Make entity::index non max

assets/scenes/load_scene_example.scn.ron

@@ -5,7 +5,7 @@
     ),
   },
   entities: {
-    4294967296: (
+    4294967297: (
       components: {
         "bevy_ecs::name::Name": "joe",
         "bevy_transform::components::global_transform::GlobalTransform": ((1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0)),
@@ -23,7 +23,7 @@
         ),
       },
     ),
-    4294967297: (
+    4294967298: (
       components: {
         "scene::ComponentA": (
           x: 3.0,
@@ -32,4 +32,4 @@
       },
     ),
   },
-)
+)

benches/Cargo.toml

@@ -32,6 +32,7 @@ bevy_platform = { path = "../crates/bevy_platform", default-features = false, fe
 glam = "0.29"
 rand = "0.8"
 rand_chacha = "0.3"
+nonmax = { version = "0.5", default-features = false }
 
 # Make `bevy_render` compile on Linux with x11 windowing. x11 vs. Wayland does not matter here
 # because the benches do not actually open any windows.

benches/benches/bevy_ecs/world/entity_hash.rs

@@ -17,9 +17,10 @@ fn make_entity(rng: &mut impl Rng, size: usize) -> Entity {
     let generation = 1.0 + -(1.0 - x).log2() * 2.0;
 
     // this is not reliable, but we're internal so a hack is ok
-    let bits = ((generation as u64) << 32) | (id as u64);
+    let id = id as u64 + 1;
+    let bits = ((generation as u64) << 32) | id;
     let e = Entity::from_bits(bits);
-    assert_eq!(e.index(), id as u32);
+    assert_eq!(e.index(), !(id as u32));
     assert_eq!(e.generation(), generation as u32);
     e
 }

benches/benches/bevy_ecs/world/world_get.rs

@@ -1,9 +1,10 @@
 use core::hint::black_box;
+use nonmax::NonMaxU32;
 
 use bevy_ecs::{
     bundle::{Bundle, NoBundleEffect},
     component::Component,
-    entity::Entity,
+    entity::{Entity, EntityRow},
     system::{Query, SystemState},
     world::World,
 };
@@ -53,7 +54,9 @@ pub fn world_entity(criterion: &mut Criterion) {
 
             bencher.iter(|| {
                 for i in 0..entity_count {
-                    let entity = Entity::from_raw(i);
+                    let entity =
+                        // SAFETY: Range is exclusive.
+                        Entity::from_raw(EntityRow::new(unsafe { NonMaxU32::new_unchecked(i) }));
                     black_box(world.entity(entity));
                 }
             });
@@ -74,7 +77,9 @@ pub fn world_get(criterion: &mut Criterion) {
 
             bencher.iter(|| {
                 for i in 0..entity_count {
-                    let entity = Entity::from_raw(i);
+                    let entity =
+                        // SAFETY: Range is exclusive.
+                        Entity::from_raw(EntityRow::new(unsafe { NonMaxU32::new_unchecked(i) }));
                     assert!(world.get::<Table>(entity).is_some());
                 }
             });
@@ -84,7 +89,9 @@ pub fn world_get(criterion: &mut Criterion) {
 
             bencher.iter(|| {
                 for i in 0..entity_count {
-                    let entity = Entity::from_raw(i);
+                    let entity =
+                        // SAFETY: Range is exclusive.
+                        Entity::from_raw(EntityRow::new(unsafe { NonMaxU32::new_unchecked(i) }));
                     assert!(world.get::<Sparse>(entity).is_some());
                 }
             });
@@ -106,7 +113,9 @@ pub fn world_query_get(criterion: &mut Criterion) {
 
             bencher.iter(|| {
                 for i in 0..entity_count {
-                    let entity = Entity::from_raw(i);
+                    let entity =
+                        // SAFETY: Range is exclusive.
+                        Entity::from_raw(EntityRow::new(unsafe { NonMaxU32::new_unchecked(i) }));
                     assert!(query.get(&world, entity).is_ok());
                 }
             });
@@ -131,7 +140,9 @@ pub fn world_query_get(criterion: &mut Criterion) {
 
