All I/O objects now have an additional Executor template parameter. This
template parameter defaults to the asio::executor type (the polymorphic
executor wrapper) but can be used to specify a user-defined executor
type.
I/O objects' constructors and functions that previously took an
asio::io_context& now accept either an Executor or a reference to a
concrete ExecutionContext (such as asio::io_context or
asio::thread_pool).
One potential point of breakage in existing user code is when reusing an
I/O object's io_context for constructing another I/O object, as in:
asio::steady_timer my_timer(my_socket.get_executor().context());
To fix this, either construct the second I/O object using the first I/O
object's executor:
asio::steady_timer my_timer(my_socket.get_executor());
or otherwise explicitly pass the io_context:
asio::steady_timer my_timer(my_io_context);
N.B. The Windows-specific tick_count_timer example has been removed as
it has been superseded by timers based on the standard steady_clock.
It's also not clear how to map a wrapping time source to the standard
chrono concepts.
Define BOOST_ASIO_USE_BOOST_DATE_TIME_FOR_SOCKET_IOSTREAM to enable the
old Boost.Date_Time interface in basic_socket_streambuf and
basic_socket_iostream.
* Use asio::steady_timer rather than asio::deadline_timer.
* Use asio::dynamic_buffer rather than asio::streambuf.
* Use timed asio::io_context::run_for() function for blocking clients.
* Add example showing a custom completion token for blocking with timeouts.
