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// Copyright 2017 Elias Kosunen
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// This file is a part of scnlib:
// https://github.com/eliaskosunen/scnlib
#ifndef SCN_UTIL_MATH_H
#define SCN_UTIL_MATH_H
#include "../detail/fwd.h"
#include <cmath>
#include <limits>
namespace scn {
SCN_BEGIN_NAMESPACE
namespace detail {
template <typename Integral>
SCN_CONSTEXPR14 int _max_digits(int base) noexcept
{
using lim = std::numeric_limits<Integral>;
char base8_digits[8] = {3, 5, 0, 11, 0, 0, 0, 21};
if (base == 10) {
return lim::digits10;
}
if (base == 8) {
return static_cast<int>(base8_digits[sizeof(Integral) - 1]);
}
if (base == lim::radix) {
return lim::digits;
}
auto i = lim::max();
Integral digits = 0;
while (i) {
i /= static_cast<Integral>(base);
digits++;
}
return static_cast<int>(digits);
}
/**
* Returns the maximum number of digits that an integer in base `base`
* can have, including the sign.
*
* If `base == 0`, uses `2` (longest), and adds 2 to the result, to
* accommodate for a base prefix (e.g. `0x`)
*/
template <typename Integral>
SCN_CONSTEXPR14 int max_digits(int base) noexcept
{
auto b = base == 0 ? 2 : base;
auto d = _max_digits<Integral>(b) +
(std::is_signed<Integral>::value ? 1 : 0);
if (base == 0) {
return d + 2; // accommodate for 0x/0o
}
return d;
}
/**
* Implementation of `std::div`, which is constexpr pre-C++23
*/
template <typename T>
constexpr std::pair<T, T> div(T l, T r) noexcept
{
return {l / r, l % r};
}
template <typename T>
struct zero_value;
template <>
struct zero_value<float> {
static constexpr float value = 0.0f;
};
template <>
struct zero_value<double> {
static constexpr double value = 0.0;
};
template <>
struct zero_value<long double> {
static constexpr long double value = 0.0l;
};
/**
* Returns `true` if `ch` is a digit for an integer in base `base`.
*/
template <typename CharT>
bool is_base_digit(CharT ch, int base)
{
if (base <= 10) {
return ch >= static_cast<CharT>('0') &&
ch <= static_cast<CharT>('0') + base - 1;
}
return is_base_digit(ch, 10) ||
(ch >= static_cast<CharT>('a') &&
ch <= static_cast<CharT>('a') + base - 1) ||
(ch >= static_cast<CharT>('A') &&
ch <= static_cast<CharT>('A') + base - 1);
}
} // namespace detail
SCN_END_NAMESPACE
} // namespace scn
#endif
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