compiletimedigits.h
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/* ****************************************************************************
* Copyright 2019 Open Systems Development BV *
* *
* Permission is hereby granted, free of charge, to any person obtaining a *
* copy of this software and associated documentation files (the "Software"), *
* to deal in the Software without restriction, including without limitation *
* the rights to use, copy, modify, merge, publish, distribute, sublicense, *
* and/or sell copies of the Software, and to permit persons to whom the *
* Software is furnished to do so, subject to the following conditions: *
* *
* The above copyright notice and this permission notice shall be included in *
* all copies or substantial portions of the Software. *
* *
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, *
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL *
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER *
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING *
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER *
* DEALINGS IN THE SOFTWARE. *
* ***************************************************************************/
#ifndef OSDEV_COMPONENTS_MQTT_COMPILETIMEDIGITS_H
#define OSDEV_COMPONENTS_MQTT_COMPILETIMEDIGITS_H
// std
#include <string>
#include "compiletimestring.h"
namespace osdev {
namespace components {
namespace mqtt {
/**
* @brief Calculate the number of digits needed to represent a given value in a given base.
* @tparam B The base to use.
* @param value The value to represent.
* @return The number of digits.
*/
template <unsigned B>
constexpr std::size_t numberOfDigits(unsigned value) noexcept
{
static_assert(B > 0, "base must be larger than zero");
return (value / B) == 0 ? 1 : (1 + numberOfDigits<B>(value / B));
}
/**
* @return stringified digit that represents the given single digit value.
* @note Values can range from 0 to 37 inclusive which maps on 0-9A-Z.
*/
template <unsigned value>
constexpr char digit() noexcept
{
static_assert(value <= 37, "Value must lie between 0 and 37 both inclusive");
return (value < 10 ? '0' + static_cast<char>(value) : 'A' + static_cast<char>(value) - 10);
}
/**
* @brief Recursive template definition that is used to determine the value of a given number N in a given base B.
* @tparam N The number to obtain the representation for.
* @tparam B The base to use.
* @tparam Len The length of the representation including the 0 terminator.
* If not provided the length is calculated on first instantiation of this template.
* @tparam remains Empty parameter pack on first instantiation. Will be filled further by every following instantiation.
*/
template <unsigned N, unsigned B, std::size_t Len = numberOfDigits<B>(N) + 1, unsigned... remains>
struct Digits
{
static constexpr auto create() noexcept -> std::array<char, Len>
{
static_assert(B > 0, "base must be larger than zero");
return Digits<N / B, B, Len, digit<N % B>(), remains...>::create();
}
};
/**
* @brief Termination template that will return the actual hex digit array that represents the given value.
* @tparam B The base to use.
* @tparam Len The length of the hexadecimal representation including 0 terminator.
* @tparam remains Parameter pack that contains the hexadecimal character representations.
*/
template <unsigned B, std::size_t Len, unsigned... remains>
struct Digits<0, B, Len, remains...>
{
static constexpr auto create() noexcept -> std::array<char, Len>
{
static_assert(sizeof...(remains) + 1 == Len, "Parameter 'Len' must be equal to the length of the parameter pack 'remains' including the termination zero");
return std::array<char, Len>{ { remains..., 0 } };
}
};
/**
* @brief Digits builder can be used in combination with the compiletime_string.
* @tparam N The number to obtain the compile time string representation for.
* @tparam B The base to use (up to 37).
* This template struct defines a produce() method and the return type of that method.
*/
template <unsigned N, unsigned B>
struct ProduceDigits
{
/**
* @brief Return type definition of the produce method.
*/
using return_t = std::array<char, numberOfDigits<B>(N) + 1>;
/**
* @brief Produce the actual representation.
*/
static constexpr return_t produce() noexcept
{
return Digits<N, B>::create();
}
};
} // End namespace mqtt
} // End namespace components
} // End namespace osdev
#endif // OSDEV_COMPONENTS_MQTT_COMPILETIMEDIGITS_H