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// Author: ricab
// Source: https://github.com/ricab/scope_guard
//
// This is free and unencumbered software released into the public domain.
//
// Anyone is free to copy, modify, publish, use, compile, sell, or
// distribute this software, either in source code form or as a compiled
// binary, for any purpose, commercial or non-commercial, and by any
// means.
//
// In jurisdictions that recognize copyright laws, the author or authors
// of this software dedicate any and all copyright interest in the
// software to the public domain. We make this dedication for the benefit
// of the public at large and to the detriment of our heirs and
// successors. We intend this dedication to be an overt act of
// relinquishment in perpetuity of all present and future rights to this
// software under copyright law.
//
// 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 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.
//
// For more information, please refer to <http://unlicense.org>
#ifndef SCOPE_GUARD_HPP_
#define SCOPE_GUARD_HPP_
#include <type_traits>
#include <utility>
#if __cplusplus >= 201703L && defined(SG_REQUIRE_NOEXCEPT_IN_CPP17)
#define SG_REQUIRE_NOEXCEPT
#endif
namespace sg
{
namespace detail
{
/* --- Some custom type traits --- */
// Type trait determining whether a type is callable with no arguments
template<typename T, typename = void>
struct is_noarg_callable_t
: public std::false_type
{}; // in general, false
template<typename T>
struct is_noarg_callable_t<T, decltype(std::declval<T&&>()())>
: public std::true_type
{}; // only true when call expression valid
// Type trait determining whether a no-argument callable returns void
template<typename T>
struct returns_void_t
: public std::is_same<void, decltype(std::declval<T&&>()())>
{};
/* Type trait determining whether a no-arg callable is nothrow invocable if
required. This is where SG_REQUIRE_NOEXCEPT logic is encapsulated. */
template<typename T>
struct is_nothrow_invocable_if_required_t
: public
#ifdef SG_REQUIRE_NOEXCEPT
std::is_nothrow_invocable<T> /* Note: _r variants not enough to
confirm void return: any return can be
discarded so all returns are
compatible with void */
#else
std::true_type
#endif
{};
// logic AND of two or more type traits
template<typename A, typename B, typename... C>
struct and_t : public and_t<A, and_t<B, C...>>
{}; // for more than two arguments
template<typename A, typename B>
struct and_t<A, B> : public std::conditional<A::value, B, A>::type
{}; // for two arguments
// Type trait determining whether a type is a proper scope_guard callback.
template<typename T>
struct is_proper_sg_callback_t
: public and_t<is_noarg_callable_t<T>,
returns_void_t<T>,
is_nothrow_invocable_if_required_t<T>,
std::is_nothrow_destructible<T>>
{};
/* --- The actual scope_guard template --- */
template<typename Callback,
typename = typename std::enable_if<
is_proper_sg_callback_t<Callback>::value>::type>
class scope_guard;
/* --- Now the friend maker --- */
template<typename Callback>
detail::scope_guard<Callback> make_scope_guard(Callback&& callback)
noexcept(std::is_nothrow_constructible<Callback, Callback&&>::value); /*
we need this in the inner namespace due to MSVC bugs preventing
sg::detail::scope_guard from befriending a sg::make_scope_guard
template instance in the parent namespace (see https://is.gd/xFfFhE). */
/* --- The template specialization that actually defines the class --- */
template<typename Callback>
class scope_guard<Callback> final
{
public:
typedef Callback callback_type;
scope_guard(scope_guard&& other)
noexcept(std::is_nothrow_constructible<Callback, Callback&&>::value);
~scope_guard() noexcept; // highlight noexcept dtor
void dismiss() noexcept;
public:
scope_guard() = delete;
scope_guard(const scope_guard&) = delete;
scope_guard& operator=(const scope_guard&) = delete;
scope_guard& operator=(scope_guard&&) = delete;
private:
explicit scope_guard(Callback&& callback)
noexcept(std::is_nothrow_constructible<Callback, Callback&&>::value); /*
meant for friends only */
friend scope_guard<Callback> make_scope_guard<Callback>(Callback&&)
noexcept(std::is_nothrow_constructible<Callback, Callback&&>::value); /*
only make_scope_guard can create scope_guards from scratch (i.e. non-move)
*/
private:
Callback m_callback;
bool m_active;
};
} // namespace detail
/* --- Now the single public maker function --- */
using detail::make_scope_guard; // see comment on declaration above
} // namespace sg
////////////////////////////////////////////////////////////////////////////////
template<typename Callback>
sg::detail::scope_guard<Callback>::scope_guard(Callback&& callback)
noexcept(std::is_nothrow_constructible<Callback, Callback&&>::value)
: m_callback(std::forward<Callback>(callback)) /* use () instead of {} because
of DR 1467 (https://is.gd/WHmWuo), which still impacts older compilers
(e.g. GCC 4.x and clang <=3.6, see https://godbolt.org/g/TE9tPJ and
https://is.gd/Tsmh8G) */
, m_active{true}
{}
////////////////////////////////////////////////////////////////////////////////
template<typename Callback>
sg::detail::scope_guard<Callback>::~scope_guard() noexcept
{
if(m_active)
m_callback();
}
////////////////////////////////////////////////////////////////////////////////
template<typename Callback>
sg::detail::scope_guard<Callback>::scope_guard(scope_guard&& other)
noexcept(std::is_nothrow_constructible<Callback, Callback&&>::value)
: m_callback(std::forward<Callback>(other.m_callback)) // idem
, m_active{std::move(other.m_active)}
{
other.m_active = false;
}
////////////////////////////////////////////////////////////////////////////////
template<typename Callback>
inline void sg::detail::scope_guard<Callback>::dismiss() noexcept
{
m_active = false;
}
////////////////////////////////////////////////////////////////////////////////
template<typename Callback>
inline auto sg::detail::make_scope_guard(Callback&& callback)
noexcept(std::is_nothrow_constructible<Callback, Callback&&>::value)
-> detail::scope_guard<Callback>
{
return detail::scope_guard<Callback>{std::forward<Callback>(callback)};
}
#endif /* SCOPE_GUARD_HPP_ */
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