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//! Types for storing and exploring trees. #![deny(missing_docs)] /// An error returned when attempting to build a [`Sapling`]`<T>`. /// /// The error contains the sapling that failed to build in order to return it to /// the caller. Otherwise the [`build`] function would drop the sapling without /// returning a resulting [`Tree`]`<T>`. /// /// [`build`]: Sapling::build pub enum BuildError<T> { /// The sapling is incomplete and not ready to be built. /// /// It is either empty or there are still unclosed nodes. Use [`pop_all`] to /// close any unclosed nodes and use [`is_empty`] to check if th sapling is /// empty. /// /// [`is_empty`]: Sapling::is_empty /// [`pop_all`]: Sapling::pop_all Incomplete(Sapling<T>), /// The sapling contains more than one root node. /// /// When creating nodes on a sapling it is possible to [`pop`] the root node /// and [`push`] a second root. Trees however must have a unique root. /// /// To get an iterator over the root nodes build the sapling into a /// [`PolyTree`]`<T>` using [`build_polytree`]. /// /// [`build_polytree`]: Sapling::build_polytree /// [`pop`]: Sapling::pop /// [`push`]: Sapling::push MultipleRoots(Sapling<T>), } impl<T> std::fmt::Debug for BuildError<T> { fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { match self { Self::Incomplete(_) => write!(f, "Incomplete"), Self::MultipleRoots(_) => write!(f, "MultipleRoots"), } } } impl<T> std::fmt::Display for BuildError<T> { fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { match self { Self::Incomplete(_) => write!(f, "Incomplete tree structure"), Self::MultipleRoots(_) => write!(f, "Multiple roots in tree"), } } } impl<T> std::error::Error for BuildError<T> {} /// An error returned when validating a vertex slice. #[derive(Debug, PartialEq, Copy, Clone)] pub enum ValidationError { /// The vertex slice is empty. /// /// Nodes must always have exactly one root. The buffer therefor needs to /// have at least one entry. Empty, /// The vertex slice contains more than one root node. /// /// Nodes can only have exactly one root node. MultipleRoots, /// Some of the lengths of the vertices do not match up. Ensure a vertex /// does not have more descendants than its ancestors. IllegalStructure, } impl std::fmt::Display for ValidationError { fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { match self { Self::Empty => write!(f, "Empty vertex slice"), Self::MultipleRoots => write!(f, "Multiple roots in vertex slice"), Self::IllegalStructure => write!(f, "Vertex with invalid length"), } } } impl std::error::Error for ValidationError {} /// An internal type that stores the payload and relationships of a node in a /// [`Tree`]`<T>` or [`PolyTree`]`<T>`. /// /// Every node on the tree is represented by a [`Vertex`]`<T>`. The `len` field /// stores the number of descendants the node has; this is the number of nodes /// in the subtree below the node. A leaf node has length `0`. /// /// Every [`Tree`]`<T>` contains a [`Vec`]`<`[`Vertex`]`<T>>` representing the /// trees nodes in a depth first order; meaning every vertex is followed by its /// first child. This makes it very easy to take a slice of the vertex buffer /// that represents a subtree. We expose such a slice to the user as a /// [`Node`]`<T>`. /// /// The type implements [`Clone`] and [`Copy`] as long as the payload `T` /// implements the same. Supporting [`Copy`] is important to ensure /// [`Vec::extend_from_slice`] executes as fast as possible. This method is used /// by [`Sapling::push_tree`] to copy the nodes of a tree into another sapling. #[derive(Debug, Clone, Copy)] pub struct Vertex<T> { len: usize, data: T, } impl<T> Vertex<T> { /// Returns a new vertex with payload `data` intending to own `len` many /// descendants. pub fn new(data: T, len: usize) -> Self { Vertex { data, len } } } /// A builder to construct [`Tree`]`<T>`s and [`PolyTree`]`<T>`s. /// /// Saplings are the only way of creating a [`Tree`]`<T>`. New saplings are /// initialized