On Sat, 3 Apr 2004, [gb2312] Lei Jin wrote:

> Use "ccc chain" mechanism makes the code seeming uniform. But
> it cause the source code difficult to understand because lots
> of indirect function call and variety of parameters.

The other way is to use threads and mutexes (much more complex
and a bit slower too).


> I wonder whether we can call the target function directly
> instead of using "ccc chain", but I do not know if there is
> difference between these two methods ???

The CCC is not just a way of making function calls, is a theory
that allows for implementing non-preemptive parallelism without
threads or forks.

All the networking and error control in Dillo is driven by
these pseudo-threads each shaped as a dynamic CCC. There can be
even hundreds of them running at the same time (depending on the
page, and on how many pages are loading in the background).

Each thread doing network jobs can linger for a long time
(generally measured in seconds, depending on latency, network
load, size of the transfer, bandwidth etc) --that explains the
need for a parallel approach--, now, each one of those threads
needs independent error control and recovery, and it may have
several steps to perform, so it also has to keep track of its
state.

That's the job of the CCC.

It looks like contrived complexity, for sure, but that's mainly
because people don't even start to realize that it handles
parallelism in a single address space.

This is a bit of my fault, I created the theory while working
on Dillo, but I've never had the time to write it down and
present it in abstract. Priorities always stood in the way.

To my relief, it has worked rock solid, flexible enough to even
account for plugins, and has needed low maintenance.

Beleieve it or not, when things arrive to this state, the
Jargon file regards them as "Deep magic".


Cheers
Jorge.-

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