Source

`stdlib/memory/mode.hpp`

2// Original work; see ACKNOWLEDGMENTS.md for the open-source ideas we build upon.

3#pragma once

5/**

6 * @file mode.hpp

7 * @brief `memory` access-mode tags: `read`, `write`, `write_renewable`, and the `Mode` concept.

8 *

9 * Empty tag types that select a `Lease`'s mode at compile time (dispatch on type, zero storage).

10 * Lowercase because they are tags/markers, not classes (cf. `std::in_place_t`); a cheatah user

11 * spells them `memory.read` / `memory.write`.

12 */

14#include <type_traits>

16namespace cheatah::memory {

struct read {};             ///< a shared, read-only lease (readers coexist — `std::shared_lock`-flavored, but no lock object is held).

struct write {};            ///< an exclusive, one-shot write lease (a writer is alone — `std::unique_lock`-flavored, but no lock object is held).

20struct write_renewable {}; ///< an exclusive write lease that MAY re-lease — a distinct, visible smell.

22/// The lease-mode concept — every `Lease`/`Request` template is constrained to one of the three tags

23/// (per the project's constrain-all-templates policy).

24template <class M>

25concept Mode = std::is_same_v<M, read> || std::is_same_v<M, write> || std::is_same_v<M, write_renewable>;

27/// True for the two exclusive (write) modes.

28template <class M>

29inline constexpr bool is_write_mode = std::is_same_v<M, write> || std::is_same_v<M, write_renewable>;

31} // namespace cheatah::memory