empty, containing no nodes. Nodes are then added to the sapling /// until the tree is complete. The sapling can then be turned into a tree. /// /// Nodes are added to saplings using [`push`]. Adding a new node also selects /// it, meaning later calls of [`push`] will attach the new node as a child to /// this one. To close a node once all its child nodes have been added, call /// [`pop`]. /// /// When the sapling is complete, turn it into a [`Tree`]`<T>` using [`build`]. /// This method returns a [`Result`]`<`[`Tree`]`<T>, `[`BuildError`]`<T>>` to /// indicate if the sapling was built successfully. In case of an error /// [`BuildError`]`<T>` will contain the sapling. /// /// # Examples /// /// ```rust /// use read_tree::{Sapling, Tree}; /// /// fn main() -> Result<(), Box<dyn std::error::Error>> { /// let mut sap = Sapling::new(); /// assert!(sap.is_empty()); /// /// sap.push(1); // Add a new node to the tree carrying the payload `1`. /// sap.push_leaf(11); // Add a child node to node `1`. This node will have no children. /// sap.push(12); // Add another child node to `1`. Select this node. /// sap.push_leaf(121); // Add leaf nodes to node `12`. /// sap.push_leaf(122); /// /// sap.pop(); // Close node `12`. /// sap.pop(); // Close node `1`. /// /// assert!(sap.is_ready()); /// let _tree = sap.build()?; /// /// Ok(()) /// } /// ``` /// /// [`build`]: Sapling::build /// [`pop`]: Sapling::pop /// [`push`]: Sapling::push #[derive(Debug)] pub struct Sapling<T> { path: Vec<usize>, verts: Vec<Vertex<T>>, } impl<T> Sapling<T> { /// Creates a new empty sapling. /// /// An empty sapling is not yet ready to be built. Add at least one node /// before building it into a tree. /// /// # Examples /// /// ```rust /// use read_tree::Sapling; /// /// let sap = Sapling::<usize>::new(); /// assert!(sap.is_empty()); /// assert!(sap.build().is_err()); /// ``` pub fn new() -> Self { Sapling { path: Vec::new(), verts: Vec::new(), } } /// Creates a new empty sapling with enough capacity to store `len` many /// nodes. /// /// The sapling is allowed to receive more than `len` nodes; this may /// however cause further memory allocations. For more information check out /// [`Vec::with_capacity`]. /// /// The optional parameter `depth` should predict the maximum depth of the /// tree. If the depth is unknown use `None`. The depth should include the /// root node, can however exclude leaf nodes, if the leaf nodes will be /// added using [`push_leaf`]. The rule is that every call to [`push`] /// increases the depth, and every call to [`pop`] decreases it. Empty /// saplings start with depth `0` and methods like [`push_leaf`] do not /// affect the depth. If omitted `0` will be used by default. /// /// [`pop`]: Sapling::pop /// [`push_leaf`]: Sapling::push_leaf /// [`push`]: Sapling::push pub fn with_capacity(len: usize, depth: Option<usize>) -> Self { Sapling { path: Vec::with_capacity(depth.unwrap_or(0)), verts: Vec::with_capacity(len), } } /// Adds a new node with the payload `data` to the sapling. /// /// The new node is positioned as a child node of the currently selected /// node. The selected node will be changed to be the new node until the /// next call of [`pop`]. To avoid changing the selection use [`push_leaf`] /// instead; note that this will make it impossible to attach child nodes to /// the node, forcing it to be a leaf node. /// /// Nodes have to be added to the sapling in the correct oder. Once a node /// has been closed using [`pop`] its subtree is finalized and can no longer /// be changed. /// /// [`pop`]: Sapling::pop /// [`push_leaf`]: Sapling::push_leaf /// [`push`]: Sapling::push pub fn push(&mut self, data: T) { self.path.push(self.verts.len()); self.verts.push(Vertex { len: 0, data }); } /// Adds a new leaf node with the payload `data` to the sapling. /// /// This method is a convenient shortcut that behaves the same as calling /// [`push`] immediately followed by [`pop`]. /// /// [`pop`]: Sapling::pop /// [`push`]: Sapling::push pub fn push_leaf(&mut