ecs: add not filter, improve the code for inserting components into entity, bundle cleanup and improvements

lyra-ecs/src/archetype.rs

@@ -1,6 +1,6 @@
 use std::{ptr::{NonNull, self}, alloc::{self, Layout, alloc, dealloc}, mem, collections::HashMap, cell::{RefCell, Ref, RefMut, BorrowError, BorrowMutError}, ops::DerefMut};
 
-use crate::{world::ArchetypeEntityId, bundle::Bundle, component_info::ComponentInfo, DynTypeId, Tick, Entity};
+use crate::{bundle::Bundle, component_info::ComponentInfo, world::ArchetypeEntityId, DynTypeId, Entities, Entity, Record, Tick};
 
 #[derive(Clone)]
 pub struct ComponentColumn {
@@ -295,21 +295,32 @@ impl Archetype {
             self.capacity = new_cap;
         }
 
-        debug_assert_eq!(self.entity_ids.len(), self.entities.len(), "Somehow the Archetype's entity storage got unsynced");
+        self.ensure_synced();
         let entity_index = ArchetypeEntityId(self.entity_ids.len() as u64);
         self.entity_ids.insert(entity, entity_index);
         self.entities.push(entity);
 
-        bundle.take(|data, type_id, _size| {
+        bundle.take(|data, type_id, info| {
-            let col = self.get_column_mut(type_id).unwrap();
+            self.put_component_at(tick, data, type_id, info.layout().size(), entity_index.0 as _);
-            unsafe { col.insert_entity(entity_index.0 as usize, data, *tick); }
         });
         
         entity_index
     }
 
-    /// Removes an entity from the Archetype and frees its components. Returns the entity record
+    pub(crate) fn put_component_at(&mut self, tick: &Tick, ptr: NonNull<u8>, type_id: DynTypeId, size: usize, index: usize) {
-    /// that took its place in the component column.
+        let _ = size;
+
+        let col = self.get_column_mut(type_id).unwrap();
+        //unsafe { col.set_at(index, ptr, *tick) };
+        unsafe { col.insert_entity(index, ptr, *tick); }
+    }
+
+    /// Removes an entity from the Archetype and frees its components.
+    /// 
+    /// Inside the component columns, the entities are swap-removed. Meaning that the last
+    /// entity in the column is moved in the position of the entity that was removed.
+    /// If there was an entity that was swapped, this function returns the entity, and its
+    /// new index in the archetype that was put in place of the removed entity.
     pub(crate) fn remove_entity(&mut self, entity: Entity, tick: &Tick) -> Option<(Entity, ArchetypeEntityId)> {
         let entity_index = self.entity_ids.remove(&entity)
             .expect("The entity is not in this Archetype!");
@@ -343,7 +354,7 @@ impl Archetype {
         
         let removed = self.entities.swap_remove(entity_index.0 as _);
         assert_eq!(removed, entity);
-        
+
         // now change the ArchetypeEntityId to be the index that the moved entity was moved into.
         removed_entity.map(|(e, _a)| (e, entity_index))
     }
@@ -389,6 +400,11 @@ impl Archetype {
         self.capacity = new_capacity;
     }
 
+    /// Attempts to find the column storing components of `type_id`
+    pub fn get_column_at(&self, idx: usize) -> Option<&ComponentColumn> {
+        self.columns.get(idx)
+    }
+
     /// Attempts to find the column storing components of `type_id`
     pub fn get_column<I: Into<DynTypeId>>(&self, type_id: I) -> Option<&ComponentColumn> {
         let type_id = type_id.into();
@@ -436,7 +452,7 @@ impl Archetype {
     /// The entity IS NOT removed from the old archetype. You must manually call [`Archetype::remove_entity`](crate::Archetype).
     /// It was done this way because I had some borrow check issues when writing [`World::insert`](crate::World)
     /// related to borrowing mutably from self more than once.
-    /* pub fn move_into<B>(&self, into_arch: &mut Archetype, entity: Entity, new_components: B)
+    /* pub fn move_into<B>(&mut self, entities: &mut Entities, tick: &Tick, into_arch: &mut Archetype, entity: Entity, new_components: B)
     where
         B: Bundle
     {
@@ -446,25 +462,40 @@ impl Archetype {
 
