Coming IO features in Tango

[Lars Ivar Igesund]

Dear D community

To make the Tango development process more transparent, we will start
announcing new and coming features outside of the release cycle itself.
This may be important changes to Tango, notable feature additions or
particularly exciting compatible libraries. They will be about features
already near-finished or well on the way, to avoid false pretences.

By popular demand, the Tango IO subsystem now exposes a 'stream' oriented
API which will be available in the upcoming release 0.99. Tango streams are
described by InputStream and OutputStream, which are hosted by the existing
Conduit mechanism. Both input and output support the notion of 'filter'
chains: distinct chains of attached streams to manipulate content as it
flows in one direction or the other. In order to avoid the pitfalls of a
purely Decorator-pattern design, these stream chains are fully encapsulated
within the hosting Conduit -- this allows the specific attributes of a
Conduit (such as file seek, or various socket attributes) to be exposed at
all times, instead of trying to force-fit those options into the stream
itself. Thus, streams retain an uncomplicated API with little more than
read, write, copy and flush operations.

Tango has been adjusted in various ways to take advantage of the new
streams, and we'll see further use of that model in later releases.

Further on, we're building an asynchronous I/O library based on Tango's IO
abstractions with notifications sent on completion of I/O events. The plan
for the first stage of development is to have an API capable of delivering
I/O, timer and (possibly) Unix signal events to applications through
delegates. It will be able to efficiently handle large numbers ( i.e.
thousands) of active file descriptors/handles (sockets, pipes, etc.) on all
the platforms that Tango supports. Initially the library will work both on
Windows (using I/O completion ports) and on Linux (using epoll); we will
then provide a Mac OS X and FreeBSD implementation (based on kqueue), and
other platforms if there is enough interest from the community.

During the second stage of development we will build a framework on top of
the asynchronous I/O library that will be able to multiplex I/O jobs using
Tango Fibers (i.e. lightweight or userspace threads). Each fiber waiting
for I/O events will be suspended until the event is received, helping to
avoid consuming excessive resources. The load from each fiber will be
distributed among a pool of threads.

The idea behind both libraries is to be able to efficiently implement
network protocols that are either synchronous (HTTP, SMTP, etc.) and
asynchronous (XMPP, etc.) in nature in both client and server applications.

Contact:
http://www.dsource.org/projects/tango/wiki/Contact 

Signed, 

The Tango Team 

http://www.dsource.org/projects/tango/wiki/Contributors 

----

Tango is a D library providing a cohesive runtime and library for the D
programming language. A feature list can be found on
http://www.dsource.org/projects/tango/wiki/Features