From 55fa8afe94019cb1da29d5fab7fd7ad5795b2c39 Mon Sep 17 00:00:00 2001 From: Stein Somers Date: Sun, 9 Aug 2020 12:25:20 +0200 Subject: [PATCH] BTreeMap: various tweaks --- library/alloc/src/collections/btree/node.rs | 111 +++++++++----------- 1 file changed, 50 insertions(+), 61 deletions(-) diff --git a/library/alloc/src/collections/btree/node.rs b/library/alloc/src/collections/btree/node.rs index 3ce5dfbc4dc..c3f27c10599 100644 --- a/library/alloc/src/collections/btree/node.rs +++ b/library/alloc/src/collections/btree/node.rs @@ -47,8 +47,7 @@ const KV_IDX_CENTER: usize = B - 1; const EDGE_IDX_LEFT_OF_CENTER: usize = B - 1; const EDGE_IDX_RIGHT_OF_CENTER: usize = B; -/// The underlying representation of leaf nodes. -#[repr(C)] +/// The underlying representation of leaf nodes and part of the representation of internal nodes. struct LeafNode { /// We want to be covariant in `K` and `V`. parent: Option>>, @@ -59,9 +58,6 @@ struct LeafNode { parent_idx: MaybeUninit, /// The number of keys and values this node stores. - /// - /// This next to `parent_idx` to encourage the compiler to join `len` and - /// `parent_idx` into the same 32-bit word, reducing space overhead. len: u16, /// The arrays storing the actual data of the node. Only the first `len` elements of each @@ -92,7 +88,9 @@ impl LeafNode { /// node, allowing code to act on leaf and internal nodes generically without having to even check /// which of the two a pointer is pointing at. This property is enabled by the use of `repr(C)`. #[repr(C)] +// gdb_providers.py uses this type name for introspection. struct InternalNode { + // gdb_providers.py uses this field name for introspection. data: LeafNode, /// The pointers to the children of this node. `len + 1` of these are considered @@ -183,9 +181,9 @@ impl Root { NodeRef { height: self.height, node: self.node.as_ptr(), _marker: PhantomData } } - /// Adds a new internal node with a single edge, pointing to the previous root, and make that - /// new node the root. This increases the height by 1 and is the opposite of - /// `pop_internal_level`. + /// Adds a new internal node with a single edge pointing to the previous root node, + /// make that new node the root node, and return it. This increases the height by 1 + /// and is the opposite of `pop_internal_level`. pub fn push_internal_level(&mut self) -> NodeRef, K, V, marker::Internal> { let mut new_node = Box::new(unsafe { InternalNode::new() }); new_node.edges[0].write(unsafe { BoxedNode::from_ptr(self.node.as_ptr()) }); @@ -322,7 +320,7 @@ impl NodeRef { NodeRef { height: self.height, node: self.node, _marker: PhantomData } } - /// Exposes the leaf "portion" of any leaf or internal node. + /// Exposes the leaf portion of any leaf or internal node. /// If the node is a leaf, this function simply opens up its data. /// If the node is an internal node, so not a leaf, it does have all the data a leaf has /// (header, keys and values), and this function exposes that. @@ -472,7 +470,7 @@ impl<'a, K, V, Type> NodeRef, K, V, Type> { NodeRef { height: self.height, node: self.node, _marker: PhantomData } } - /// Exposes the leaf "portion" of any leaf or internal node for writing. + /// Exposes the leaf portion of any leaf or internal node for writing. /// If the node is a leaf, this function simply opens up its data. /// If the node is an internal node, so not a leaf, it does have all the data a leaf has /// (header, keys and values), and this function exposes that. @@ -498,18 +496,38 @@ impl<'a, K, V, Type> NodeRef, K, V, Type> { unsafe { self.reborrow_mut().into_val_mut_at(idx) } } - fn keys_mut(&mut self) -> &mut [K] { + fn keys_mut(&mut self) -> &mut [K] + where + K: 'a, + V: 'a, + { // SAFETY: the caller will not be able to call further methods on self // until the key slice reference is dropped, as we have unique access // for the lifetime of the borrow. - unsafe { self.reborrow_mut().into_key_slice_mut() } + // SAFETY: The keys of a node must always be initialized up to length. + unsafe { + slice::from_raw_parts_mut( + MaybeUninit::slice_as_mut_ptr(&mut self.as_leaf_mut().keys), + self.len(), + ) + } } - fn vals_mut(&mut self) -> &mut [V] { + fn vals_mut(&mut self) -> &mut [V] + where + K: 'a, + V: 'a, + { // SAFETY: the caller will not be able to call further methods on self // until the value slice reference is dropped, as we have unique access // for the lifetime of the borrow. - unsafe { self.reborrow_mut().into_val_slice_mut() } + // SAFETY: The values of a node must always be initialized up to length. + unsafe { + slice::from_raw_parts_mut( + MaybeUninit::slice_as_mut_ptr(&mut self.as_leaf_mut().vals), + self.len(), + ) + } } } @@ -539,26 +557,6 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef, K, V, Type> { } impl<'a, K: 'a, V: 'a, Type> NodeRef, K, V, Type> { - fn into_key_slice_mut(mut self) -> &'a mut [K] { - // SAFETY: The keys of a node must always be initialized up to length. - unsafe { - slice::from_raw_parts_mut( - MaybeUninit::slice_as_mut_ptr(&mut self.as_leaf_mut().keys), - self.len(), - ) - } - } - - fn into_val_slice_mut(mut self) -> &'a mut [V] { - // SAFETY: The values of a node must always be initialized up to length. - unsafe { - slice::from_raw_parts_mut( - MaybeUninit::slice_as_mut_ptr(&mut self.as_leaf_mut().vals), - self.len(), - ) - } - } - /// # Safety /// The node has more than `idx` initialized elements. unsafe fn into_key_mut_at(mut self, idx: usize) -> &'a mut K { @@ -610,8 +608,8 @@ impl<'a, K: 'a, V: 'a> NodeRef, K, V, marker::Leaf> { } /// Adds a key/value pair to the beginning of the node. - pub fn push_front(&mut self, key: K, val: V) { - assert!