ids: Add IdSetSeq

This is an often more efficient replacement for a `IdVec<I, HashSet<T>>`
implemented on top of a `SetSeq<T>`.

ids/Cargo.toml

@@ -12,6 +12,7 @@ workspace = true
 hashbrown = { version = "0.14.5", default-features = false, features = ["inline-more"] }
 imctk-derive = { path = "../derive" }
 imctk-transparent = { path = "../transparent" }
+table_seq = { path = "../table_seq" }
 zwohash = "0.1.2"
 
 [dev-dependencies]

ids/src/id_set_seq.rs

@@ -0,0 +1,94 @@
+//! Id indexed sequence of hash sets.
+use std::{hash::BuildHasherDefault, marker::PhantomData};
+
+use table_seq::set_seq::{SetSeq, SetSeqSet, SetSeqSetMut};
+use zwohash::ZwoHasher;
+
+use crate::Id;
+
+/// Indexed sequence of hash sets.
+///
+/// This type serves as a memory and runtime efficient replacement for `IdVec<I, HashSet<T>>`.
+pub struct IdSetSeq<I: Id, T, S = BuildHasherDefault<ZwoHasher>> {
+    set_seq: SetSeq<T, S>,
+    _phantom: PhantomData<I>,
+}
+
+impl<I: Id, T, S> std::ops::Deref for IdSetSeq<I, T, S> {
+    type Target = SetSeq<T, S>;
+
+    #[inline(always)]
+    fn deref(&self) -> &Self::Target {
+        &self.set_seq
+    }
+}
+
+impl<I: Id, T, S> IdSetSeq<I, T, S> {
+    /// Discards all sets in the sequence.
+    #[inline(always)]
+    pub fn clear(&mut self) {
+        self.set_seq.clear();
+    }
+
+    /// Resizes the sequence by appending empty sets or discarding trailing sets.
+    #[inline(always)]
+    pub fn resize(&mut self, len: usize) {
+        self.set_seq.resize(len);
+    }
+
+    /// Ensures that the sequence contains a set for the given id by appending emtpy sets if the
+    /// sequence was too short.
+    ///
+    /// Provides mutable access to the set for the given id.
+    #[inline(always)]
+    pub fn grow_for(&mut self, id: I) -> SetSeqSetMut<T, S> {
+        self.set_seq.grow_for(id.id_index())
+    }
+
+    /// Provides shared access to the set for a given id, panics if the id is out-of-bounds.
+    ///
+    /// This is used instead of [`std::ops::Index`], as it returns a value of the custom
+    /// reference-like [`SetSeqSet`] type.
+    ///
+    /// Panics if `id.id_index() >= self.len()`.
+    #[inline(always)]
+    pub fn at(&self, id: I) -> SetSeqSet<T, S> {
+        self.set_seq.at(id.id_index())
+    }
+
+    /// Provides mutable access to the set for a given id, panics if the id is out-of-bounds.
+    ///
+    /// This is used instead of [`std::ops::IndexMut`], as it returns a value of the custom
+    /// reference-like [`SetSeqSetMut`] type.
+    ///
+    /// Panics if `id.id_index() >= self.len()`.
+    #[inline(always)]
+    pub fn at_mut(&mut self, id: I) -> SetSeqSetMut<T, S> {
+        self.set_seq.at_mut(id.id_index())
+    }
+
+    /// Provides shared access to the set for a given id.
+    ///
+    /// This returns `None` if `id.id_index() >= self.len()`.
+    #[inline(always)]
+    pub fn get(&self, id: I) -> Option<SetSeqSet<T, S>> {
+        self.set_seq.get(id.id_index())
+    }
+
+    /// Provides mutable access to the set for a given id.
+    ///
+    /// This returns `None` if `id.id_index() >= self.len()`.
+    #[inline(always)]
+    pub fn get_mut(&mut self, id: I) -> Option<SetSeqSetMut<T, S>> {
+        self.set_seq.get_mut(id.id_index())
+    }
+}
+
+impl<I: Id, T, S: Default> Default for IdSetSeq<I, T, S> {
+    fn default() -> Self {
+        Self {
+            set_seq: Default::default(),
+            _phantom: PhantomData,
+        }
+    }
+}

ids/src/lib.rs

@@ -17,6 +17,8 @@ mod id_range;
 pub mod id_vec;
 pub mod indexed_id_vec;
 
+pub mod id_set_seq;
+
 /// Derives an [`Id`] instance for a newtype wrapper around an existing [`Id`] type.
 ///
 /// Deriving an [`Id`] instance requires the `#[repr(transparent)]` attribute on the target struct.