self, data: T) { self.verts.push(Vertex { len: 0, data }); } /// Adds another tree to the selected node in the sapling. This operation /// does not change the selected node, similar to [`push_leaf`]. /// /// Empties `tree` in the process and returns it as an empty sapling. This /// allows the caller to reuse the trees internal buffers. /// /// [`push_leaf`]: Sapling::push_leaf pub fn push_tree(&mut self, tree: Tree<T>) -> Sapling<T> { let mut sap = tree.into_sapling(); self.verts.append(&mut sap.verts); sap.clear(); sap } /// Adds another poly-tree to the selected node in the sapling. This /// operation does not change the selected node, similar to [`push_leaf`]. /// /// Empties `tree` in the process and returns it as an empty sapling. This /// allows the caller to reuse the trees internal buffers. /// /// [`push_leaf`]: Sapling::push_leaf pub fn push_polytree(&mut self, tree: PolyTree<T>) -> Sapling<T> { let mut sap = tree.into_sapling(); self.verts.append(&mut sap.verts); sap.clear(); sap } /// Clones the contents of a node and attaches the cloned subtree to the /// sapling. Requires the payload type `T` to be [`Clone`]. /// /// If `T` implements [`Copy`], the cloning of the subtree is relatively /// cheap. See [`Vec::extend_from_slice`] for more information. pub fn push_node(&mut self, node: Node<T>) where T: Clone, { self.verts.extend_from_slice(node.verts); } /// Returns a reference to the payload of the selected node. Returns `None` /// if no node is currently selected; this happens when the sapling is empty /// or after a root node was closed. /// /// # Examples /// /// ```rust /// use read_tree::Sapling; /// /// let mut sap = Sapling::new(); /// sap.push(0); /// sap.push(1); /// /// assert_eq!(sap.peek(), Some(&1)); /// assert_eq!(sap.pop(), Some(&1)); /// /// assert_eq!(sap.peek(), Some(&0)); /// assert_eq!(sap.pop(), Some(&0)); /// /// assert_eq!(sap.peek(), None); /// assert_eq!(sap.pop(), None); /// ``` pub fn peek(&self) -> Option<&T> { let i = *self.path.last()?; Some(&self.verts[i].data) } /// Closes the selected node. /// /// The subtree under the selected node is complete and will be closed. From /// then on new nodes will be attached to the parent of the closed node. /// /// Returns a reference to the payload of the closed node. Returns `None` if /// no node was selected; this happens when the sapling is empty or after a /// root node has been closed. /// /// # Examples /// /// ```rust /// use read_tree::Sapling; /// /// let mut sap = Sapling::new(); /// sap.push(0); /// assert_eq!(sap.pop(), Some(&0)); /// /// assert!(sap.is_ready()); /// ``` /// /// ```rust /// use read_tree::Sapling; /// /// let mut sap = Sapling::<usize>::new(); /// assert_eq!(sap.pop(), None); /// ``` pub fn pop(&mut self) -> Option<&T> { let i = self.path.pop()?; self.verts[i].len = self.verts.len() - i - 1; Some(&self.verts[i].data) } /// Closes all open nodes. /// /// # Examples /// /// ```rust /// use read_tree::Sapling; /// /// let mut sap = Sapling::new(); /// sap.push(0); /// sap.push(1); /// sap.push(2); /// sap.pop_all(); /// /// assert!(sap.is_ready()); /// ``` pub fn pop_all(&mut self) { while let Some(i) = self.path.pop() { self.verts[i].len = self.verts.len() - i - 1; } } /// Closes the current node and makes it a leaf node. /// /// Any nodes that were attached to the node will be attached to its parent /// instead. /// /// # Examples /// /// ```rust /// use read_tree::Sapling; /// /// let mut sap = Sapling::new(); /// sap.push(0); /// sap.push(1); /// sap.push_leaf(2); /// /// // make `1` a leaf node; changing `2` to be a child of `0` /// sap.pop_as_leaf(); /// sap.pop(); /// /// let tree = sap.build().unwrap(); /// let mut iter = tree.as_node().children(); /// /// assert_eq!(iter.next().unwrap().data(), &1); /// assert_eq!(iter.next().unwrap().data(), &2); /// assert!