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-rw-r--r--graph/src/labelled/single.rs343
1 files changed, 343 insertions, 0 deletions
diff --git a/graph/src/labelled/single.rs b/graph/src/labelled/single.rs
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+//! This file implements a labelled graph that can index vertices by
+//! labels.
+//!
+//! Since we do not have to index edges by labels, the labels can be
+//! stored simply by adjacency maps. This may save memory usage and
+//! improve performance, potentially.
+
+use super::*;
+
+use std::collections::{hash_map::Keys, HashMap as Map};
+
+use crate::builder::BuilderMut;
+
+/// The type of a node.
+#[derive(Debug, Clone, Default)]
+struct SLNode<T: GraphLabel> {
+ /// The edges are stored as an association from the target node
+ /// index to the label of the corresponding edge.
+ ///
+ /// An implication is that an edge can only have one label.
+ children: Map<usize, T>,
+ /// The label of this node.
+ label: T,
+}
+
+impl<T: GraphLabel> SLNode<T> {
+ fn new(children: Map<usize, T>, label: T) -> Self {
+ Self { children, label }
+ }
+
+ /// This function just adds an edge, blindly.
+ ///
+ /// # Safety
+ ///
+ /// Only use this after making sure that `target` refers to a
+ /// valid node, and there was no edge from this node to the node
+ /// pointed to by `target` previously.
+ unsafe fn add_edge(&mut self, target: usize, label: T) {
+ self.children.insert(target, label);
+ }
+}
+
+/// The type of labelled graphs implemented using adjacency maps.
+#[derive(Debug, Clone)]
+pub struct SLGraph<T: GraphLabel> {
+ nodes: Vec<SLNode<T>>,
+ label_index_map: Map<T, usize>,
+}
+
+impl<T: GraphLabel> Default for SLGraph<T> {
+ fn default() -> Self {
+ let nodes = Vec::new();
+ let label_index_map = Default::default();
+ Self {
+ nodes,
+ label_index_map,
+ }
+ }
+}
+
+impl<T: GraphLabel> Graph for SLGraph<T> {
+ type Iter<'a> = std::iter::Copied<Keys<'a, usize, T>>
+ where
+ Self: 'a;
+
+ #[inline]
+ fn is_empty(&self) -> bool {
+ self.nodes.is_empty()
+ }
+
+ #[inline]
+ fn nodes_len(&self) -> usize {
+ self.nodes.len()
+ }
+
+ #[inline]
+ fn children_of(&self, node_id: usize) -> Result<Self::Iter<'_>, Error> {
+ if let Some(node) = self.nodes.get(node_id) {
+ Ok(node.children.keys().copied())
+ } else {
+ Err(Error::IndexOutOfBounds(node_id, self.nodes.len()))
+ }
+ }
+
+ #[inline]
+ fn degree(&self, node_id: usize) -> Result<usize, Error> {
+ if let Some(node) = self.nodes.get(node_id) {
+ Ok(node.children.len())
+ } else {
+ Err(Error::IndexOutOfBounds(node_id, self.nodes.len()))
+ }
+ }
+
+ #[inline]
+ fn is_empty_node(&self, node_id: usize) -> Result<bool, Error> {
+ if let Some(node) = self.nodes.get(node_id) {
+ Ok(node.children.is_empty())
+ } else {
+ Err(Error::IndexOutOfBounds(node_id, self.nodes.len()))
+ }
+ }
+
+ #[inline]
+ fn has_edge(&self, source: usize, target: usize) -> Result<bool, Error> {
+ let nodes_len = self.nodes.len();
+
+ let node = if let Some(node) = self.nodes.get(source) {
+ node
+ } else {
+ return Err(Error::IndexOutOfBounds(source, nodes_len));
+ };
+
+ if !self.has_node(target) {
+ return Err(Error::IndexOutOfBounds(target, nodes_len));
+ }
+
+ Ok(node.children.contains_key(&target))
+ }
+
+ fn replace_by_builder(&mut self, _builder: impl Builder<Result = Self>) {
+ // In case this is not clear enough, I deliberately avoid
+ // implementing this.
+ unimplemented!()
+ }
+}
+
+/// An iterator of edge labels.
+///
+/// This is used to avoid a box allocation.
+#[derive(Copy, Clone, Debug)]
+pub struct EdgeLabelIter<T: GraphLabel>(Option<T>);
+
+impl<T: GraphLabel> Iterator for EdgeLabelIter<T> {
+ type Item = T;
+
+ #[inline]
+ fn next(&mut self) -> Option<Self::Item> {
+ self.0.take()
+ }
+
+ #[inline]
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ let len = self.0.is_some() as usize;
+
+ (len, Some(len))
+ }
+}
+
+impl<T: GraphLabel> DoubleEndedIterator for EdgeLabelIter<T> {
+ #[inline]
+ fn next_back(&mut self) -> Option<Self::Item> {
+ self.0.take()
+ }
+}
+
+impl<T: GraphLabel> ExactSizeIterator for EdgeLabelIter<T> {
+ #[inline]
+ fn len(&self) -> usize {
+ // Thanks to Clippy for teaching me about coercing a boolean
+ // value to an integer.
+ self.0.is_some() as usize
+ }
+}
+
+impl<T: GraphLabel> LabelGraph<T> for SLGraph<T> {
+ // The following two types are not used, as we do not need to
+ // index edges by labels.