         // move the existing components into the new archetype
         for col in self.columns.iter() {
-            let into_col = into_arch.get_column_mut(col.info.type_id).unwrap();
+            let into_col = into_arch.get_column_mut(col.info.type_id()).unwrap();
             
             // copy from the old column into the new column, then remove it from the old one
             unsafe {
                 let ptr = col.borrow_ptr();
                 let ptr = NonNull::new_unchecked(ptr.as_ptr()
-                    .add(new_index.0 as usize * col.info.layout.size));
+                    .add(new_index.0 as usize * col.info.layout().size()));
-                into_col.set_at(new_index.0 as _, ptr);
+                into_col.set_at(new_index.0 as _, ptr, *tick);
+                    //into_col.set_at(new_index.0 as _, ptr);
             }
         }
 
         // now move the new components into the new archetype
         new_components.take(|data, type_id, _size| {
             let col = into_arch.get_column_mut(type_id).unwrap();
-            unsafe { col.set_at(new_index.0 as _, data); }
+            unsafe { col.set_at(new_index.0 as _, data, *tick); }
             col.len += 1;
         });
 
-        //self.remove_entity(entity);
+        if let Some((en, new_idx)) = self.remove_entity(entity, tick) {
+            let moved_rec = Record {
+                id: self.id,
+                index: new_idx,
+            };
+            entities.insert_entity_record(en, moved_rec);
+        }
+        let new_rec = Record {
+            id: into_arch.id,
+            index: new_index,
+        };
+        entities.insert_entity_record(entity, new_rec);
+
+        into_arch.ensure_synced();
+        self.ensure_synced();
     } */
 
     /// Returns a borrow to the map used to find the column indices of the entity.
@@ -700,7 +731,7 @@ mod tests {
     #[test]
     fn dynamic_archetype() {
         let layout = Layout::new::<u32>();
-        let info = ComponentInfo::new_unknown(DynTypeId::Unknown(100), "u32", layout);
+        let info = ComponentInfo::new_unknown(Some("u32".to_string()), DynTypeId::Unknown(100), layout);
         let infos = vec![info.clone()];
 
         let mut a = Archetype::from_bundle_info(super::ArchetypeId(0), infos);

lyra-ecs/src/bundle.rs

@@ -1,4 +1,4 @@
-use std::{ptr::NonNull, mem::size_of, alloc::Layout};
+use std::{ptr::NonNull, alloc::Layout};
 
 use crate::{component::Component, component_info::ComponentInfo, DynTypeId};
 
@@ -11,7 +11,7 @@ pub trait Bundle {
 
     /// Take the bundle by calling the closure with pointers to each component, its type and size.
     /// The closure is expected to take ownership of the pointer.
-    fn take(self, f: impl FnMut(NonNull<u8>, DynTypeId, usize));
+    fn take(self, f: impl FnMut(NonNull<u8>, DynTypeId, ComponentInfo));
 
     /// Returns a boolean indicating if this Bundle is dynamic. See [`DynamicBundle`]
     fn is_dynamic(&self) -> bool;
@@ -26,8 +26,8 @@ impl Bundle for () {
         vec![ComponentInfo::new::<()>()]
     }
 
-    fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, usize)) {
+    fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, ComponentInfo)) {
-        f(NonNull::from(&self).cast(), DynTypeId::of::<()>(), size_of::<()>());
+        f(NonNull::from(&self).cast(), DynTypeId::of::<()>(), ComponentInfo::new::<()>());
     }
 
     fn is_dynamic(&self) -> bool {
@@ -44,8 +44,8 @@ impl<C: Component> Bundle for C {
         vec![ComponentInfo::new::<C>()]
     }
 
-    fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, usize)) {
+    fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, ComponentInfo)) {
-        f(NonNull::from(&self).cast(), DynTypeId::of::<C>(), size_of::<C>());
+        f(NonNull::from(&self).cast(), DynTypeId::of::<C>(), ComponentInfo::new::<C>());
 
         // this must be done to avoid calling drop on heap memory that the component
         // may manage. So something like a Vec, or HashMap, etc.
@@ -70,12 +70,12 @@ macro_rules! impl_bundle_tuple {
                 vec![$(ComponentInfo::new::<$name>()),+]
             }
 
