data;
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function To_Bignum is new Ada.Unchecked_Conversion (System.Address, Bignum);
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function To_Address is new
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Ada.Unchecked_Conversion (Bignum, System.Address);
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end System.Shared_Bignums;
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