Within the kernel, shared memory and transfer memory facilities exist as
completely different kernel objects. They also have different validity
checking as well. Therefore, we shouldn't be treating the two as the
same kind of memory.
They also differ in terms of their behavioral aspect as well. Shared
memory is intended for sharing memory between processes, while transfer
memory is intended to be for transferring memory to other processes.
This breaks out the handling for transfer memory into its own class and
treats it as its own kernel object. This is also important when we
consider resource limits as well. Particularly because transfer memory
is limited by the resource limit value set for it.
While we currently don't handle resource limit testing against objects
yet (but we do allow setting them), this will make implementing that
behavior much easier in the future, as we don't need to distinguish
between shared memory and transfer memory allocations in the same place.
The previous code had some minor issues with it, really not a big deal,
but amending it is basically 'free', so I figured, "why not?".
With the standard container maps, when:
map[key] = thing;
is done, this can cause potentially undesirable behavior in certain
scenarios. In particular, if there's no value associated with the key,
then the map constructs a default initialized instance of the value
type.
In this case, since it's a std::shared_ptr (as a type alias) that is
the value type, this will construct a std::shared_pointer, and then
assign over it (with objects that are quite large, or actively heap
allocate this can be extremely undesirable).
We also make the function take the region by value, as we can avoid a
copy (and by extension with std::shared_ptr, a copy causes an atomic
reference count increment), in certain scenarios when ownership isn't a
concern (i.e. when ReserveGlobalRegion is called with an rvalue
reference, then no copy at all occurs). So, it's more-or-less a "free"
gain without many downsides.
With this, all kernel objects finally have all of their data members
behind an interface, making it nicer to reason about interactions with
other code (as external code no longer has the freedom to totally alter
internals and potentially messing up invariants).
After doing a little more reading up on the Opus codec, it turns out
that the multistream API that is part of libopus can handle regular
packets. Regular packets are just a degenerate case of multistream Opus
packets, and all that's necessary is to pass the number of streams as 1
and provide a basic channel mapping, then everything works fine for
that case.
This allows us to get rid of the need to use both APIs in the future
when implementing multistream variants in a follow-up PR, greatly
simplifying the code that needs to be written.
Previously this was required, as BitField wasn't trivially copyable.
BitField has since been made trivially copyable, so now this isn't
required anymore.
Relocates the error code to where it's most related, similar to how all
the other error codes are. Previously we were including a non-generic
error in the main result code header.
These can just be passed regularly, now that we use fmt instead of our
old logging system.
While we're at it, make the parameters to MakeFunctionString
std::string_views.