-            fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, usize)) {
+            fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, ComponentInfo)) {
                 // these names wont follow rust convention, but its a macro so deal with it
                 let ($($name,)+) = self;
 
                 $(
-                    f(NonNull::from(&$name).cast(), DynTypeId::of::<$name>(), size_of::<$name>());
+                    f(NonNull::from(&$name).cast(), DynTypeId::of::<$name>(), ComponentInfo::new::<$name>());
                     // this must be done to avoid calling drop on heap memory that the component
                     // may manage. So something like a Vec, or HashMap, etc.
                     std::mem::forget($name);
@@ -136,8 +136,6 @@ impl DynamicBundle {
     where
         C: Component
     {
-        let info = ComponentInfo::new::<C>();
-        
         // an owned pointer must be created from the provided component since comp would drop
         // out of scope and the data would become invalid
         let ptr = unsafe {
@@ -146,17 +144,43 @@ impl DynamicBundle {
             let layout = Layout::new::<C>();
             let alloc_ptr = NonNull::new_unchecked(std::alloc::alloc(layout)).cast::<C>();
             std::ptr::copy_nonoverlapping(data.as_ptr(), alloc_ptr.as_ptr(), 1);
+            
+            // this must be done to avoid calling drop on heap memory that the component
+            // may manage. So something like a Vec, or HashMap, etc.
+            std::mem::forget(comp);
 
             alloc_ptr.cast()
         };
 
+        let info = ComponentInfo::new::<C>();
         self.bundle.push((ptr, info));
     }
 
-    /// Push an unknown type to the bundle
+    /// Push an unknown type to the end of the bundle.
     pub fn push_unknown(&mut self, data: NonNull<u8>, info: ComponentInfo) {
         self.bundle.push((data, info));
     }
+
+    /// Push a bundle to the end of this dynamic bundle.
+    pub fn push_bundle<B>(&mut self, bundle: B)
+    where
+        B: Bundle
+    {
+        bundle.take(|ptr, _, info| {
+            // unfortunately the components in the bundle must be copied since there is no guarantee that
+            // `bundle` lasts for as long as the `DynamicBundle`. If the data wasn't copied, the pointers
+            // could be invalid later.
+            let p = unsafe {
+                let alloc_ptr = NonNull::new_unchecked(std::alloc::alloc(info.layout()));
+                std::ptr::copy_nonoverlapping(ptr.as_ptr(), alloc_ptr.as_ptr(), info.layout().size());
+
+                alloc_ptr
+            };
+
+            self.push_unknown(p, info);
+
+        });
+    }
 }
 
 impl Bundle for DynamicBundle {
@@ -168,9 +192,9 @@ impl Bundle for DynamicBundle {
         self.bundle.iter().map(|b| b.1).collect()
     }
 
-    fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, usize)) {
+    fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, ComponentInfo)) {
-        for (data, info) in self.bundle.iter() {
+        for (data, info) in self.bundle.into_iter() {
-            f(*data, info.type_id(), info.layout().size());
+            f(data, info.type_id(), info);
         }
     }
 

lyra-ecs/src/component_info.rs

@@ -67,7 +67,7 @@ impl ComponentInfo {
     }
 
     /// Create ComponentInfo from a type that is not known to rust
-    pub fn new_unknown<D>(type_id: D, name: &str, layout: Layout) -> Self
+    pub fn new_unknown<D>(name: Option<String>, type_id: D, layout: Layout) -> Self
     where
         D: Into<DynTypeId>,
     {

lyra-ecs/src/entity.rs

@@ -11,6 +11,16 @@ pub struct Entity {
     pub(crate) generation: u64,
 }
 
+impl Entity {
+    pub fn id(&self) -> EntityId {
+        self.id
+    }
+
+    pub fn generation(&self) -> u64 {
+        self.generation
+    }
+}
+
 pub struct Entities {
     pub(crate) arch_index: HashMap<EntityId, Record>,
     dead: VecDeque<Entity>,

lyra-ecs/src/query/dynamic/view.rs

@@ -111,7 +111,7 @@ mod tests {
     #[test]
     fn single_dynamic_view() {
         let comp_layout = Layout::new::<u32>();
-        let comp_info = ComponentInfo::new_unknown(DynTypeId::Unknown(100), "u32", comp_layout);
+        let comp_info = ComponentInfo::new_unknown(Some("u32".to_string()), DynTypeId::Unknown(100), comp_layout);
 
