Dex

Dex provides Future-based programming for GLib-based applications.

It both integrates with and brings new features for application and library authors who want to structure concurrent code in an easy to manage way.

Dex also provides Fibers which allow writing synchronous looking code in C that uses asynchronous and future-based APIs.

Dex is licensed as LGPL-2.1+.

Documentation

You can find documentation for Dex updated as part of the CI pipeline.

Building

Dex requires GLib 2.68 or newer but can likely be ported to older versions. For those interested, you can add missing API to dex-compat-private.h.

Some examples require additional libraries but will not be compiled if the libraries are unavailable while building.

Use Meson to build the project.

$ cd libdex/
$ meson setup build . --prefix=/usr
$ cd build/
$ ninja
$ ninja test

You can build for Windows using mingw which is easy on Fedora Linux.

$ sudo dnf install mingw64-gcc mingw64-glib2
$ cd libdex/
$ meson setup build-win64 . --cross-file=/usr/share/mingw/toolchain-mingw64.meson
$ cd build/
$ ninja

# You can test using wine, but will need access to libraries
$ cd /usr/x86_64-w64-mingw32/sys-root/mingw/bin/
$ wine $builddir/examples/tcp-echo.exe

Supported Platforms

• Linux
• macOS
• FreeBSD
• Windows
• Illumos

More Information

You can read about why this is being created and what led to it over the past two decades of contributing to GNOME and GTK.

• https://blogs.gnome.org/chergert/2022/11/24/concurrency-parallelism-i-o-scheduling-thread-pooling-and-work-stealing/
• https://blogs.gnome.org/chergert/2022/12/13/threading-fibers/
• https://blogs.gnome.org/chergert/2022/12/16/dex-examples-and-windows-support/

Implementation Notes

While Dex is using GObject and GIO, it implements it's own fundamental type (DexObject) for which all other types inherit. Given the concurrent and parallel nature of futures and the many situations to support, it is the authors opinion that the performance drawbacks of such a flexible type as GObject is too costly. By controlling the feature-set to strictly what is necessary we can avoid much of the slow paths in GObject.

You wont notice much of a difference though, as types are generally defined and used very similarly to GObject's but with different macro names.

You can see this elsewhere in both GStreamer and GTK 4's render nodes.

Terminology

• Future describes something that can either resolve (succeed) or reject (fail) now or in the future. It's resolved/rejected value is immutable after completing.
• Resolved indicates that a future has completed successfully and provided a value which can be read by the consumer.
• Rejected indicates that a future has completed with failure and provided an error which can be read by the consumer.
• Promise is a Future that allows user code to set the resolved or rejected value once.