+ type Iter<'a> = std::iter::Empty<usize>
+ where
+ Self: 'a;
+
+ type LabelIter<'a> = std::iter::Empty<(&'a T, <Self as LabelGraph<T>>::Iter<'a>)>
+ where
+ Self: 'a,
+ T: 'a;
+
+ type EdgeLabelIter<'a> = EdgeLabelIter<T>
+ where
+ Self: 'a,
+ T: 'a;
+
+ #[inline]
+ fn query_label(&self, label: T) -> Option<usize> {
+ self.label_index_map.get(&label).copied()
+ }
+
+ #[inline]
+ fn vertex_label(&self, node_id: usize) -> Result<Option<T>, Error> {
+ if let Some(node) = self.nodes.get(node_id) {
+ Ok(Some(node.label))
+ } else {
+ Err(Error::IndexOutOfBounds(node_id, self.nodes_len()))
+ }
+ }
+
+ #[inline]
+ fn edge_label(&self, source: usize, target: usize) -> Result<Self::EdgeLabelIter<'_>, Error> {
+ let nodes_len = self.nodes.len();
+
+ let node = if let Some(node) = self.nodes.get(source) {
+ node
+ } else {
+ return Err(Error::IndexOutOfBounds(source, nodes_len));
+ };
+
+ if !self.has_node(target) {
+ return Err(Error::IndexOutOfBounds(target, nodes_len));
+ }
+
+ Ok(EdgeLabelIter(node.children.get(&target).copied()))
+ }
+
+ fn find_children_with_label(
+ &self,
+ _node_id: usize,
+ _label: &T,
+ ) -> Result<<Self as LabelGraph<T>>::Iter<'_>, Error> {
+ unimplemented!()
+ }
+
+ fn labels_of(&self, _node_id: usize) -> Result<Self::LabelIter<'_>, Error> {
+ unimplemented!()
+ }
+
+ #[inline]
+ fn has_edge_label(&self, node_id: usize, label: &T, target: usize) -> Result<bool, Error> {
+ let nodes_len = self.nodes.len();
+
+ let node = if let Some(node) = self.nodes.get(node_id) {
+ node
+ } else {
+ return Err(Error::IndexOutOfBounds(node_id, nodes_len));
+ };
+
+ if !self.has_node(target) {
+ return Err(Error::IndexOutOfBounds(target, nodes_len));
+ }
+
+ Ok(node.children.get(&target) == Some(label))
+ }
+}
+
+/// The type of `builder_mut` builders for this type of graphs.
+#[derive(Debug)]
+pub struct SLGBuilderMut<'a, T: GraphLabel> {
+ graph: &'a mut SLGraph<T>,
+}
+
+impl<'a, T: GraphLabel> BuilderMut for SLGBuilderMut<'a, T> {
+ type Label = T;
+
+ type Graph = SLGraph<T>;
+
+ type ResultBuilder<'b> = SLGBuilderMut<'b, T>
+ where
+ T:'b;
+
+ fn from_graph_mut(graph: &mut Self::Graph) -> Self::ResultBuilder<'_> {
+ SLGBuilderMut { graph }
+ }
+
+ fn add_vertex(&mut self, label: T) -> Result<usize, Error> {
+ if let Some(old_node) = self.graph.label_index_map.get(&label) {
+ dbg!(label);
+ return Err(Error::DuplicatedNode(*old_node));
+ }
+
+ self.graph
+ .nodes
+ .push(SLNode::new(Default::default(), label));
+
+ let new = self.graph.nodes_len() - 1;
+
+ self.graph.label_index_map.insert(label, new);
+
+ Ok(new)
+ }
+
+ fn add_edge(&mut self, source: usize, target: usize, label: Self::Label) -> Result<(), Error> {
+ let graph = &mut self.graph;
+
+ let nodes_len = graph.nodes.len();
+
+ // NOTE: We check the validity of `target` first because we
+ // need to borrow graph mutably later, which would prevent us
+ // from borrowing graph immutably to check the validity of
+ // `target` then.
+ if !graph.has_node(target) {
+ return Err(Error::IndexOutOfBounds(target, nodes_len));
+ }
+
+ let node = if let Some(node) = graph.nodes.get_mut(source) {
+ node
+ } else {
+ return Err(Error::IndexOutOfBounds(source, nodes_len));
+ };
+
+ if node.children.get(&target).is_some() {
+ return Err(Error::DuplicatedEdge(source, target));
+ }
+
+ // We checked what we need to check, so this is safe.
+ unsafe {
+ node.add_edge(target, label);
+ }
+
+ Ok(())
+ }
+
+ fn remove_edge<F>(&mut self, source: usize, target: usize, predicate: F) -> Result<(), Error>
+ where
+ F: Fn(Self::Label) -> bool,
+ {
+ let graph = &mut self.graph;
+
+ let nodes_len = graph.nodes.len();
+
+ // NOTE: We check the validity of `target` first because we
+ // need to borrow graph mutably later, which would prevent us
+ // from borrowing graph immutably to check the validity of
+ // `target` then.
+ if !graph.has_node(target) {
+ return Err(Error::IndexOutOfBounds(target, nodes_len));
+ }
+
+ let node = if let Some(node) = graph.nodes.get_mut(source) {
+ node
+ } else {
+ return Err(Error::IndexOutOfBounds(source, nodes_len));
+ };
+
+ if let Some(child_label) = node.children.get(&target) {
+ // There is only one label, so we just check this label.
+ if predicate(*child_label) {
+ node.children.remove(&target);
+ }
+
+ Ok(())
+ } else {
+ Err(Error::DuplicatedEdge(source, target))
+ }
+ }
+}
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