134 lines
3.6 KiB
C++
134 lines
3.6 KiB
C++
/*
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* Copyright (c) 2017, Matias Fontanini
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#ifndef TINS_SMALL_UINT_H
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#define TINS_SMALL_UINT_H
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#include <stdint.h>
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#include <stdexcept>
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namespace Tins {
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class value_too_large : public std::exception {
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public:
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const char* what() const throw() {
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return "Value is too large";
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}
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};
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/**
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* \class small_uint
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* \brief Represents a field of <i>n</i> bits.
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*
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* This finds the best integral type of at least <i>n</i> bits and
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* uses it to store the wrapped value.
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*/
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template<size_t n>
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class small_uint {
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private:
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template<bool cond, typename OnTrue, typename OnFalse>
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struct if_then_else {
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typedef OnTrue type;
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};
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template<typename OnTrue, typename OnFalse>
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struct if_then_else<false, OnTrue, OnFalse> {
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typedef OnFalse type;
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};
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template<size_t i>
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struct best_type {
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typedef typename if_then_else<
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(i <= 8),
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uint8_t,
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typename if_then_else<
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(i <= 16),
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uint16_t,
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typename if_then_else<
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(i <= 32),
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uint32_t,
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uint64_t
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>::type
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>::type
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>::type type;
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};
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template<uint64_t base, uint64_t pow>
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struct power {
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static const uint64_t value = base * power<base, pow - 1>::value;
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};
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template<uint64_t base>
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struct power<base, 0> {
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static const uint64_t value = 1;
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};
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public:
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/**
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* The type used to store the value.
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*/
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typedef typename best_type<n>::type repr_type;
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/**
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* The maximum value this class can hold.
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*/
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static const repr_type max_value = power<2, n>::value - 1;
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/**
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* Value initializes the value.
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*/
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small_uint() : value() {}
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/**
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* \brief Copy constructs the stored value.
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*
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* This throws a value_too_large exception if the value provided
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* is larger than max_value.
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*
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* \param val The parameter from which to copy construct.
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*/
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small_uint(repr_type val) {
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if (val > max_value) {
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throw value_too_large();
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}
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value = val;
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}
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/**
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* User defined conversion to repr_type.
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*/
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operator repr_type() const {
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return value;
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}
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private:
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repr_type value;
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};
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} // Tins
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#endif // TINS_SMALL_UINT_H
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