std::future_status

std::future_status

Defined in header <future> - 定义于头文件 <future>

1. std::future_status

enum class future_status;

since C++11

enum class future_status {
    ready,
    timeout,
    deferred
};

Specifies state of a future as returned by wait_for and wait_until functions of std::future and std::shared_future.
指定 std::future 和 std::shared_future 的 wait_for 和 wait_until 函数所返回的 future 状态。

Return value for timed future operations - 定时 future 操作的返回值

This enum class type defines the possible return values of the wait_for and wait_until member functions of future and shared_future.
这种枚举类类型定义了 future and shared_future 的 wait_for and wait_until 成员函数的可能返回值。

future_status label	int value	description
future_status::ready	0	The function returned because the shared state was ready. - 共享状态就绪。
future_status::timeout	1	The function returned because the specified time was exhausted. - 共享状态在经过指定的时限时长前仍未就绪。
future_status::deferred	2	The function returned because the shared state contains a deferred function (see std::async). -共享状态含有延迟的函数，故将仅在显式请求时计算结果。

References

http://www.cplusplus.com/reference/future/future_status/
https://en.cppreference.com/w/cpp/thread/future_status