I want to use the composed async operation
asio::async_connect, and cancel it, possibly between the individual calls to
basic_socket::async_connect which it makes.
In the same manner, I’d like to cancel my own composed async operations (which use
I am not asking how to cancel the non-composed member function
basic_socket::async_connect, for which I could call
The free function is composed, so while calling
cancel on the socket might stop an ongoing
socket::async_connect, it would not stop queued operations.
How do I cancel
In general, how do I cancel composed operations?
How do I cancel custom composed operations? (At least with this third option I could hack in some kind of cancellation token system that can check a flag between “building-block” async operations, but I still can’t use existing composed operations in this case).
To summarize the problem, see this diagram from Robert Leahy’s 2019 CppCon talk:
This shows the issue with
async_write, a composed operation which also has this problem.
Robert Leahy solves this by reimplementing
async_write in a wrapper object which checks a cancellation flag before calling every atomic
async_write_some operation on the underlying stream.
Perhaps this is the solution, but it means that I would have to re-implement every built-in composed asio operation to use this kind of similar wrapper object.
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