diff options
Diffstat (limited to 'library/alloc/src/collections/btree/navigate.rs')
-rw-r--r-- | library/alloc/src/collections/btree/navigate.rs | 719 |
1 files changed, 719 insertions, 0 deletions
diff --git a/library/alloc/src/collections/btree/navigate.rs b/library/alloc/src/collections/btree/navigate.rs new file mode 100644 index 000000000..1e33c1e64 --- /dev/null +++ b/library/alloc/src/collections/btree/navigate.rs @@ -0,0 +1,719 @@ +use core::borrow::Borrow; +use core::hint; +use core::ops::RangeBounds; +use core::ptr; + +use super::node::{marker, ForceResult::*, Handle, NodeRef}; + +use crate::alloc::Allocator; +// `front` and `back` are always both `None` or both `Some`. +pub struct LeafRange<BorrowType, K, V> { + front: Option<Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>>, + back: Option<Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>>, +} + +impl<'a, K: 'a, V: 'a> Clone for LeafRange<marker::Immut<'a>, K, V> { + fn clone(&self) -> Self { + LeafRange { front: self.front.clone(), back: self.back.clone() } + } +} + +impl<BorrowType, K, V> LeafRange<BorrowType, K, V> { + pub fn none() -> Self { + LeafRange { front: None, back: None } + } + + fn is_empty(&self) -> bool { + self.front == self.back + } + + /// Temporarily takes out another, immutable equivalent of the same range. + pub fn reborrow(&self) -> LeafRange<marker::Immut<'_>, K, V> { + LeafRange { + front: self.front.as_ref().map(|f| f.reborrow()), + back: self.back.as_ref().map(|b| b.reborrow()), + } + } +} + +impl<'a, K, V> LeafRange<marker::Immut<'a>, K, V> { + #[inline] + pub fn next_checked(&mut self) -> Option<(&'a K, &'a V)> { + self.perform_next_checked(|kv| kv.into_kv()) + } + + #[inline] + pub fn next_back_checked(&mut self) -> Option<(&'a K, &'a V)> { + self.perform_next_back_checked(|kv| kv.into_kv()) + } +} + +impl<'a, K, V> LeafRange<marker::ValMut<'a>, K, V> { + #[inline] + pub fn next_checked(&mut self) -> Option<(&'a K, &'a mut V)> { + self.perform_next_checked(|kv| unsafe { ptr::read(kv) }.into_kv_valmut()) + } + + #[inline] + pub fn next_back_checked(&mut self) -> Option<(&'a K, &'a mut V)> { + self.perform_next_back_checked(|kv| unsafe { ptr::read(kv) }.into_kv_valmut()) + } +} + +impl<BorrowType: marker::BorrowType, K, V> LeafRange<BorrowType, K, V> { + /// If possible, extract some result from the following KV and move to the edge beyond it. + fn perform_next_checked<F, R>(&mut self, f: F) -> Option<R> + where + F: Fn(&Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV>) -> R, + { + if self.is_empty() { + None + } else { + super::mem::replace(self.front.as_mut().unwrap(), |front| { + let kv = front.next_kv().ok().unwrap(); + let result = f(&kv); + (kv.next_leaf_edge(), Some(result)) + }) + } + } + + /// If possible, extract some result from the preceding KV and move to the edge beyond it. + fn perform_next_back_checked<F, R>(&mut self, f: F) -> Option<R> + where + F: Fn(&Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV>) -> R, + { + if self.is_empty() { + None + } else { + super::mem::replace(self.back.as_mut().unwrap(), |back| { + let kv = back.next_back_kv().ok().unwrap(); + let result = f(&kv); + (kv.next_back_leaf_edge(), Some(result)) + }) + } + } +} + +enum LazyLeafHandle<BorrowType, K, V> { + Root(NodeRef<BorrowType, K, V, marker::LeafOrInternal>), // not yet descended + Edge(Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>), +} + +impl<'a, K: 'a, V: 'a> Clone for LazyLeafHandle<marker::Immut<'a>, K, V> { + fn clone(&self) -> Self { + match self { + LazyLeafHandle::Root(root) => LazyLeafHandle::Root(*root), + LazyLeafHandle::Edge(edge) => LazyLeafHandle::Edge(*edge), + } + } +} + +impl<BorrowType, K, V> LazyLeafHandle<BorrowType, K, V> { + fn reborrow(&self) -> LazyLeafHandle<marker::Immut<'_>, K, V> { + match self { + LazyLeafHandle::Root(root) => LazyLeafHandle::Root(root.reborrow()), + LazyLeafHandle::Edge(edge) => LazyLeafHandle::Edge(edge.reborrow()), + } + } +} + +// `front` and `back` are always both `None` or both `Some`. +pub struct LazyLeafRange<BorrowType, K, V> { + front: Option<LazyLeafHandle<BorrowType, K, V>>, + back: Option<LazyLeafHandle<BorrowType, K, V>>, +} + +impl<'a, K: 'a, V: 'a> Clone for LazyLeafRange<marker::Immut<'a>, K, V> { + fn clone(&self) -> Self { + LazyLeafRange { front: self.front.clone(), back: self.back.clone() } + } +} + +impl<BorrowType, K, V> LazyLeafRange<BorrowType, K, V> { + pub fn none() -> Self { + LazyLeafRange { front: None, back: None } + } + + /// Temporarily takes out another, immutable equivalent of the same range. + pub fn reborrow(&self) -> LazyLeafRange<marker::Immut<'_>, K, V> { + LazyLeafRange { + front: self.front.as_ref().map(|f| f.reborrow()), + back: self.back.as_ref().map(|b| b.reborrow()), + } + } +} + +impl<'a, K, V> LazyLeafRange<marker::Immut<'a>, K, V> { + #[inline] + pub unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) { + unsafe { self.init_front().unwrap().next_unchecked() } + } + + #[inline] + pub unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) { + unsafe { self.init_back().unwrap().next_back_unchecked() } + } +} + +impl<'a, K, V> LazyLeafRange<marker::ValMut<'a>, K, V> { + #[inline] + pub unsafe fn next_unchecked(&mut self) -> (&'a K, &'a mut V) { + unsafe { self.init_front().unwrap().next_unchecked() } + } + + #[inline] + pub unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) { + unsafe { self.init_back().unwrap().next_back_unchecked() } + } +} + +impl<K, V> LazyLeafRange<marker::Dying, K, V> { + fn take_front( + &mut self, + ) -> Option<Handle<NodeRef<marker::Dying, K, V, marker::Leaf>, marker::Edge>> { + match self.front.take()? { + LazyLeafHandle::Root(root) => Some(root.first_leaf_edge()), + LazyLeafHandle::Edge(edge) => Some(edge), + } + } + + #[inline] + pub unsafe fn deallocating_next_unchecked<A: Allocator + Clone>( + &mut self, + alloc: A, + ) -> Handle<NodeRef<marker::Dying, K, V, marker::LeafOrInternal>, marker::KV> { + debug_assert!(self.front.is_some()); + let front = self.init_front().unwrap(); + unsafe { front.deallocating_next_unchecked(alloc) } + } + + #[inline] + pub unsafe fn deallocating_next_back_unchecked<A: Allocator + Clone>( + &mut self, + alloc: A, + ) -> Handle<NodeRef<marker::Dying, K, V, marker::LeafOrInternal>, marker::KV> { + debug_assert!(self.back.is_some()); + let back = self.init_back().unwrap(); + unsafe { back.deallocating_next_back_unchecked(alloc) } + } + + #[inline] + pub fn deallocating_end<A: Allocator + Clone>(&mut self, alloc: A) { + if let Some(front) = self.take_front() { + front.deallocating_end(alloc) + } + } +} + +impl<BorrowType: marker::BorrowType, K, V> LazyLeafRange<BorrowType, K, V> { + fn init_front( + &mut self, + ) -> Option<&mut Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>> { + if let Some(LazyLeafHandle::Root(root)) = &self.front { + self.front = Some(LazyLeafHandle::Edge(unsafe { ptr::read(root) }.first_leaf_edge())); + } + match &mut self.front { + None => None, + Some(LazyLeafHandle::Edge(edge)) => Some(edge), + // SAFETY: the code above would have replaced it. + Some(LazyLeafHandle::Root(_)) => unsafe { hint::unreachable_unchecked() }, + } + } + + fn init_back( + &mut self, + ) -> Option<&mut Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>> { + if let Some(LazyLeafHandle::Root(root)) = &self.back { + self.back = Some(LazyLeafHandle::Edge(unsafe { ptr::read(root) }.last_leaf_edge())); + } + match &mut self.back { + None => None, + Some(LazyLeafHandle::Edge(edge)) => Some(edge), + // SAFETY: the code above would have replaced it. + Some(LazyLeafHandle::Root(_)) => unsafe { hint::unreachable_unchecked() }, + } + } +} + +impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::LeafOrInternal> { + /// Finds the distinct leaf edges delimiting a specified range in a tree. + /// + /// If such distinct edges exist, returns them in ascending order, meaning + /// that a non-zero number of calls to `next_unchecked` on the `front` of + /// the result and/or calls to `next_back_unchecked` on the `back` of the + /// result will eventually reach the same edge. + /// + /// If there are no such edges, i.e., if the tree contains no key within + /// the range, returns an empty `front` and `back`. + /// + /// # Safety + /// Unless `BorrowType` is `Immut`, do not use the handles to visit the same + /// KV twice. + unsafe fn find_leaf_edges_spanning_range<Q: ?Sized, R>( + self, + range: R, + ) -> LeafRange<BorrowType, K, V> + where + Q: Ord, + K: Borrow<Q>, + R: RangeBounds<Q>, + { + match self.search_tree_for_bifurcation(&range) { + Err(_) => LeafRange::none(), + Ok(( + node, + lower_edge_idx, + upper_edge_idx, + mut lower_child_bound, + mut upper_child_bound, + )) => { + let mut lower_edge = unsafe { Handle::new_edge(ptr::read(&node), lower_edge_idx) }; + let mut upper_edge = unsafe { Handle::new_edge(node, upper_edge_idx) }; + loop { + match (lower_edge.force(), upper_edge.force()) { + (Leaf(f), Leaf(b)) => return LeafRange { front: Some(f), back: Some(b) }, + (Internal(f), Internal(b)) => { + (lower_edge, lower_child_bound) = + f.descend().find_lower_bound_edge(lower_child_bound); + (upper_edge, upper_child_bound) = + b.descend().find_upper_bound_edge(upper_child_bound); + } + _ => unreachable!("BTreeMap has different depths"), + } + } + } + } + } +} + +fn full_range<BorrowType: marker::BorrowType, K, V>( + root1: NodeRef<BorrowType, K, V, marker::LeafOrInternal>, + root2: NodeRef<BorrowType, K, V, marker::LeafOrInternal>, +) -> LazyLeafRange<BorrowType, K, V> { + LazyLeafRange { + front: Some(LazyLeafHandle::Root(root1)), + back: Some(LazyLeafHandle::Root(root2)), + } +} + +impl<'a, K: 'a, V: 'a> NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal> { + /// Finds the pair of leaf edges delimiting a specific range in a tree. + /// + /// The result is meaningful only if the tree is ordered by key, like the tree + /// in a `BTreeMap` is. + pub fn range_search<Q, R>(self, range: R) -> LeafRange<marker::Immut<'a>, K, V> + where + Q: ?Sized + Ord, + K: Borrow<Q>, + R: RangeBounds<Q>, + { + // SAFETY: our borrow type is immutable. + unsafe { self.find_leaf_edges_spanning_range(range) } + } + + /// Finds the pair of leaf edges delimiting an entire tree. + pub fn full_range(self) -> LazyLeafRange<marker::Immut<'a>, K, V> { + full_range(self, self) + } +} + +impl<'a, K: 'a, V: 'a> NodeRef<marker::ValMut<'a>, K, V, marker::LeafOrInternal> { + /// Splits a unique reference into a pair of leaf edges delimiting a specified range. + /// The result are non-unique references allowing (some) mutation, which must be used + /// carefully. + /// + /// The result is meaningful only if the tree is ordered by key, like the tree + /// in a `BTreeMap` is. + /// + /// # Safety + /// Do not use the duplicate handles to visit the same KV twice. + pub fn range_search<Q, R>(self, range: R) -> LeafRange<marker::ValMut<'a>, K, V> + where + Q: ?Sized + Ord, + K: Borrow<Q>, + R: RangeBounds<Q>, + { + unsafe { self.find_leaf_edges_spanning_range(range) } + } + + /// Splits a unique reference into a pair of leaf edges delimiting the full range of the tree. + /// The results are non-unique references allowing mutation (of values only), so must be used + /// with care. + pub fn full_range(self) -> LazyLeafRange<marker::ValMut<'a>, K, V> { + // We duplicate the root NodeRef here -- we will never visit the same KV + // twice, and never end up with overlapping value references. + let self2 = unsafe { ptr::read(&self) }; + full_range(self, self2) + } +} + +impl<K, V> NodeRef<marker::Dying, K, V, marker::LeafOrInternal> { + /// Splits a unique reference into a pair of leaf edges delimiting the full range of the tree. + /// The results are non-unique references allowing massively destructive mutation, so must be + /// used with the utmost care. + pub fn full_range(self) -> LazyLeafRange<marker::Dying, K, V> { + // We duplicate the root NodeRef here -- we will never access it in a way + // that overlaps references obtained from the root. + let self2 = unsafe { ptr::read(&self) }; + full_range(self, self2) + } +} + +impl<BorrowType: marker::BorrowType, K, V> + Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> +{ + /// Given a leaf edge handle, returns [`Result::Ok`] with a handle to the neighboring KV + /// on the right side, which is either in the same leaf node or in an ancestor node. + /// If the leaf edge is the last one in the tree, returns [`Result::Err`] with the root node. + pub fn next_kv( + self, + ) -> Result< + Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV>, + NodeRef<BorrowType, K, V, marker::LeafOrInternal>, + > { + let mut edge = self.forget_node_type(); + loop { + edge = match edge.right_kv() { + Ok(kv) => return Ok(kv), + Err(last_edge) => match last_edge.into_node().ascend() { + Ok(parent_edge) => parent_edge.forget_node_type(), + Err(root) => return Err(root), + }, + } + } + } + + /// Given a leaf edge handle, returns [`Result::Ok`] with a handle to the neighboring KV + /// on the left side, which is either in the same leaf node or in an ancestor node. + /// If the leaf edge is the first one in the tree, returns [`Result::Err`] with the root node. + fn next_back_kv( + self, + ) -> Result< + Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV>, + NodeRef<BorrowType, K, V, marker::LeafOrInternal>, + > { + let mut edge = self.forget_node_type(); + loop { + edge = match edge.left_kv() { + Ok(kv) => return Ok(kv), + Err(last_edge) => match last_edge.into_node().ascend() { + Ok(parent_edge) => parent_edge.forget_node_type(), + Err(root) => return Err(root), + }, + } + } + } +} + +impl<BorrowType: marker::BorrowType, K, V> + Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge> +{ + /// Given an internal edge handle, returns [`Result::Ok`] with a handle to the neighboring KV + /// on the right side, which is either in the same internal node or in an ancestor node. + /// If the internal edge is the last one in the tree, returns [`Result::Err`] with the root node. + fn next_kv( + self, + ) -> Result< + Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::KV>, + NodeRef<BorrowType, K, V, marker::Internal>, + > { + let mut edge = self; + loop { + edge = match edge.right_kv() { + Ok(internal_kv) => return Ok(internal_kv), + Err(last_edge) => match last_edge.into_node().ascend() { + Ok(parent_edge) => parent_edge, + Err(root) => return Err(root), + }, + } + } + } +} + +impl<K, V> Handle<NodeRef<marker::Dying, K, V, marker::Leaf>, marker::Edge> { + /// Given a leaf edge handle into a dying tree, returns the next leaf edge + /// on the right side, and the key-value pair in between, if they exist. + /// + /// If the given edge is the last one in a leaf, this method deallocates + /// the leaf, as well as any ancestor nodes whose last edge was reached. + /// This implies that if no more key-value pair follows, the entire tree + /// will have been deallocated and there is nothing left to return. + /// + /// # Safety + /// - The given edge must not have been previously returned by counterpart + /// `deallocating_next_back`. + /// - The returned KV handle is only valid to access the key and value, + /// and only valid until the next call to a `deallocating_` method. + unsafe fn deallocating_next<A: Allocator + Clone>( + self, + alloc: A, + ) -> Option<(Self, Handle<NodeRef<marker::Dying, K, V, marker::LeafOrInternal>, marker::KV>)> + { + let mut edge = self.forget_node_type(); + loop { + edge = match edge.right_kv() { + Ok(kv) => return Some((unsafe { ptr::read(&kv) }.next_leaf_edge(), kv)), + Err(last_edge) => { + match unsafe { last_edge.into_node().deallocate_and_ascend(alloc.clone()) } { + Some(parent_edge) => parent_edge.forget_node_type(), + None => return None, + } + } + } + } + } + + /// Given a leaf edge handle into a dying tree, returns the next leaf edge + /// on the left side, and the key-value pair in between, if they exist. + /// + /// If the given edge is the first one in a leaf, this method deallocates + /// the leaf, as well as any ancestor nodes whose first edge was reached. + /// This implies that if no more key-value pair follows, the entire tree + /// will have been deallocated and there is nothing left to return. + /// + /// # Safety + /// - The given edge must not have been previously returned by counterpart + /// `deallocating_next`. + /// - The returned KV handle is only valid to access the key and value, + /// and only valid until the next call to a `deallocating_` method. + unsafe fn deallocating_next_back<A: Allocator + Clone>( + self, + alloc: A, + ) -> Option<(Self, Handle<NodeRef<marker::Dying, K, V, marker::LeafOrInternal>, marker::KV>)> + { + let mut edge = self.forget_node_type(); + loop { + edge = match edge.left_kv() { + Ok(kv) => return Some((unsafe { ptr::read(&kv) }.next_back_leaf_edge(), kv)), + Err(last_edge) => { + match unsafe { last_edge.into_node().deallocate_and_ascend(alloc.clone()) } { + Some(parent_edge) => parent_edge.forget_node_type(), + None => return None, + } + } + } + } + } + + /// Deallocates a pile of nodes from the leaf up to the root. + /// This is the only way to deallocate the remainder of a tree after + /// `deallocating_next` and `deallocating_next_back` have been nibbling at + /// both sides of the tree, and have hit the same edge. As it is intended + /// only to be called when all keys and values have been returned, + /// no cleanup is done on any of the keys or values. + fn deallocating_end<A: Allocator + Clone>(self, alloc: A) { + let mut edge = self.forget_node_type(); + while let Some(parent_edge) = + unsafe { edge.into_node().deallocate_and_ascend(alloc.clone()) } + { + edge = parent_edge.forget_node_type(); + } + } +} + +impl<'a, K, V> Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge> { + /// Moves the leaf edge handle to the next leaf edge and returns references to the + /// key and value in between. + /// + /// # Safety + /// There must be another KV in the direction travelled. + unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) { + super::mem::replace(self, |leaf_edge| { + let kv = leaf_edge.next_kv().ok().unwrap(); + (kv.next_leaf_edge(), kv.into_kv()) + }) + } + + /// Moves the leaf edge handle to the previous leaf edge and returns references to the + /// key and value in between. + /// + /// # Safety + /// There must be another KV in the direction travelled. + unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) { + super::mem::replace(self, |leaf_edge| { + let kv = leaf_edge.next_back_kv().ok().unwrap(); + (kv.next_back_leaf_edge(), kv.into_kv()) + }) + } +} + +impl<'a, K, V> Handle<NodeRef<marker::ValMut<'a>, K, V, marker::Leaf>, marker::Edge> { + /// Moves the leaf edge handle to the next leaf edge and returns references to the + /// key and value in between. + /// + /// # Safety + /// There must be another KV in the direction travelled. + unsafe fn next_unchecked(&mut self) -> (&'a K, &'a mut V) { + let kv = super::mem::replace(self, |leaf_edge| { + let kv = leaf_edge.next_kv().ok().unwrap(); + (unsafe { ptr::read(&kv) }.next_leaf_edge(), kv) + }); + // Doing this last is faster, according to benchmarks. + kv.into_kv_valmut() + } + + /// Moves the leaf edge handle to the previous leaf and returns references to the + /// key and value in between. + /// + /// # Safety + /// There must be another KV in the direction travelled. + unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) { + let kv = super::mem::replace(self, |leaf_edge| { + let kv = leaf_edge.next_back_kv().ok().unwrap(); + (unsafe { ptr::read(&kv) }.next_back_leaf_edge(), kv) + }); + // Doing this last is faster, according to benchmarks. + kv.into_kv_valmut() + } +} + +impl<K, V> Handle<NodeRef<marker::Dying, K, V, marker::Leaf>, marker::Edge> { + /// Moves the leaf edge handle to the next leaf edge and returns the key and value + /// in between, deallocating any node left behind while leaving the corresponding + /// edge in its parent node dangling. + /// + /// # Safety + /// - There must be another KV in the direction travelled. + /// - That KV was not previously returned by counterpart + /// `deallocating_next_back_unchecked` on any copy of the handles + /// being used to traverse the tree. + /// + /// The only safe way to proceed with the updated handle is to compare it, drop it, + /// or call this method or counterpart `deallocating_next_back_unchecked` again. + unsafe fn deallocating_next_unchecked<A: Allocator + Clone>( + &mut self, + alloc: A, + ) -> Handle<NodeRef<marker::Dying, K, V, marker::LeafOrInternal>, marker::KV> { + super::mem::replace(self, |leaf_edge| unsafe { + leaf_edge.deallocating_next(alloc).unwrap() + }) + } + + /// Moves the leaf edge handle to the previous leaf edge