112 lines
3.0 KiB
C++
112 lines
3.0 KiB
C++
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#ifndef BOOST_NUMERIC_CHECKED_RESULT
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#define BOOST_NUMERIC_CHECKED_RESULT
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// Copyright (c) 2012 Robert Ramey
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// contains operations for doing checked aritmetic on NATIVE
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// C++ types.
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#include <cassert>
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#include <type_traits> // is_convertible
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#include "exception.hpp"
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namespace boost {
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namespace safe_numerics {
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template<typename R>
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struct checked_result {
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const safe_numerics_error m_e;
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union contents {
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R m_r;
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char const * const m_msg;
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// contstructors for different types
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constexpr contents(const R & r) noexcept : m_r(r){}
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constexpr contents(char const * msg) noexcept : m_msg(msg) {}
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constexpr operator R () noexcept {
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return m_r;
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}
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constexpr operator char const * () noexcept {
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return m_msg;
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}
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};
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contents m_contents;
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// don't permit construction without initial value;
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checked_result() = delete;
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checked_result(const checked_result & r) = default;
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checked_result(checked_result && r) = default;
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constexpr /*explicit*/ checked_result(const R & r) noexcept :
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m_e(safe_numerics_error::success),
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m_contents{r}
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{}
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constexpr /*explicit*/ checked_result(
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const safe_numerics_error & e,
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const char * msg = ""
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) noexcept :
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m_e(e),
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m_contents{msg}
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{
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assert(m_e != safe_numerics_error::success);
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}
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// permit construct from another checked result type
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template<typename T>
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constexpr /*explicit*/ checked_result(const checked_result<T> & t) noexcept :
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m_e(t.m_e)
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{
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static_assert(
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std::is_convertible<T, R>::value,
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"T must be convertible to R"
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);
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if(safe_numerics_error::success == t.m_e)
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m_contents.m_r = t.m_r;
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else
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m_contents.m_msg = t.m_msg;
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}
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constexpr bool exception() const {
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return m_e != safe_numerics_error::success;
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}
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// accesors
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constexpr operator R() const noexcept{
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// don't assert here. Let the library catch these errors
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// assert(! exception());
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return m_contents.m_r;
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}
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constexpr operator safe_numerics_error () const noexcept{
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// note that this is a legitimate operation even when
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// the operation was successful - it will return success
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return m_e;
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}
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constexpr operator const char *() const noexcept{
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assert(exception());
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return m_contents.m_msg;
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}
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// disallow assignment
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checked_result & operator=(const checked_result &) = delete;
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}; // checked_result
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template <class R>
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class make_checked_result {
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public:
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template<safe_numerics_error E>
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constexpr static checked_result<R> invoke(
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char const * const & m
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) noexcept {
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return checked_result<R>(E, m);
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}
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};
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} // safe_numerics
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} // boost
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#endif // BOOST_NUMERIC_CHECKED_RESULT
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