(self.len() < CAPACITY); + fn push_front(&mut self, key: K, val: V) { + debug_assert!(self.len() < CAPACITY); unsafe { slice_insert(self.keys_mut(), 0, key); @@ -683,10 +681,9 @@ impl<'a, K: 'a, V: 'a> NodeRef, K, V, marker::Internal> { impl<'a, K: 'a, V: 'a> NodeRef, K, V, marker::LeafOrInternal> { /// Removes a key/value pair from the end of this node and returns the pair. /// If this is an internal node, also removes the edge that was to the right - /// of that pair and returns the orphaned node that this edge owned with its - /// parent erased. - pub fn pop(&mut self) -> (K, V, Option>) { - assert!(self.len() > 0); + /// of that pair and returns the orphaned node that this edge owned. + fn pop(&mut self) -> (K, V, Option>) { + debug_assert!(self.len() > 0); let idx = self.len() - 1; @@ -708,10 +705,11 @@ impl<'a, K: 'a, V: 'a> NodeRef, K, V, marker::LeafOrInternal> { } } - /// Removes a key/value pair from the beginning of this node. If this is an internal node, - /// also removes the edge that was to the left of that pair. - pub fn pop_front(&mut self) -> (K, V, Option>) { - assert!(self.len() > 0); + /// Removes a key/value pair from the beginning of this node and returns the pair. + /// If this is an internal node, also removes the edge that was to the left + /// of that pair and returns the orphaned node that this edge owned. + fn pop_front(&mut self) -> (K, V, Option>) { + debug_assert!(self.len() > 0); let old_len = self.len(); @@ -913,7 +911,6 @@ impl<'a, K: 'a, V: 'a, NodeType> Handle, K, V, NodeType> /// this edge. This method assumes that there is enough space in the node for the new /// pair to fit. fn leafy_insert_fit(&mut self, key: K, val: V) { - // Necessary for correctness, but in a private module debug_assert!(self.node.len() < CAPACITY); unsafe { @@ -951,18 +948,18 @@ impl<'a, K: 'a, V: 'a> Handle, K, V, marker::Leaf>, mark let (middle_kv_idx, insertion) = splitpoint(self.idx); let middle = unsafe { Handle::new_kv(self.node, middle_kv_idx) }; let (mut left, k, v, mut right) = middle.split(); - let val_ptr = match insertion { + let mut insertion_edge = match insertion { InsertionPlace::Left(insert_idx) => unsafe { - Handle::new_edge(left.reborrow_mut(), insert_idx).insert_fit(key, val) + Handle::new_edge(left.reborrow_mut(), insert_idx) }, InsertionPlace::Right(insert_idx) => unsafe { Handle::new_edge( right.node_as_mut().cast_unchecked::(), insert_idx, ) - .insert_fit(key, val) }, }; + let val_ptr = insertion_edge.insert_fit(key, val); (InsertResult::Split(SplitResult { left: left.forget_type(), k, v, right }), val_ptr) } } @@ -985,8 +982,6 @@ impl<'a, K: 'a, V: 'a> Handle, K, V, marker::Internal>, /// between this edge and the key/value pair to the right of this edge. This method assumes /// that there is enough space in the node for the new pair to fit. fn insert_fit(&mut self, key: K, val: V, edge: Root) { - // Necessary for correctness, but in an internal module - debug_assert!(self.node.len() < CAPACITY); debug_assert!(edge.height == self.node.height - 1); unsafe { @@ -1136,12 +1131,12 @@ impl<'a, K: 'a, V: 'a, NodeType> Handle, K, V, NodeType> ptr::copy_nonoverlapping( self.node.key_at(self.idx + 1), - new_node.keys.as_mut_ptr() as *mut K, + MaybeUninit::slice_as_mut_ptr(&mut new_node.keys), new_len, ); ptr::copy_nonoverlapping( self.node.val_at(self.idx + 1), - new_node.vals.as_mut_ptr() as *mut V, + MaybeUninit::slice_as_mut_ptr(&mut new_node.vals), new_len, ); @@ -1376,9 +1371,7 @@ impl<'a, K: 'a, V: 'a> Handle, K, V, marker::Internal>, move_edges(left, new_left_len + 1, right, 0, count); } (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {} - _ => { - unreachable!(); - } + _ => unreachable!(), } } } @@ -1433,9 +1426,7 @@ impl<'a, K: 'a, V: 'a> Handle, K, V, marker::Internal>, right.correct_childrens_parent_links(0..=new_right_len); } (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {} - _ => { - unreachable!(); - } + _ => unreachable!(), } } } @@ -1568,9 +1559,7 @@ impl<'a, K, V> Handle, K, V, marker::LeafOrInternal>, ma move_edges(left, left_new_len + 1, right, 1, right_new_len); } (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {} - _ => { - unreachable!(); - } + _ => unreachable!(), } } }