[Merged by Bors] - Directly copy moved Table components to the target location

crates/bevy_ecs/src/query/mod.rs

@@ -11,7 +11,7 @@ pub use iter::*;
 pub use state::*;
 
 #[allow(unreachable_code)]
-unsafe fn debug_checked_unreachable() -> ! {
+pub(crate) unsafe fn debug_checked_unreachable() -> ! {
     #[cfg(debug_assertions)]
     unreachable!();
     std::hint::unreachable_unchecked();

crates/bevy_ecs/src/storage/blob_vec.rs

@@ -209,6 +209,29 @@ impl BlobVec {
         OwningPtr::new(self.swap_scratch)
     }
 
+    /// Removes the value at `index` and copies the value stored into `ptr`.
+    /// Does not do any bounds checking on `index`.
+    ///
+    /// # Safety
+    /// It is the caller's responsibility to ensure that `index` is < `self.len()`
+    /// and that `self[index]` has been properly initialized.
+    #[inline]
+    pub unsafe fn remove_unchecked(&mut self, index: usize, ptr: PtrMut<'_>) {
+        debug_assert!(index < self.len());
+        let last = self.len - 1;
+        std::ptr::copy_nonoverlapping::<u8>(
+            self.get_unchecked_mut(index).as_ptr(),
+            ptr.as_ptr(),
+            self.item_layout.size(),
+        );
+        std::ptr::copy::<u8>(
+            self.get_unchecked_mut(last).as_ptr(),
+            self.get_unchecked_mut(index).as_ptr(),
+            self.item_layout.size(),
+        );
+        self.len -= 1;
+    }
+
     /// # Safety
     /// It is the caller's responsibility to ensure that `index` is < self.len()
     #[inline]

crates/bevy_ecs/src/storage/table.rs

@@ -1,6 +1,7 @@
 use crate::{
     component::{ComponentId, ComponentInfo, ComponentTicks, Components},
     entity::Entity,
+    query::debug_checked_unreachable,
     storage::{BlobVec, SparseSet},
 };
 use bevy_ptr::{OwningPtr, Ptr, PtrMut};
@@ -119,6 +120,30 @@ impl Column {
         (data, ticks)
     }
 
+    /// Removes the element from `other` at `src_row` and inserts it
+    /// into the current column to initialize the values at `dst_row`.
+    /// Does not do any bounds checking.
+    ///
+    /// # Safety
+    ///
+    ///  - `other` must have the same data layout as `self`
+    ///  - `src_row` must be in bounds for `other`
+    ///  - `dst_row` must be in bounds for `self`
+    ///  - `other[src_row]` must be initialized to a valid value.
+    ///  - `self[dst_row]` must not be initalized yet.
+    #[inline]
+    pub(crate) unsafe fn initialize_from_unchecked(
+        &mut self,
+        other: &mut Column,
+        src_row: usize,
+        dst_row: usize,
+    ) {
+        debug_assert!(self.data.layout() == other.data.layout());
+        let ptr = self.data.get_unchecked_mut(dst_row);
+        other.data.remove_unchecked(src_row, ptr);
+        *self.ticks.get_unchecked_mut(dst_row) = other.ticks.swap_remove(src_row);
+    }
+
     // # Safety
     // - ptr must point to valid data of this column's component type
     pub(crate) unsafe fn push(&mut self, ptr: OwningPtr<'_>, ticks: ComponentTicks) {
@@ -253,9 +278,11 @@ impl Table {
         let is_last = row == self.entities.len() - 1;
         let new_row = new_table.allocate(self.entities.swap_remove(row));
         for (component_id, column) in self.columns.iter_mut() {
-            let (data, ticks) = column.swap_remove_and_forget_unchecked(row);
             if let Some(new_column) = new_table.get_column_mut(*component_id) {
-                new_column.initialize(new_row, data, ticks);
+                new_column.initialize_from_unchecked(column, row, new_row);
+            } else {
+                // It's the caller's responsibility to drop these cases.
+                let (_, _) = column.swap_remove_and_forget_unchecked(row);
             }
         }
         TableMoveResult {
@@ -284,8 +311,7 @@ impl Table {
         let new_row = new_table.allocate(self.entities.swap_remove(row));
         for (component_id, column) in self.columns.iter_mut() {
             if let Some(new_column) = new_table.get_column_mut(*component_id) {
-                let (data, ticks) = column.swap_remove_and_forget_unchecked(row);
-                new_column.initialize(new_row, data, ticks);
+                new_column.initialize_from_unchecked(column, row, new_row);
             } else {
                 column.swap_remove_unchecked(row);
             }
@@ -315,9 +341,10 @@ impl Table {
         let is_last = row == self.entities.len() - 1;
         let new_row = new_table.allocate(self.entities.swap_remove(row));
         for (component_id, column) in self.columns.iter_mut() {
-            let new_column = new_table.get_column_mut(*component_id).unwrap();
-            let (data, ticks) = column.swap_remove_and_forget_unchecked(row);
-            new_column.initialize(new_row, data, ticks);
+            new_table
+                .get_column_mut(*component_id)
+                .unwrap_or_else(|| debug_checked_unreachable())
+                .initialize_from_unchecked(column, row, new_row);
         }
         TableMoveResult {
             new_row,