The asio::config class provides access to configuration variables that
are associated with an execution context. The class is intended for use
by asio internals, or by libraries or user-provided abstractions that
build on top of asio. These configuration variables will typically be
used to fine tune behaviour, such as enabling or disabling certain
optimisations.
When constructing an execution context, such as an io_context, the
caller may optionally pass a service_maker to install a concrete
configuration service into the context. For example:
asio::io_context ctx{asio::config_from_env{}};
The configuration variables' values are accessed by using the
asio::config class, passing a section, key and default value:
asio::config cfg{ctx};
bool enable_locking = cfg.get("scheduler", "locking", true);
The initial set of configuration variables recognised by the asio
internals correspond to the concurrency hint and its special values:
"scheduler" / "concurrency_hint" (int)
"scheduler" / "locking" (bool)
"reactor" / "registration_locking" (bool)
"reactor" / "io_locking" (bool)
