So here's the problem: you can wrap a generator in a chip to create source.
Easy!
But you cannot run a pipeline inside a generator. This is because a generator
is a function closure, which therefore uses the machine stack for the
return address, and fthreads do service requests by simply returning
control to the scheduler. So a pipeline inside a generator or other
function would just return control on the first service call, which would
probably be a spawn_fthread. Nothing would happen even if the typing
was correct.
I am now going to solve this problem, probably in stages.
The first stage will allow you to create a scheduler object, and
spawn fibres to be run by that scheduler.
Such a scheduler object is distinct from the master scheduler.
So you cannot in general use channels which span between schedulers.
However, if you do, interesting things happen. Remember that fthreads
suspended waiting on channel I/O are owned by the channel.
No scheduler knows about them. So if you write on a channel from
a fthread running on the main scheduler, then read on a subsidiary scheduler,
the writer fthread is now lifted to the subsidiary scheduler.
Now, you may ask: how does Felix run procedures inside functions now??
ANSWER: It use a supreme hack! Of course!
It calls a MICRO scheduler:
void run(::flx::rtl::con_t *p)
{
while(p)
{
try { p=p->resume(); }
catch (::flx::rtl::con_t *x) { p = x; }
}
}
This just ignores service requests. It handles procedure calls and
returns but nothing else.
If we replaced this with a subsidiary scheduler we could do channel I/O.
There are consequences! The function cannot return until all the active
threads have run. Remember this doesn't just mean ones spawned
by this function. It also includes any sucked in from the master layer by
using any bridging channels. All hell will break loose if you have a channel
in global scope and use that, because that will probably suck in the whole
mainline :) [Actually I have not thought deeply about this]
Note also my first cut will only do synchronous I/O. You cannot
do async I/O (reading sockets for example).
--
john skaller
skal...@users.sourceforge.net
http://felix-lang.org
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