Messenger is slightly twisty when it comes to sending connection status
callbacks It will very likely need at the very least a partial refactor to
clean it up a bit. Toxcore shouldn't need void *userdata as deep as is
currently does.
(amend 1) Because of the nature of toxcore connection callbacks, I decided to
change this commit from statelessness for connections changes to statelessness
for friend requests. It's simpler this was and doesn't include doing anything
foolish in the time between commits.
group fixup because grayhatter doesn't want to do it
"arguably correct" is not how you write security sensitive code
Clear a compiler warning about types within a function.
Also, no longer #include the group code into tox.c. Instead, compile it
separately in tox_group.c. This is a bit less surprising to someone looking
around the code. Having some implementations in a .h file is certainly a bit
surprising to a disciplined C programmer, especially when there is no technical
reason to do it.
This removes the global logger (which by the way was deleted when the first tox
was killed, so other toxes would then stop logging). Various bits of the code
now carry a logger or pass it around. It's a bit less transparent now, but now
there is no need to have a global logger, and clients can decide what to log and
where.
**What are we doing?**
We are moving towards stateless callbacks. This means that when registering a
callback, you no longer pass a user data pointer. Instead, you pass a user data
pointer to tox_iterate. This pointer is threaded through the code, passed to
each callback. The callback can modify the data pointed at. An extra indirection
will be needed if the pointer itself can change.
**Why?**
Currently, callbacks are registered with a user data pointer. This means the
library has N pointers for N different callbacks. These pointers need to be
managed by the client code. Managing the lifetime of the pointee can be
difficult. In C++, it takes special effort to ensure that the lifetime of user
data extends at least beyond the lifetime of the Tox instance. For other
languages, the situation is much worse. Java and other garbage collected
languages may move objects in memory, so the pointers are not stable. Tox4j goes
through a lot of effort to make the Java/Scala user experience a pleasant one by
keeping a global array of Tox+userdata on the C++ side, and communicating via
protobufs. A Haskell FFI would have to do similarly complex tricks.
Stateless callbacks ensure that a user data pointer only needs to live during a
single function call. This means that the user code (or language runtime) can
move the data around at will, as long as it sets the new location in the
callback.
**How?**
We are doing this change one callback at a time. After each callback, we ensure
that everything still works as expected. This means the toxcore change will
require 15 Pull Requests.
