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///////////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
//
// This code is licensed under the MIT License (MIT).
//
// 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 GSL_UTIL_H
#define GSL_UTIL_H
#include <gsl/gsl_assert> // for Expects
#include <array>
#include <cstddef> // for ptrdiff_t, size_t
#include <exception> // for exception
#include <initializer_list> // for initializer_list
#include <type_traits> // for is_signed, integral_constant
#include <utility> // for forward
#if defined(_MSC_VER)
#pragma warning(push)
#pragma warning(disable : 4127) // conditional expression is constant
#if _MSC_VER < 1910
#pragma push_macro("constexpr")
#define constexpr /*constexpr*/
#endif // _MSC_VER < 1910
#endif // _MSC_VER
namespace gsl
{
//
// GSL.util: utilities
//
// final_action allows you to ensure something gets run at the end of a scope
template <class F>
class final_action
{
public:
explicit final_action(F f) noexcept : f_(std::move(f)), invoke_(true) {}
final_action(final_action&& other) noexcept : f_(std::move(other.f_)), invoke_(other.invoke_)
{
other.invoke_ = false;
}
final_action(const final_action&) = delete;
final_action& operator=(const final_action&) = delete;
~final_action() noexcept
{
if (invoke_) f_();
}
private:
F f_;
bool invoke_;
};
// finally() - convenience function to generate a final_action
template <class F>
inline final_action<F> finally(const F& f) noexcept
{
return final_action<F>(f);
}
template <class F>
inline final_action<F> finally(F&& f) noexcept
{
return final_action<F>(std::forward<F>(f));
}
// narrow_cast(): a searchable way to do narrowing casts of values
template <class T, class U>
inline constexpr T narrow_cast(U&& u) noexcept
{
return static_cast<T>(std::forward<U>(u));
}
struct narrowing_error : public std::exception
{
};
namespace details
{
template <class T, class U>
struct is_same_signedness
: public std::integral_constant<bool, std::is_signed<T>::value == std::is_signed<U>::value>
{
};
}
// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
template <class T, class U>
inline T narrow(U u)
{
T t = narrow_cast<T>(u);
if (static_cast<U>(t) != u) throw narrowing_error();
if (!details::is_same_signedness<T, U>::value && ((t < T{}) != (u < U{})))
throw narrowing_error();
return t;
}
//
// at() - Bounds-checked way of accessing builtin arrays, std::array, std::vector
//
template <class T, std::size_t N>
inline constexpr T& at(T (&arr)[N], const std::ptrdiff_t index)
{
Expects(index >= 0 && index < narrow_cast<std::ptrdiff_t>(N));
return arr[static_cast<std::size_t>(index)];
}
template <class Cont>
inline constexpr auto at(Cont& cont, const std::ptrdiff_t index) -> decltype(cont[cont.size()])
{
Expects(index >= 0 && index < narrow_cast<std::ptrdiff_t>(cont.size()));
using size_type = decltype(cont.size());
return cont[static_cast<size_type>(index)];
}
template <class T>
inline constexpr T at(const std::initializer_list<T> cont, const std::ptrdiff_t index)
{
Expects(index >= 0 && index < narrow_cast<std::ptrdiff_t>(cont.size()));
return *(cont.begin() + index);
}
} // namespace gsl
#if defined(_MSC_VER)
#if _MSC_VER < 1910
#undef constexpr
#pragma pop_macro("constexpr")
#endif // _MSC_VER < 1910
#pragma warning(pop)
#endif // _MSC_VER
#endif // GSL_UTIL_H
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