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.