How to check if a std::async task is finished?

Question

In my graphics application I want to generate a batch meshes in another thread. Therefore I asynchrony call the member function using std::async.

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Answer 1

Use future::wait_for(). You can specify a timeout, and after that, get a status code.

Example:

task.wait_for(std::chrono::seconds(1));

This will return future_status::ready, future_status::deferred or future_status::timeout, so you know the operation's status. You can also specify a timeout of 0 to have the check return immediately as soon as possible.

Answer 2

There's an is_ready member function in the works for std::future. In the meantime, the VC implementation has an _Is_ready() member.