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LibCrypto: Parse negative input correctly in BigFraction::from_string()

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Previously, when calling `BigFraction::from_string()`, the fractional
part of the number was always treated as positive. This led to an
incorrect result if the input string was negative.
This commit is contained in:
Tim Ledbetter 2024-01-14 06:14:56 +00:00 • committed by Jelle Raaijmakers
parent e0fd5beb36
commit d545fb2b60
Notes: sideshowbarker 2024-07-17 06:40:21 +09:00
3 changed files with 32 additions and 0 deletions
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1
Tests/LibCrypto/CMakeLists.txt
View file

@ -1,6 +1,7 @@
set(TEST_SOURCES
TestAES.cpp
TestASN1.cpp
TestBigFraction.cpp
TestBigInteger.cpp
TestChecksum.cpp
TestChaCha20.cpp

28
Tests/LibCrypto/TestBigFraction.cpp Normal file
View file

@ -0,0 +1,28 @@
/*
* Copyright (c) 2024, Tim Ledbetter <timledbetter@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibCrypto/BigFraction/BigFraction.h>
#include <LibTest/TestCase.h>
TEST_CASE(roundtrip_from_string)
{
Array valid_number_strings {
"0.1"sv,
"-0.1"sv,
"0.9"sv,
"-0.9"sv,
"1.2"sv,
"-1.2"sv,
"610888968122787804679.305596150292503043363"sv,
"-610888968122787804679.305596150292503043363"sv
};
for (auto valid_number_string : valid_number_strings) {
auto result = TRY_OR_FAIL(Crypto::BigFraction::from_string(valid_number_string));
auto precision = valid_number_string.length() - valid_number_string.find('.').value();
EXPECT_EQ(result.to_byte_string(precision), valid_number_string);
}
}

3
Userland/Libraries/LibCrypto/BigFraction/BigFraction.cpp
View file

@ -36,6 +36,9 @@ ErrorOr<BigFraction> BigFraction::from_string(StringView sv)
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)));
}