khora_data/ecs/
entity.rs

1// Copyright 2025 eraflo
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::collections::HashMap;
16
17use crate::ecs::{page::PageIndex, SemanticDomain};
18
19/// Represents the central record for an entity, acting as a "table of contents"
20/// that points to the physical location of its component data across various `ComponentPage`s.
21#[derive(Debug, Clone, Default)]
22pub struct EntityMetadata {
23    /// A map from a semantic domain to the location of the component data for that domain.
24    /// This allows an entity to have component data in multiple different pages,
25    /// each specialized for a specific domain (e.g., Spatial, Render).
26    pub(crate) locations: HashMap<SemanticDomain, PageIndex>,
27}
28
29/// A unique identifier for an entity in the world.
30///
31/// It combines an index with a generation count to solve the "ABA problem".
32/// When an entity is despawned, its index can be recycled for a new entity,
33/// but the generation is incremented. This ensures that old `EntityId` handles
34/// pointing to a recycled index become invalid and cannot accidentally affect
35/// the new entity.
36#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
37pub struct EntityId {
38    /// The index of the entity's metadata in the central `Vec<EntityMetadata>`.
39    pub index: u32,
40    /// A generation counter that is incremented each time the index is recycled.
41    pub generation: u32,
42}
khora_data/ecs/entity.rs

khora_data/ecs/
entity.rs