         let mut dynamic_bundle = DynamicBundle::default();
         let comp = 50u32;

lyra-ecs/src/query/filter/mod.rs

@@ -2,4 +2,7 @@ pub mod has_component;
 pub use has_component::*;
 
 pub mod or;
-pub use or::*;
+pub use or::*;
+
+pub mod not;
+pub use not::*;

lyra-ecs/src/query/filter/not.rs

@@ -0,0 +1,45 @@
+use std::marker::PhantomData;
+
+use crate::{query::{AsQuery, Query}, Archetype, World};
+
+#[derive(Default)]
+pub struct Not<Q: Query> {
+    q: Q,
+    _marker: PhantomData<Q>
+}
+
+impl<Q: Query> Copy for Not<Q> {}
+
+impl<Q: Query> Clone for Not<Q> {
+    fn clone(&self) -> Self {
+        Self { 
+            q: self.q.clone(),
+            _marker: self._marker.clone()
+        }
+    }
+}
+
+impl<Q: Query> Query for Not<Q> {
+    type Item<'a> = ();
+    
+    type Fetch<'a> = ();
+
+    fn new() -> Self {
+        Not {
+            q: Q::new(),
+            _marker: PhantomData
+        }
+    }
+
+    fn can_visit_archetype(&self, archetype: &Archetype) -> bool {
+        !self.q.can_visit_archetype(archetype)
+    }
+
+    unsafe fn fetch<'a>(&self, _world: &'a World, _: &'a Archetype, _: crate::Tick) -> Self::Fetch<'a> {
+        ()
+    }
+}
+
+impl<Q: Query> AsQuery for Not<Q> {
+    type Query = Self;
+}

lyra-ecs/src/world.rs

@@ -2,7 +2,7 @@ use std::{any::TypeId, collections::HashMap, ptr::NonNull};
 
 use atomic_refcell::{AtomicRef, AtomicRefMut};
 
-use crate::{archetype::{Archetype, ArchetypeId}, bundle::Bundle, query::{dynamic::DynamicView, AsQuery, Query, ViewState, ViewIter, ViewOne}, resource::ResourceData, ComponentInfo, DynTypeId, Entities, Entity, ResourceObject, Tick, TickTracker};
+use crate::{archetype::{Archetype, ArchetypeId}, bundle::Bundle, query::{dynamic::DynamicView, AsQuery, Query, ViewIter, ViewOne, ViewState}, resource::ResourceData, ComponentInfo, DynTypeId, DynamicBundle, Entities, Entity, ResourceObject, Tick, TickTracker};
 
 /// The id of the entity for the Archetype.
 /// 
@@ -144,37 +144,32 @@ impl World {
         let current_arch = self.archetypes.get(&record.id).unwrap();
         let current_arch_len = current_arch.len();
 
-        let mut col_types: Vec<DynTypeId> = current_arch.columns.iter().map(|c| c.info.type_id()).collect();
+        // contains the type ids for the old component columns + the ids for the new components
-        let orig_col = col_types.clone();
+        let mut combined_column_types: Vec<DynTypeId> = current_arch.columns.iter().map(|c| c.info.type_id()).collect();
-        col_types.extend(bundle.type_ids());
+        combined_column_types.extend(bundle.type_ids());
         
-        let mut col_infos: Vec<ComponentInfo> = current_arch.columns.iter().map(|c| c.info).collect();
+        // contains the ComponentInfo for the old component columns + the info for the new components
-        col_infos.extend(bundle.info());
+        let mut combined_column_infos: Vec<ComponentInfo> = current_arch.columns.iter().map(|c| c.info).collect();
+        combined_column_infos.extend(bundle.info());
 
-        let col_ptrs: Vec<(NonNull<u8>, ComponentInfo)> = current_arch.columns.iter()
+        // pointers only for the old columns
+        let old_columns: Vec<(NonNull<u8>, ComponentInfo)> = current_arch.columns.iter()
             .map(|c| unsafe { (NonNull::new_unchecked(c.borrow_ptr().as_ptr()), c.info) })
             .collect();
 
