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LibCrypto: Add a rounding mode to UnsignedBigInteger::to_double

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This allows using different options for rounding, like IEEE
roundTiesToEven, which is the mode that JS requires.

Also fix that the last word read from the bigint for the mantissa could
be shifted incorrectly leading to incorrect results.
This commit is contained in:
davidot 2022-08-25 17:56:34 +02:00 • committed by Linus Groh
parent 8ba6e96d05
commit 77d71a5ffd
5 changed files with 144 additions and 24 deletions
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11
Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
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@ -1,6 +1,7 @@
/*
* Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
* Copyright (c) 2022, the SerenityOS developers.
* Copyright (c) 2022, David Tuin <davidot@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -58,7 +59,15 @@ public:
[[nodiscard]] String to_base(u16 N) const;
[[nodiscard]] u64 to_u64() const;
[[nodiscard]] double to_double() const;
enum class RoundingMode {
IEEERoundAndTiesToEvenMantissa,
RoundTowardZero,
// “the Number value for x”, https://tc39.es/ecma262/#number-value-for
ECMAScriptNumberValueFor = IEEERoundAndTiesToEvenMantissa,
};
[[nodiscard]] double to_double(RoundingMode rounding_mode = RoundingMode::IEEERoundAndTiesToEvenMantissa) const;
[[nodiscard]] Vector<Word, STARTING_WORD_SIZE> const& words() const { return m_words; }