| 1 | // Copyright (C) Microsoft Corporation. All rights reserved. |
| 2 | |
| 3 | #pragma once |
| 4 | |
| 5 | #include <optional> |
| 6 | #include <mutex> |
| 7 | #include <condition_variable> |
| 8 | |
| 9 | /** |
| 10 | * @brief Class that contains a value T that can contain a single value and |
| 11 | * blocks until post or get can be satisfied. |
| 12 | * |
| 13 | * @tparam Value stored in this class. |
| 14 | */ |
| 15 | template <typename T> |
| 16 | struct WaitableValue |
| 17 | { |
| 18 | public: |
| 19 | /** |
| 20 | * @brief Store value the value. Blocks until the value can be stored. |
| 21 | * |
| 22 | * @param[in] value Value to be stored. |
| 23 | */ |
| 24 | void post(T& value) |
| 25 | { |
| 26 | std::unique_lock lck(m_mtx); |
| 27 | while (m_value.has_value()) |
| 28 | { |
| 29 | m_cv.wait(lck); |
| 30 | } |
| 31 | m_value = value; |
| 32 | m_cv.notify_all(); |
| 33 | } |
| 34 | |
| 35 | /** |
| 36 | * @brief Retrieve the value. Blocks until a value is available. |
| 37 | * |
| 38 | * @return Value that was previously stored. |
| 39 | */ |
| 40 | T get() |
| 41 | { |
| 42 | std::unique_lock lck(m_mtx); |
| 43 | while (!m_value.has_value()) |
| 44 | { |
| 45 | m_cv.wait(lck); |
| 46 | } |
| 47 | auto return_value = m_value.value(); |
| 48 | m_value.reset(); |
| 49 | m_cv.notify_all(); |
| 50 | return return_value; |
| 51 | } |
| 52 | |
| 53 | /** |
| 54 | * @brief Attempt to retrieve the value with timeout. |
| 55 | * |
| 56 | * @param[in] timeout Duration to wait before returning empty. |
| 57 | * @return Either the value or a std::nullopt on timeout. |
| 58 | */ |
| 59 | template <typename duration> |
| 60 | std::optional<T> try_get(duration timeout) |
| 61 | { |
| 62 | std::unique_lock lck(m_mtx); |
| 63 | while (!m_value.has_value()) |
| 64 | { |
| 65 | if (m_cv.wait_for(lck, timeout) == std::cv_status::timeout) |
| 66 | { |
| 67 | return std::nullopt; |
| 68 | } |
| 69 | } |
| 70 | auto return_value = m_value.value(); |
| 71 | m_value.reset(); |
| 72 | m_cv.notify_all(); |
| 73 | return {return_value}; |
| 74 | } |
| 75 | |
| 76 | private: |
| 77 | std::mutex m_mtx; |
| 78 | std::condition_variable m_cv; |
| 79 | std::optional<T> m_value; |
| 80 | }; |