-        if let Some(arch) = self.archetypes.values_mut().find(|a| a.is_archetype_for(&col_types)) {
+        if let Some(arch) = self.archetypes.values_mut().find(|a| a.is_archetype_for(&combined_column_types)) {
-            let res_index = arch.reserve_one(entity);
+            let mut dbun = DynamicBundle::new();
-
+            // move old entity components into new archetype columns
-            for (col_type, (col_ptr, col_info)) in orig_col.into_iter().zip(col_ptrs.into_iter()) {
+            for (col_ptr, col_info) in old_columns.into_iter() {
                 unsafe {
                     let ptr = NonNull::new_unchecked(col_ptr.as_ptr()
                         .add(record.index.0 as usize * col_info.layout().size()));
-                    let col = arch.get_column_mut(col_type).unwrap();
+                    dbun.push_unknown(ptr, col_info);
-                    // set_at is used since the entity was reserved
-                    col.set_at(res_index.0 as _, ptr, tick);
                 }
             }
+            dbun.push_bundle(bundle);
 
-            bundle.take(|data, type_id, _size| {
+            let res_index = arch.add_entity(entity, dbun, &tick);
-                let col = arch.get_column_mut(type_id).unwrap();
-                // set_at is used since the entity was reserved
-                unsafe { col.set_at(res_index.0 as _, data, tick); }
-            });
-
-            arch.entity_ids.insert(entity, res_index);
             arch.ensure_synced();
             
             let new_record = Record {
@@ -187,25 +182,24 @@ impl World {
                 // if this entity is the only entity for this archetype, add more columns to it
                 let current_arch = self.archetypes.get_mut(&record.id).unwrap();
                 current_arch.extend(&tick, vec![bundle]);
-
                 return;
             }
 
             let new_arch_id = self.next_archetype_id.increment();
-            let mut archetype = Archetype::from_bundle_info(new_arch_id, col_infos);
+            let mut archetype = Archetype::from_bundle_info(new_arch_id, combined_column_infos);
-            let entity_arch_id = archetype.add_entity(entity, bundle, &tick);
             
-            // move the old components into the new archetype
+            let mut dbun = DynamicBundle::new();
-            for (column_ptr, column_info) in col_ptrs.into_iter() {
+            for (column_ptr, column_info) in old_columns.into_iter() {
                 unsafe {
                     // ptr of component for the entity
                     let comp_ptr = NonNull::new_unchecked(column_ptr.as_ptr()
                         .add(record.index.0 as usize * column_info.layout().size()));
-                    
+                    dbun.push_unknown(comp_ptr, column_info);
-                    let col = archetype.get_column_mut(column_info.type_id()).unwrap();
-                    col.insert_entity(entity_arch_id.0 as _, comp_ptr, tick);
                 }
             }
+            dbun.push_bundle(bundle);
+
+            let entity_arch_id = archetype.add_entity(entity, dbun, &tick);
 
             self.archetypes.insert(new_arch_id, archetype);
 
