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5f1a30197c
This concept is rarely used in codebase and very much error-prone if you forget to check it. Instead, make it so that operations that would produce invalid integers return an error instead.
94 lines
2.7 KiB
C++
94 lines
2.7 KiB
C++
/*
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* Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
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* Copyright (c) 2020-2021, Dex♪ <dexes.ttp@gmail.com>
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* Copyright (c) 2024, Altomani Gianluca <altomanigianluca@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "UnsignedBigIntegerAlgorithms.h"
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namespace Crypto {
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void UnsignedBigIntegerAlgorithms::destructive_GCD_without_allocation(
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UnsignedBigInteger& temp_a,
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UnsignedBigInteger& temp_b,
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UnsignedBigInteger& temp_quotient,
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UnsignedBigInteger& temp_remainder,
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UnsignedBigInteger& output)
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{
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for (;;) {
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if (temp_a == 0) {
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output.set_to(temp_b);
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return;
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}
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// temp_b %= temp_a
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divide_without_allocation(temp_b, temp_a, temp_quotient, temp_remainder);
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temp_b.set_to(temp_remainder);
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if (temp_b == 0) {
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output.set_to(temp_a);
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return;
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}
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// temp_a %= temp_b
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divide_without_allocation(temp_a, temp_b, temp_quotient, temp_remainder);
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temp_a.set_to(temp_remainder);
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}
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}
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void UnsignedBigIntegerAlgorithms::extended_GCD_without_allocation(
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UnsignedBigInteger const& a,
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UnsignedBigInteger const& b,
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UnsignedBigInteger& x,
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UnsignedBigInteger& y,
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UnsignedBigInteger& gcd,
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UnsignedBigInteger& temp_quotient,
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UnsignedBigInteger& temp_1,
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UnsignedBigInteger& temp_2,
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UnsignedBigInteger& temp_shift,
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UnsignedBigInteger& temp_r,
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UnsignedBigInteger& temp_s,
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UnsignedBigInteger& temp_t)
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{
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gcd.set_to(a);
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x.set_to(1);
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y.set_to(0);
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temp_r.set_to(b);
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temp_s.set_to_0();
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temp_t.set_to(1);
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while (temp_r != 0) {
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// quotient := old_r div r
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divide_without_allocation(gcd, temp_r, temp_quotient, temp_1);
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temp_2.set_to(temp_r);
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multiply_without_allocation(temp_quotient, temp_r, temp_shift, temp_1);
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while (gcd < temp_1) {
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add_into_accumulator_without_allocation(gcd, b);
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}
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MUST(subtract_without_allocation(gcd, temp_1, temp_r));
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gcd.set_to(temp_2);
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// (old_s, s) := (s, old_s − quotient × s)
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temp_2.set_to(temp_s);
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multiply_without_allocation(temp_quotient, temp_s, temp_shift, temp_1);
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while (x < temp_1) {
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add_into_accumulator_without_allocation(x, b);
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}
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MUST(subtract_without_allocation(x, temp_1, temp_s));
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x.set_to(temp_2);
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// (old_t, t) := (t, old_t − quotient × t)
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temp_2.set_to(temp_t);
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multiply_without_allocation(temp_quotient, temp_t, temp_shift, temp_1);
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while (y < temp_1) {
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add_into_accumulator_without_allocation(y, b);
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}
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MUST(subtract_without_allocation(y, temp_1, temp_t));
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y.set_to(temp_2);
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}
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}
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}
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