ECS in C89

A simple Entity Component System implementation in C89. My implementation is a basic introductory ECS with a few of my own ideas and approaches, though not in a real 'production' project setting. This simple demo is not a 1-to-1 of how i would do everything in a production project. For further production / real scenario details, read the source comments with the 'In real:' prefix.

Building information

The project depends only on SDL3 for two (2) important reasons:

• To showcase abstracting a pre-existing API and object (struct) into a component
• Show something more interesting than some console output

It is required you have SDL3 and the relevant pkg-config to build the project. If you are using MSVC for some reason, and want to build the project, create a solution and set up your SDL3 dependency in your PATH manually.

Source overview

What is the Component API?

• It is the API a given component uses to implement its functionality, it does not include the map.h utility, just component.h.

  exposed in : inc/ecs/component.h implemented in : src/ecs.c

What is the Entity API?

• It is the API that allows registration/unregistration of entities.

  exposed in : inc/ecs/entity.h implemented in : src/ecs.c

Individual components can be found in the components/ folders in src/ and inc/. Some rendering related code lives in the renderer folders in src/ and inc/. Finally, I decided for project simplicity to keep map.h in the inc/ecs/ folder, and be implemented in src/map.c.

Some things about my implementation

Everything is in the .bss segment as static globals, but the system contains a stub (FreeECS) and unregistration mechanism for freeing system and component related memory. My map implementation maps an ID to a structure using two 1D arrays (one ID array, and one struct array), which are provided by the API User. ID generation uses the Splitmix64 algorithm, because it has very good bit coverage. Usually bit coverage does not matter too much, but ECSs can be used for very intensive tasks with many entities.

Cool facts

Running find . -name "*.c" -o -name "*.h" | xargs wc -l, the whole project is around ~500 significant lines. A simple component can be around ~40 lines, the system itself is suprisingly smaller than the map implementation and rendering code too.

Running size app -A gives us a good idea of how much memory the globals take. .bss is the largest section, because around ~4 mb is utilized by the entity registry.

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Enjoy! - temple-fed | License : GPL3 (See LICENSE file)