and returns the key and value + /// in between, deallocating any node left behind while leaving the corresponding + /// edge in its parent node dangling. + /// + /// # Safety + /// - There must be another KV in the direction travelled. + /// - That leaf edge was not previously returned by counterpart + /// `deallocating_next_unchecked` on any copy of the handles + /// being used to traverse the tree. + /// + /// The only safe way to proceed with the updated handle is to compare it, drop it, + /// or call this method or counterpart `deallocating_next_unchecked` again. + unsafe fn deallocating_next_back_unchecked<A: Allocator + Clone>( + &mut self, + alloc: A, + ) -> Handle<NodeRef<marker::Dying, K, V, marker::LeafOrInternal>, marker::KV> { + super::mem::replace(self, |leaf_edge| unsafe { + leaf_edge.deallocating_next_back(alloc).unwrap() + }) + } +} + +impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V, marker::LeafOrInternal> { + /// Returns the leftmost leaf edge in or underneath a node - in other words, the edge + /// you need first when navigating forward (or last when navigating backward). + #[inline] + pub fn first_leaf_edge(self) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> { + let mut node = self; + loop { + match node.force() { + Leaf(leaf) => return leaf.first_edge(), + Internal(internal) => node = internal.first_edge().descend(), + } + } + } + + /// Returns the rightmost leaf edge in or underneath a node - in other words, the edge + /// you need last when navigating forward (or first when navigating backward). + #[inline] + pub fn last_leaf_edge(self) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> { + let mut node = self; + loop { + match node.force() { + Leaf(leaf) => return leaf.last_edge(), + Internal(internal) => node = internal.last_edge().descend(), + } + } + } +} + +pub enum Position<BorrowType, K, V> { + Leaf(NodeRef<BorrowType, K, V, marker::Leaf>), + Internal(NodeRef<BorrowType, K, V, marker::Internal>), + InternalKV(Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::KV>), +} + +impl<'a, K: 'a, V: 'a> NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal> { + /// Visits leaf nodes and internal KVs in order of ascending keys, and also + /// visits internal nodes as a whole in a depth first order, meaning that + /// internal nodes precede their individual KVs and their child nodes. + pub fn visit_nodes_in_order<F>(self, mut visit: F) + where + F: FnMut(Position<marker::Immut<'a>, K, V>), + { + match self.force() { + Leaf(leaf) => visit(Position::Leaf(leaf)), + Internal(internal) => { + visit(Position::Internal(internal)); + let mut edge = internal.first_edge(); + loop { + edge = match edge.descend().force() { + Leaf(leaf) => { + visit(Position::Leaf(leaf)); + match edge.next_kv() { + Ok(kv) => { + visit(Position::InternalKV(kv)); + kv.right_edge() + } + Err(_) => return, + } + } + Internal(internal) => { + visit(Position::Internal(internal)); + internal.first_edge() + } + } + } + } + } + } + + /// Calculates the number of elements in a (sub)tree. + pub fn calc_length(self) -> usize { + let mut result = 0; + self.visit_nodes_in_order(|pos| match pos { + Position::Leaf(node) => result += node.len(), + Position::Internal(node) => result += node.len(), + Position::InternalKV(_) => (), + }); + result + } +} + +impl<BorrowType: marker::BorrowType, K, V> + Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> +{ + /// Returns the leaf edge closest to a KV for forward navigation. + pub fn next_leaf_edge(self) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> { + match self.force() { + Leaf(leaf_kv) => leaf_kv.right_edge(), + Internal(internal_kv) => { + let next_internal_edge = internal_kv.right_edge(); + next_internal_edge.descend().first_leaf_edge() + } + } + } + + /// Returns the leaf edge closest to a KV for backward navigation. + fn next_back_leaf_edge(self) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> { + match self.force() { + Leaf(leaf_kv) => leaf_kv.left_edge(), + Internal(internal_kv) => { + let next_internal_edge = internal_kv.left_edge(); + next_internal_edge.descend().last_leaf_edge() + } + } + } +} |