Since we switched temporary_buffer to malloc(), it now longer throws
an exception after running out of memory, which leads to a segfault
when referencing a null buffer.
Move reference counting into the deleter core, instead of relegating it
to a shared_deleter (which has to be allocated) and an external reference
counted (also allocated). This dramatically reduces dynamic allocations.
deleter::share() is causing massive amounts of allocation. First,
since usually a packet's deleter is not a shared_deleter, we need to
allocate that shared_deleter. Second, we need an external reference
count which requires yet another allocation.
Making reference counting part of the deleter class would solve both of
these problems, but we cannot easily do that, since users hold
std::unique_ptr<deleter> which is clearly not sharable.
We could do a massive s/unique_ptr/shared_ptr/ here, but that would have
the side effect of making sharing "too easy" - you simply copy the pointer.
We'd like to keep it explicit.
So to make the change easier, rename the existing unique_ptr<deleter> as
plain "deleter", whereas the old "deleter" becomes deleter::impl:
old name new name
-------- --------
deleter deleter::impl
unique_ptr<deleter> deleter
with exactly the same semantics. A later patch can then add explicit sharing.
