It is still C code, so still compatible with C compilers as well. This
change lets us see more clearly where implicit conversions occur by
making them explicit.
- Any non-externally-visible declarations should be `static`.
- Casting away the `const` qualifier from pointers-to-const is
dangerous. All but one instance of this are now correct. The one
instance where we can't keep `const` is one where toxav code actually
writes to a chunk of memory marked as `const`. This code also assumes
4 byte alignment of data packets. I don't know whether that is a valid
assumption, but it's likely unportable, and *not* obviously correct.
- Replaced empty parameter lists with `(void)` to avoid passing
parameters to it. Empty parameter lists are old style declarations for
unknown number and type of arguments.
- Commented out (as `#if DHT_HARDENING` block) the hardening code that
was never executed.
- Minor style fix: don't use `default` in enum-switches unless the number
of enumerators in the default case is very large. In this case, it was
2, so we want to list them both explicitly to be warned about missing
one if we add one in the future.
- Removed the only two function declarations from nTox.h and put them
into nTox.c. They are not used outside and nTox is not a library.
**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.
tox_shell is a basic secure shell that can be used to control a
computer from any Tox client.
Just run tox_shell and make it add your Tox id.
It's very basic but it works.
iphydf