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LibCrypto+LibJS: Move Power to method of {Unsigned,Signed}BigInteger

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Having it as a method instead of a free function is necessary for the
next commits and generally allows for optimizations that require deeper
access into the `UnsignedBigInteger` / `SignedBigInteger`.

Also restrict the exponent to 32 bits to avoid huge memory allocations.
This commit is contained in:
devgianlu 2025-04-26 11:17:32 +02:00 • committed by Jelle Raaijmakers
commit 5a4cfd05d0
Notes: github-actions[bot] 2025-05-23 09:58:36 +00:00
7 changed files with 53 additions and 46 deletions
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10
Libraries/LibCrypto/BigFraction/BigFraction.cpp
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@ -5,12 +5,11 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "BigFraction.h"
#include <AK/ByteString.h>
#include <AK/Math.h>
#include <AK/StringBuilder.h>
#include <LibCrypto/BigFraction/BigFraction.h>
#include <LibCrypto/BigInt/UnsignedBigInteger.h>
#include <LibCrypto/NumberTheory/ModularFunctions.h>
namespace Crypto {
@ -36,12 +35,11 @@ ErrorOr<BigFraction> BigFraction::from_string(StringView sv)
auto integer_part = TRY(SignedBigInteger::from_base(10, integer_part_view));
auto fractional_part = TRY(SignedBigInteger::from_base(10, fraction_part_view));
auto fraction_length = UnsignedBigInteger(static_cast<u64>(fraction_part_view.length()));
if (!sv.is_empty() && sv[0] == '-')
fractional_part.negate();
return BigFraction(move(integer_part)) + BigFraction(move(fractional_part), NumberTheory::Power("10"_bigint, move(fraction_length)));
return BigFraction(move(integer_part)) + BigFraction(move(fractional_part), "10"_bigint.pow(fraction_part_view.length()));
}
BigFraction BigFraction::operator+(BigFraction const& rhs) const
@ -129,7 +127,7 @@ BigFraction::BigFraction(double d)
d -= digit * AK::pow(10.0, (double)current_pow);
if (current_pow < 0) {
++decimal_places;
m_denominator.set_to(NumberTheory::Power("10"_bigint, UnsignedBigInteger { decimal_places }));
m_denominator.set_to("10"_bigint.pow(decimal_places));
}
current_pow -= 1;
}
@ -205,7 +203,7 @@ BigFraction BigFraction::rounded(unsigned rounding_threshold) const
auto res = m_numerator.divided_by(m_denominator);
BigFraction result { move(res.quotient) };
auto const needed_power = NumberTheory::Power("10"_bigint, UnsignedBigInteger { rounding_threshold });
auto const needed_power = "10"_bigint.pow(rounding_threshold);
// We get one more digit to do proper rounding
auto const fractional_value = res.remainder.multiplied_by(needed_power.multiplied_by("10"_bigint)).divided_by(m_denominator).quotient;