             bencher.iter(|| {
                 for i in 0..entity_count {
-                    let entity = Entity::from_raw(i);
+                    let entity =
+                        // SAFETY: Range is exclusive.
+                        Entity::from_raw(EntityRow::new(unsafe { NonMaxU32::new_unchecked(i) }));
                     assert!(query.get(&world, entity).is_ok());
                 }
             });
@@ -142,7 +153,9 @@ pub fn world_query_get(criterion: &mut Criterion) {
 
             bencher.iter(|| {
                 for i in 0..entity_count {
-                    let entity = Entity::from_raw(i);
+                    let entity =
+                        // SAFETY: Range is exclusive.
+                        Entity::from_raw(EntityRow::new(unsafe { NonMaxU32::new_unchecked(i) }));
                     assert!(query.get(&world, entity).is_ok());
                 }
             });
@@ -169,7 +182,10 @@ pub fn world_query_get(criterion: &mut Criterion) {
 
                 bencher.iter(|| {
                     for i in 0..entity_count {
-                        let entity = Entity::from_raw(i);
+                        // SAFETY: Range is exclusive.
+                        let entity = Entity::from_raw(EntityRow::new(unsafe {
+                            NonMaxU32::new_unchecked(i)
+                        }));
                         assert!(query.get(&world, entity).is_ok());
                     }
                 });

crates/bevy_ecs/src/entity/map_entities.rs

@@ -171,7 +171,7 @@ impl<T: MapEntities, A: smallvec::Array<Item = T>> MapEntities for SmallVec<A> {
 ///     fn get_mapped(&mut self, entity: Entity) -> Entity {
 ///         self.map.get(&entity).copied().unwrap_or(entity)
 ///     }
-///     
+///
 ///     fn set_mapped(&mut self, source: Entity, target: Entity) {
 ///         self.map.insert(source, target);
 ///     }
@@ -228,7 +228,7 @@ impl EntityMapper for SceneEntityMapper<'_> {
 
         // this new entity reference is specifically designed to never represent any living entity
         let new = Entity::from_raw_and_generation(
-            self.dead_start.index(),
+            self.dead_start.row(),
             IdentifierMask::inc_masked_high_by(self.dead_start.generation, self.generations),
         );
 
@@ -331,21 +331,19 @@ impl<'m> SceneEntityMapper<'m> {
 
 #[cfg(test)]
 mod tests {
+
     use crate::{
         entity::{Entity, EntityHashMap, EntityMapper, SceneEntityMapper},
         world::World,
     };
 
     #[test]
     fn entity_mapper() {
-        const FIRST_IDX: u32 = 1;
-        const SECOND_IDX: u32 = 2;
-
         let mut map = EntityHashMap::default();
         let mut world = World::new();
         let mut mapper = SceneEntityMapper::new(&mut map, &mut world);
 
-        let mapped_ent = Entity::from_raw(FIRST_IDX);
+        let mapped_ent = Entity::from_raw_u32(1).unwrap();
         let dead_ref = mapper.get_mapped(mapped_ent);
 
         assert_eq!(
@@ -354,7 +352,7 @@ mod tests {
             "should persist the allocated mapping from the previous line"
         );
         assert_eq!(
-            mapper.get_mapped(Entity::from_raw(SECOND_IDX)).index(),
+            mapper.get_mapped(Entity::from_raw_u32(2).unwrap()).index(),
             dead_ref.index(),
             "should re-use the same index for further dead refs"
         );
@@ -372,7 +370,7 @@ mod tests {
         let mut world = World::new();
 
         let dead_ref = SceneEntityMapper::world_scope(&mut map, &mut world, |_, mapper| {
-            mapper.get_mapped(Entity::from_raw(0))
+            mapper.get_mapped(Entity::from_raw_u32(0).unwrap())
         });
 
         // Next allocated entity should be a further generation on the same index