@@ -219,12 +213,103 @@ impl World {
         }
 
         let current_arch = self.archetypes.get_mut(&record.id).unwrap();
-        if current_arch.len() > 1 {
+        if let Some((en, enar)) = current_arch.remove_entity(entity, &tick) {
-            current_arch.remove_entity(entity, &tick);
+            let rec = Record {
-        } else if current_arch.len() == 1 {
+                id: current_arch.id(),
-            // The old archetype will only be removed if there was another archetype that would
+                index: enar
-            // work for the entity's components, and the old archetype only had a single entity.
+            };
-            self.archetypes.remove(&record.id).unwrap();
+            self.entities.insert_entity_record(en, rec);
+        }   
+
+        current_arch.ensure_synced();
+    }
+
+    /// A method used for debugging implementation details of the ECS.
+    /// 
+    /// Here's an example of the output:
+    /// ```
+    /// Entities
+    ///   1 in archetype 0 at 0
+    ///   0 in archetype 1 at 0
+    ///   2 in archetype 0 at 1
+    ///   3 in archetype 2 at 0
+    /// Arch 1 -- 1 entities
+    ///   Col 175564825027445222460146453544114453753
+    ///     0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 63 0 0 128 63 0 0 128 63 0 0 128 63 78 86 0 0
+    ///   Col 162279302565774655543278578489329315472
+    ///     0: 0 0 32 65 0 0 32 65 0 0 32 65 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 63 0 0 128 63 0 0 128 63 0 0 128 63 0 0 0 0
+    ///   Col 24291284537013640759061027938209843602
+    ///     0: 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+    /// Arch 2 -- 1 entities
+    ///   Col 175564825027445222460146453544114453753
+    ///     0: 0 0 0 0 0 0 0 0 0 0 0 0 237 127 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 63 0 0 128 63 0 0 128 63 0 0 128 63 78 86 0 0
+    ///   Col 162279302565774655543278578489329315472
+    ///     0: 0 0 76 66 0 0 170 66 0 0 136 65 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 63 0 0 128 63 0 0 128 63 0 0 128 63 0 0 0 0
+    ///   Col 142862377085187052737282554588643015580
+    ///     0: 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+    /// Arch 0 -- 2 entities
+    ///   Col 175564825027445222460146453544114453753
+    ///     0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 32 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 63 0 0 128 63 0 0 128 63 0 0 128 63 0 0 0 0
+    ///     1: 0 0 0 0 0 0 0 0 0 0 0 0 237 127 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 63 0 0 128 63 0 0 128 63 0 0 128 63 78 86 0 0
+    ///   Col 162279302565774655543278578489329315472
+    ///     0: 0 0 112 65 0 0 112 65 0 0 112 65 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 63 0 0 128 63 0 0 128 63 0 0 128 63 0 0 0 0
+    ///     1: 0 0 27 67 0 0 184 65 0 0 192 64 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 63 0 0 128 63 0 0 128 63 0 0 128 63 0 0 0 0
+    ///   Col 142862377085187052737282554588643015580
+    ///     0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+    ///     1: 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+    ///   Col 24291284537013640759061027938209843602
+    ///     0: 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+    ///     1: 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+    /// Arch 3 -- 0 entities
+    ///   Col 175564825027445222460146453544114453753
+    ///   Col 162279302565774655543278578489329315472
+    /// ```
+    /// 
+    /// This output prints all Entity ids, the archetype they're in, and the index that they're
+    /// in inside of the archetype. Additionally, the archetypes are printing, including their
+    /// columns type ids, and the contents of the type ids. This output can be used to debug
+    /// the contents of entities inside the archetypes.
+    /// 
+    /// Below is a template of the output:
+    /// ```
+    /// Entities
+    ///   %ENTITY_ID% in archetype %ARCHETYPE_ID% at %INDEX%
+    /// Arch ID -- %ARCHETYPE_LEN% entities
+    ///   %FOR EACH COL%
+    ///   Col COLUMN_COMPONENT_TYPE_ID
+    ///     %FOR EACH ENTITY%
+    ///     %ENTITY_INDEX%: %COMPONENT_BYTES%
+    /// ```
+    /// If the template above doesn't help you in understanding the output, read the source code
+    /// of the function. The source code is pretty simple.
+    pub fn debug_print_world(&self) {
+        println!("Entities");
+        for (en, rec) in &self.entities.arch_index {
+            println!("  {} in archetype {} at {}", en.0, rec.id.0, rec.index.0);
+        }
+
+        for arch in self.archetypes.values() {
+            println!("Arch {} -- {} entities", arch.id().0, arch.len());
+
+            for col in &arch.columns {
+                // no clue if doing this is stable, but this is a debug function so :shrug:
+                let tyid: u128 = unsafe { std::mem::transmute(col.info.type_id().as_rust()) };
+                println!("  Col {}", tyid);
+
+                for en in 0..col.len {
+                    // get the ptr starting at the component
+                    let p = col.borrow_ptr();
+                    let p = unsafe { p.as_ptr().add(en * col.info.layout().size()) };
+
+                    print!("    {}: ", en);
+                    // print each byte of the component
+                    for i in 0..col.info.layout().size() {
+                        let d = unsafe { *p.add(i) };
+                        print!("{} ", d);
+                    }
+                    println!();
+                }
+            }
         }
     }
 
@@ -364,6 +449,10 @@ impl World {
         self.resources.get(&TypeId::of::<T>())
             .map(|d| unsafe { NonNull::new_unchecked(d.data.as_ptr() as *mut T) })
     }
+
+    pub fn archetype_count(&self) -> usize {
+        self.archetypes.len()
+    }
 }
 
 // TODO: Ensure that all non-send resources are only accessible on the main thread.