(iter.next().is_none()); /// ``` pub fn pop_as_leaf(&mut self) -> Option<&T> { let i = self.path.pop()?; Some(&self.verts[i].data) } /// Closes all open nodes and makes them all leaf nodes. /// /// If there are open nodes in the sapling, this will create multiple root /// nodes. /// /// # Examples /// /// ```rust /// use read_tree::{BuildError, Sapling}; /// /// let mut sap = Sapling::new(); /// sap.push(0); /// sap.push(1); /// /// sap.pop_as_leaf_all(); /// match sap.build().unwrap_err() { /// BuildError::MultipleRoots(_) => (), /// _ => panic!(), /// } /// ``` pub fn pop_as_leaf_all(&mut self) { self.path.clear(); } /// Removes all nodes from the sapling, making it empty. /// /// # Examples /// /// ```rust /// use read_tree::Sapling; /// /// let mut sap = Sapling::new(); /// sap.push_leaf(0); /// assert_eq!(sap.is_empty(), false); /// /// sap.clear(); /// assert_eq!(sap.is_empty(), true); /// ``` pub fn clear(&mut self) { self.path.clear(); self.verts.clear(); } /// Returns `true` if the sapling contains no nodes. Use [`push`] to add /// nodes. /// /// [`push`]: Sapling::push pub fn is_empty(&self) -> bool { self.verts.is_empty() } /// Return `true` if the sapling is ready to be built. /// /// Verifies that the sapling is not empty and has no open nodes. It does /// not verify the number of root nodes of the sapling. Building into a /// [`Tree`]`<T>` may still fail because trees do not allow multiple root /// nodes. pub fn is_ready(&self) -> bool { self.path.is_empty() && !self.verts.is_empty() } /// Builds the sapling into a [`Tree`]`<T>`. /// /// Consumes the sapling in the process. Fails when the sapling is /// incomplete or has multiple roots. When failing to build the sapling, the /// sapling is returned unmodified with the [`BuildError`]`<T>`. pub fn build(self) -> Result<Tree<T>, BuildError<T>> { if !self.is_ready() { return Err(BuildError::Incomplete(self)); } if self.verts[0].len < self.verts.len() - 1 { return Err(BuildError::MultipleRoots(self)); } Ok(Tree { path: self.path, verts: self.verts, }) } /// Builds the sapling into a [`PolyTree`]`<T>`. /// /// Consumes the sapling in the process. Fails when the sapling is /// incomplete. When failing to build the sapling, the sapling is returned /// unmodified with the [`BuildError`]`<T>`. pub fn build_polytree(self) -> Result<PolyTree<T>, BuildError<T>> { if !self.is_ready() { return Err(BuildError::Incomplete(self)); } Ok(PolyTree { path: self.path, verts: self.verts, }) } } impl<T> Default for Sapling<T> { fn default() -> Self { Self::new() } } /// A read-only tree data structure. /// /// Trees are created from [`Sapling`]`<T>`s. Most interactions with trees /// happen on slices of them called [`Node`]s. Get a node representing the /// entire tree using [`as_node`]. /// /// [`as_node`]: Tree::as_node #[derive(Debug)] pub struct Tree<T> { /// Unused buffer. /// /// The buffer was used by the sapling that was used to construct the tree. /// It is kept in case the tree is turned back into a sapling. path: Vec<usize>, verts: Vec<Vertex<T>>, } #[allow(clippy::len_without_is_empty)] impl<T> Tree<T> { /// Returns the unique root node of the tree representing the entire tree. /// /// You can think of this as taking the complete slice of the tree similar /// to `&vec[..]` for a [`Vec`]`<T>`. pub fn as_node(&self) -> Node<T> { Node { rank: 0, verts: &self.verts[..], } } /// Returns the node with the specified `rank`. pub fn get(&self, rank: usize) -> Option<Node<T>> { if rank >= self.verts.len() { return None; } Some(Node { rank, verts: &self.verts[..], }) } /// Returns the number of nodes in the tree. /// /// Because trees are required to have exactly one root node, the length /// will always be at least `1`. pub fn len(&self) -> usize { self.verts.len() } /// Turns the tree back into a sapling. No nodes are removed from the /// tree; building the returned sapling will result in the original tree. /// /// All internal buffers are reused, making this a cheap operation. The only /// cost of converting [`Sapling`]`<T>`s and [`Tree`]`<T>`s back and forth /// is the validation that occurs during [`build`]. /// /// [`build`]: Sapling::build pub fn into_sapling(self) -> Sapling<T> { Sapling { path: self.path, verts: self.verts, } } } /// A read-only poly-tree data structure. /// /// Similar to [`Tree`]`<T>` but allows multiple root nodes. #[derive(Debug)] pub struct PolyTree<T> { path: Vec<usize>, verts: Vec<Vertex<T>>, } #[allow(clippy::len_without_is_empty)] impl<T> PolyTree<T> { /// Returns an iterator over the root nodes of the poly-tree. pub fn roots(&self) -> Children<T> { Children { top: 0, bottom: self.verts.len(), verts: &self.verts[..], } } /// Returns the node with the specified `rank`. pub fn get(&self, rank: usize) -> Option<Node<T>> { if rank >= self.verts.len() { return None; } Some(Node { rank, verts: &self.verts[..], }) } /// Returns the number of nodes in the poly-tree. /// /// Because poly-trees are required to not be empty, the length will always /// be at least `1`. pub fn len(&self) -> usize { self.verts.len() } /// Turns the poly-tree back into a sapling. No nodes are removed from the /// tree; building the returned sapling will result in the original /// poly-tree. /// /// All internal buffers are reused, making this a cheap operation. The only /// cost of converting [`Sapling`]`<T>`s and [`PolyTree`]`<T>`s back and /// forth is the validation that occurs during [`build_polytree`]. /// /// [`build_polytree`]: Sapling::build_polytree pub fn into_sapling(self) -> Sapling<T> { Sapling { path: self.path, verts: self.verts, } } } /// A slice of a [`Tree`]`<T>` or [`PolyTree`]`<T>`. /// /// A node is essentially the same as a tree, except it does not own its data. /// /// Navigating the subtree of a node is done using iterators. /// /// *It is planned to add a query type that allows querying nodes from subtrees /// using chains of conditions. Currently only some basic iterators are /// available.* #[derive(Debug)] pub struct Node<'a, T> { rank: usize, verts: &'a [Vertex<T>], } impl<'a, T> Node<'a, T> { /// Turns a slice of vertices into a [`Node`]`<T>`, after performing some /// validations. /// /// Returns an error in case of a failed validation. For the possible errors /// see [`ValidationError`]. For a more detailed description of the /// validation process see the safety section for [`from_unchecked`]. /// /// To avoid running the validations; which have a significant cost for /// large trees; use the unsafe alternative [`from_unchecked`]. /// /// [`from_unchecked`]: Node::from_unchecked pub fn from(verts: &[Vertex<T>]) -> Result<Node<T>, ValidationError> { if verts.is_empty() { return Err(ValidationError::Empty); } if verts[0].len != verts.len() - 1 { return Err(ValidationError::MultipleRoots); } let mut path = Vec::new(); for (i, val) in verts.iter().enumerate() { while path.last() == Some(&i) { path.pop(); } let scope = i + val.len + 1; if path.last().map(|head| *head < scope) == Some(true) { return Err(ValidationError::IllegalStructure); } path.push(scope); } Ok(Node { rank: 0, verts }) } /// Returns a slice of vertices as a [`Node`]`<T>`. /// /// This is the unsafe alternative to [`from`] that skips all validations. /// /// # Safety /// /// The caller must guarantee that all expected qualities of the vertex /// slice are fulfilled. /// /// 1. The vertex slice must not be empty. /// 2. The first vertex must span the entire slice. /// /// This means that the `len` of the first vertex is equal to /// `verts.len() - 1`. /// /// 3. The scope of all vertices must be contained within the scope of its /// parent vertex /// /// Here `scope` refers to the range starting from a nodes index to the /// nodes index plus its `len` inclusive. /// /// [`from`]: Node::from pub unsafe fn from_unchecked(verts: &[Vertex<T>]) -> Node<T> { Node { rank: 0, verts } } /// Returns a reference to the payload of the node. pub fn data(self) -> &'a T { &self.verts[self.rank].data } /// Returns the rank of the node in the tree. The rank can be used to look /// up the node from the tree using [`get`]. /// /// The rank also exposes information about the structure of the tree. Any /// node `child` with a rank greater than that of a node `parent` but not /// exceeding `parent.rank() + parent.len()` is a descendant of `parent`. /// /// [`get`]: Tree::get pub fn rank(self) -> usize { self.rank } /// Returns the number of descending nodes within the subtree of this node. /// A leaf node returns length `0`. pub fn len(self) -> usize { self.verts[self.rank].len } /// Returns `true` if the node has no child nodes. pub fn is_empty(self) -> bool { self.verts[self.rank].len == 0 } /// Returns the node with the specified `rank`. /// /// The rank must be relative to the trees root, or the most recently pruned /// node. See [`isolated`] for more information. /// /// [`isolated`]: Node::isolated pub fn get(self, rank: usize) -> Option<Node<'a, T>> { if rank >= self.verts.len() { return None; } Some(Node { rank, verts: self.verts, }) } /// Returns the parent of the node or `None` if it does not have one. pub fn parent(self) -> Option<Node<'a, T>> { self.ancestors().next() } /// Returns an iterator over the child nodes of the node. See [`Children`] /// for more information about the iterator. pub fn children(self) -> Children<'a, T> { Children::from(self) } /// Returns a depth first iterator of nodes. It iterates all nodes in the /// subtree of the node, including the node itself. See [`Descendants`] for /// more information about the iterator. pub fn descendants(self) -> Descendants<'a, T> { Descendants::from(self) } /// Returns an iterator over the parent nodes. The parent of the node is /// first. The root of the tree is last. See [`Ancestors`] for more /// information about the iterator. pub fn ancestors(self) -> Ancestors<'a, T> { Ancestors::from(self) } /// Returns the nodes internal vertex slice. pub fn as_slice(self) -> &'a [Vertex<T>] { self.verts } /// Returns the node isolated from the rest of the tree. /// /// An isolated node will always have rank `0`, and it will be impossible to /// access its ancestors. It is still possible to explore the subtree below /// the node. /// /// When getting nodes by rank you must get them from this or any descending /// node. If you use the rank in a node that is not affected by this /// isolation, it will return some other node. Think of the isolated node as /// an entirely new tree with its own ranking. pub fn isolated(self) -> Node<'a, T> { Node { rank: 0, verts: &self.verts[self.rank..=self.rank + self.verts[self.rank].len], } } /// Clones the contents of the node into a new [`Tree`]`<T>`. /// /// Similar to [`push_node`] this operation is cheaper if `T` implements /// [`Copy`]. It is internally based on [`Vec::extend_from_slice`]. /// /// [`push_node`]: Sapling::push_node pub fn into_tree(self) -> Tree<T> where T: Clone, { let mut verts = Vec::new(); verts.extend_from_slice(self.verts); Tree { path: Vec::new(), verts, } } } impl<'a, T> Copy for Node<'a, T> {} impl<'a, T> Clone for Node<'a, T> { fn clone(&self) -> Self { *self } } /// Iterates the children of a node. /// /// # Examples /// /// ```rust /// use read_tree::Sapling; /// /// fn main() -> Result<(), Box<dyn std::error::Error>> { /// let mut sap = Sapling::new(); /// sap.push(1); /// sap.push_leaf(11); /// sap.push(12); /// sap.push_leaf(121); /// sap.pop(); /// sap.pop(); /// let tree = sap.build()?; /// let mut iter = tree.as_node().children(); /// /// assert_eq!(iter.next().unwrap().data(), &11); /// assert_eq!(iter.next().unwrap().data(), &12); /// assert!(iter.next().is_none()); /// /// Ok(()) /// } /// ``` #[derive(Debug)] pub struct Children<'a, T> { /// The next child node. top: usize, /// One beyond the last child node. bottom: usize, verts: &'a [Vertex<T>], } impl<'a, T> Children<'a, T> { /// Creates a new iterator over the children of a node. pub fn from(node: Node<'a, T>) -> Self { Children { top: node.rank() + 1, bottom: node.rank() + node.len() + 1, verts: node.verts, } } } impl<'a, T> Iterator for Children<'a, T> { type Item = Node<'a, T>; fn next(&mut self) -> Option<Self::Item> { if self.top >= self.bottom { return None; } let ret = Node { rank: self.top, verts: self.verts, }; self.top += self.verts[self.top].len + 1; Some(ret) } fn size_hint(&self) -> (usize, Option<usize>) { if self.top >= self.bottom { (0, Some(0)) } else { (1, Some(self.bottom - self.top)) } } } /// Iterates all descendants of a node depth first. /// /// The iterator implements [`ExactSizeIterator`] and [`DoubleEndedIterator`] /// giving access to [`len`] and [`rev`]. It also has fast implementations for /// [`nth`] and [`last`]. /// /// /// # Examples /// /// ```rust /// use read_tree::Sapling; /// /// fn main() -> Result<(), Box<dyn std::error::Error>> { /// let mut sap = Sapling::new(); /// sap.push(1); /// sap.push(11); /// sap.push_leaf(111); /// sap.pop(); /// sap.push(12); /// sap.push_leaf(121); /// sap.pop(); /// sap.pop(); /// let tree = sap.build()?; /// let mut iter = tree.as_node().descendants(); /// /// assert_eq!(iter.len(), 4); /// assert_eq!(iter.next().unwrap().data(), &11); /// assert_eq!(iter.next().unwrap().data(), &111); /// assert_eq!(iter.next().unwrap().data(), &12); /// assert_eq!(iter.next().unwrap().data(), &121); /// assert!(iter.next().is_none()); /// /// Ok(()) /// } /// ``` /// /// [`last`]: Iterator::last /// [`len`]: ExactSizeIterator::len /// [`nth`]: Iterator::nth /// [`rev`]: Iterator::rev #[derive(Debug)] pub struct Descendants<'a, T> { /// The next node to yield from the top. top: usize, /// The previously yielded node from the bottom bottom: usize, verts: &'a [Vertex<T>], } impl<'a, T> Descendants<'a, T> { /// Creates a new iterator over the descendants of a node. pub fn from(node: Node<'a, T>) -> Self { Descendants { top: node.rank() + 1, bottom: node.rank() + node.len() + 1, verts: node.verts, } } } impl<'a, T> Iterator for Descendants<'a, T> { type Item = Node<'a, T>; fn next(&mut self) -> Option<Self::Item> { if self.top >= self.bottom { return None; } let ret = Node { rank: self.top, verts: self.verts, }; self.top += 1; Some(ret) } fn nth(&mut self, n: usize) -> Option<Self::Item> { self.top += n; self.next() } fn last(mut self) -> Option<Self::Item> { self.next_back() } fn size_hint(&self) -> (usize, Option<usize>) { (self.len(), Some(self.len())) } fn count(self) -> usize { self.len() } } impl<'a, T> DoubleEndedIterator for Descendants<'a, T> { fn next_back(&mut self) -> Option<Self::Item> { if self.top >= self.bottom { return None; } self.bottom -= 1; Some(Node { rank: self.bottom, verts: self.verts, }) } } impl<'a, T> ExactSizeIterator for Descendants<'a, T> { fn len(&self) -> usize { self.bottom - self.top } } /// Iterates all ancestors of a node starting with the parent of the node. /// /// The iterator implements [`DoubleEndedIterator`], allowing it to be reversed /// using [`rev`]. /// /// [`rev`]: Iterator::rev #[derive(Debug)] pub struct Ancestors<'a, T> { /// The next potential top most ancestor. top: usize, /// The previously found bottom most ancestor. bottom: usize, verts: &'a [Vertex<T>], } impl<'a, T> Ancestors<'a, T> { /// Creates a new iterator over the ancestors of a node. pub fn from(node: Node<'a, T>) -> Self { Ancestors { top: 0, bottom: node.rank(), verts: node.verts, } } } impl<'a, T> Iterator for Ancestors<'a, T> { type Item = Node<'a, T>; fn next(&mut self) -> Option<Self::Item> { if self.top >= self.bottom { return None; } for i in (self.top..self.bottom).rev() { if self.bottom <= i + self.verts[i].len { self.bottom = i; return Some(Node { rank: i, verts: self.verts, }); } } None } fn size_hint(&self) -> (usize, Option<usize>) { (0, Some(self.top - self.bottom)) } fn count(self) -> usize { // The reverse direction of the iterator can skip subtrees and should therefor // be faster for most trees. self.rev().count() } fn last(mut self) -> Option<Self::Item> { self.next_back() } } impl<'a, T> DoubleEndedIterator for Ancestors<'a, T> { fn next_back(&mut self) -> Option<Self::Item> { let mut i = self.top; while i < self.bottom { let len = self.verts[i].len; if i + len < self.bottom { i += len + 1; } else { self.top = i + 1; return Some(Node { rank: i, verts: self.verts, }); } } None } }