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AK: Add framework for a unified floating point to string conversion

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Currently, the floating point to string conversion is implemented
several times across the codebase. This commit provides a pretty
low-level function to unify all of such conversions. It converts the
given double to a fixed point decimal satisfying a few correctness
criteria.
This commit is contained in:
Dan Klishch 2022-10-25 14:00:49 -04:00 • committed by Andrew Kaster
parent 17c9a3e8d9
commit fdc53a5995
5 changed files with 1243 additions and 0 deletions
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43
AK/StringFloatingPointConversions.h Normal file
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/*
* Copyright (c) 2022, Dan Klishch <danilklishch@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#ifdef KERNEL
# error This file should not be included in the KERNEL, as doubles should not appear in the \
kernel code, although the conversion currently does not use any floating point \
computations.
#endif
#include <AK/Concepts.h>
#include <AK/Types.h>
namespace AK {
struct FloatingPointExponentialForm {
bool sign;
u64 fraction;
i32 exponent;
};
/// This function finds the representation of `value' in the form of
/// `(-1) ^ sign * fraction * 10 ^ exponent', such that (applying in the order of enumeration):
///
/// 1. sign is either 0 or 1, fraction is a non-negative number, exponent is an integer.
/// 2. For +0, it is {.sign = 0, .fraction = 0, .exponent = 0},
/// for -0, is {.sign = 1, .fraction = 0, .exponent = 0},
/// for +inf, -inf, and NaN is undefined.
/// 3. `(-1) ^ sign * fraction * 10 ^ exponent', computed with an infinite precision, rounds to
/// `value' in the half to even mode.
/// 4. len(str(fraction)) is minimal.
/// 5. `abs((-1) ^ sign * fraction * 10 ^ exponent - value)' is minimal.
/// 6. fraction is even.
template<FloatingPoint T>
FloatingPointExponentialForm convert_floating_point_to_decimal_exponential_form(T value);
}
using AK::convert_floating_point_to_decimal_exponential_form;