Crate nano_ecs

Nano-ECS

A bare-bones macro-based Entity-Component-System

• Maximum 64 components per entity
• Stores components sequentially in same array
• Masks for enabled/disabled components

use nano_ecs::*;

#[derive(Clone)]
pub struct Position(pub f32);
#[derive(Clone)]
pub struct Velocity(pub f32);

ecs!{4: Position, Velocity}

fn main() {
    let mut world = World::new();
    world.push(Position(0.0));
    world.push((Position(0.0), Velocity(0.0)));
    let dt = 1.0;
    system!(world, |pos: &mut Position, vel: &Velocity| {
        pos.0 = pos.0 + vel.0 * dt;
    });
}

Design

The ecs! macro generates a World and Component object.

Can be used with any Rust data structure that implements Clone.

The order of declared components is used to assign every component an index. This index is used in the mask per entity and to handle slice memory correctly.

• All components are stored in one array inside World.
• All entities have a slice refering to components
• All entities have a mask that enable/disable components

Macros

ecs	Creates an Entity-Component-System.
entity	Accesses a single entity.
entity_access	Accesses an entity.
entity_ids	Enumerates indices of entities only.
entity_unchecked_access	Accesses an entity, but without checking active mask.
ind	Generates Ind impl for Component.
mask_pat	Generates mask pattern based on a set of components.
mask_pre	Used internally by other macros.
push	Generates Push impl for World.
push_impl	Calls push macro with smaller arguments.
system	Declares and executes a system.
system_ids	Same as system!, but with entity ids.
tup_count	Helper macro for counting size of a tuple.

Structs

MaskStorage

Stores masks efficiently and allows fast iteration.