Note that this is a work in progress and simply a first attempt at
getting some code into place before being able to test it. This code
follows of sorts both the poll and epoll sections of the codebase hoping
to achieve the exact same.
A threaded abstract is an abstract type that can be freely shared
between threads. While no synchronization is provided, refcounting
and transport between threads is. This will let implementers more easily
exploit OS-level parallelism in C library code. The caveat with these
types is that they need to be careful in how they interact with objects
on other heaps.
Introduces close semtantics to channels as well, but otherwise
threaded channels behave much like non-threaded channels. They have
different marshalling behavior though, and can only send values over by
packing and unpacking them. For now, this means only primitive values
although this will be expanded.
Also missing some implementation for closing threaded channels, and a
whole lot of testing. Achtung!, Caveat emptor, here be dragons and bugs.
This would allow an embedder to suspend the current Janet fiber
via an external event like a signal, other thread, or really anything.
This is a useful primitive for custom schedulers that would call
janet_interpreter_interupt periodically (say, in an interval with SIG_ALRM),
do some work, and then use janet_continue on the janet_root_fiber, or
for embedding into other soft-realtime applications like a game. To say,
only allow about 5ms per frame of interpreter time.
Before, these bindings we just ignored. However, it useful for
controlling janet_printf and janet_eprintf, for example. These can
be called from C code without being inside a call to janet_continue.
This makes these operatios use constant stack space rather
than linear stackspace given the size of the inputs. This is important
to prevent certain parser input from causing a stack overflow - in
general, we try to avoid unbounded recursion.
Required a few changes to APIs, namely janet_root_fiber()
to get topmost fiber that is active in the current scheduler.
This is distinct from janet_current_fiber(), which gets the bottom
most fiber in the fiber stack - it might have a parent, and so cannot
be reliably resumed.
This is the kind of situation that makes symmetric coroutines more
attractive.
This way we can support fewer build configurations. Also, remove
all undefined behavior due to use of memcpy with NULL pointers. GCC
was exploiting this to remove NULL checks in some builds.
Also make integer to size_t casts explicit rather than relying on
int32_t * sizeof(x) = size_t. This is kind of a personal preference for
this problem.
Rather than messing with janet_core_dictionary, we
instead cache the core enevironment, and pull out the
needed tables from there. This is more flexible, more correct, and
also exposes janet_resolve_core, which can be easily used from the C
API.
Calvin Rose