[Twisted-Python] New C++ implementation of Deferreds

Tom Cocagne tom.cocagne at gmail.com
Thu Jan 29 15:21:36 EST 2009

    The question of whether anyone had developed a C++ implementation of
Twisted's Deferreds has cropped up on this list several times over the last
few years. To date, I've unfortunately been forced to sit on an
implementation I developed several years ago for the Department of Defense.
Due to some rather draconian IP & security policies, it's taken an
exceptionally long time to get the code released. I'm happy to announce
though that I finally managed to obtain release authorization for it and
that the code now has a new home on Sourceforge.

    As C++ has differing language features, the API of the C++ deferreds
isn't identical to those of Twisted's but most of the key concepts mapped
over pretty well. Additionally, this implementation has a few design
extensions to facilitate the development multi-threaded C++ applications.
The multi-threaded aspect grew almost accidentally out of the original
single-threaded design but, since then, it has proven to be extraordinarily
useful for simplifying several multi-threaded applications I've worked on.

    The implementation of the library is, however, rather complex. In large
part, this is due to the effort required to work around the inherent
inflexibility of the C++ type system. The Function, Bind, and
Meta-Programming libraries found in Boost have gone a long way towards
simplify the implementation though (my original Loki-based attempt was
almost incomprehensible even to me ;-). The library is fully documented
though so as long as you're reasonably comfortable with C++ templates, it
should be understandable.

    So far, the library has only been exposed to a handful of individuals
for review. I'd be interested to hear the comments anyone has about the
design and/or implementation approach. The code is available at:



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