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/*
* This source code is released into the public domain.
*/
module;
#include <concepts>
#include <functional>
#include <optional>
#include <utility>
export module nihil.guard;
namespace nihil {
/*
* guard: invoke a callable when this object is destroyed; this is similar to
* scope_exit from the library fundamentals TS, which LLVM doesn't implement.
*/
export template<std::invocable F>
struct guard final {
// Initialise the guard with a callable we will invoke later.
guard(F func) : m_func(std::move(func)) {}
/*
* We are being destroyed, so call the callable.
* If the callable throws, std::terminate() will be called.
*/
~guard()
{
if (m_func)
std::invoke(*m_func);
}
// Release the guard. This turns the destructor into a no-op.
auto release(this guard &self) noexcept -> void
{
self.m_func.reset();
}
// Not default-constructible, movable or copyable.
guard() = delete;
guard(guard const &) = delete;
guard(guard &&) noexcept = delete;
auto operator=(this guard &, guard const &) -> guard & = delete;
auto operator=(this guard &, guard &&) noexcept -> guard & = delete;
private:
// The callable to be invoked when we are destroyed.
std::optional<F> m_func;
};
} // namespace nihil
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