By storing the reference in the DCB, the two-way dependency between the
listeners and services is severed. Now the services have no direct link to
listeners and after the destruction of a listener it will be freed once
all connections through it have closed.
Due to the fact that a listener itself has a DCB that must point to a
valid listener, a self-reference is stored in the listener DCB. This is
extremely confusing and is only here to keep the code functional until the
DCB part of the listener can be factored out.
Allocating DCB with new allows the use of C++ objects in the DCB
struct. Also the explicit poll field can be replaced by inheriting from
MXB_POLL_DATA.
Modified the functions to use a listener instead of a DCB in the accepting
process. This removes some of the dependenices that the listeners have on
the DCB system.
By loading the entry points required by a DCB when the Listener is
created, the extra cost of finding the module is removed. It also
simplifies DCB creation by removing the possibility of all failures to
load modules at DCB creation time.
By storing a shared pointer to the listeners in the services, they will be
available as long as the service using them exists. This enables clean
destruction of listeners that still have open sessions.
The listener creation code now separately creates the listener and links
it to the service. Also replaced relevant parts of the related code with
the listener implemented versions of it.
The value would otherwise be assigned outside of it and in some cases not
at all. Now all DCBs (apart from internal ones) have a valid SERVICE
pointer.
The SERV_LISTENER pointer should not be in the DCBs but in the
session. This way the listener is an attribute of a session instead of a
connection. If this is implemented, the authenticator data can be more
easily shared.
Replaced raw pointers in function parameter with const SListener
references. This removes the need to pass raw pointers as arguments and
all access is done via smart pointers.
The iteration of listeners is now done via the global list of
listeners. This removes the need to have a service before a listener is
accessed which also reflects how the actual configuration is laid out. It
also guarantees that any results returned by the find functions will be
valid as long as the results are used.
The listeners are now stored in their own list which allows them to be a
component separate from the service. The next step is to remove the
listener iterator functionality and replace it with its STL counterpart.
