ivykis is a library for asynchronous I/O readiness notification.
It is a thin, portable wrapper around OS-provided mechanisms such as
ivykis was mainly designed for building high-performance network
applications, but can be used in any event-driven application that
file descriptors as its event sources.
While some programming models dictate using blocking I/O and starting
a thread per event source, programs written to the ivykis API are
generally single-threaded (or use only a small number of threads),
and never block on I/O. All input and output is done in a nonblocking
fashion, with I/O readiness notifications delivered via callback
The two main event sources in ivykis are file descriptors and timers.
File descriptors generate an event when they become readable or
writable or trigger an error condition, while timers generate an event
when the system time increments past a certain pre-set time. Events
associated with file descriptors are level-triggered -- a callback
function set up to handle a certain file descriptor event will be
called repeatedly until the condition generating the event has been
As mentioned, applications using ivykis are generally single-threaded.
Event callbacks are strictly serialised within a thread, and
non-preemptible. This mostly removes the need for locking of shared
data, and generally simplifies writing applications.
Each thread that uses ivykis has its own file descriptors and timers,
and runs a separate event loop.
In ivykis, all code that is not initialization code runs from callback
functions. Callback functions are not allowed to block. If a
particular piece of code wants to perform a certain operation that can
block, it either has to schedule it to run in a separate thread, or it
has to perform the operation in a nonblocking fashion instead. For
example, registering an input callback function instead of blocking
on a read, registering a timer instead of calling
In case of an internal error, ivykis will use
to report the error. The application can provide a custom fatal
error handler by calling