1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! A graph module for use in dataflow, region resolution, and elsewhere.
13 //! # Interface details
15 //! You customize the graph by specifying a "node data" type `N` and an
16 //! "edge data" type `E`. You can then later gain access (mutable or
17 //! immutable) to these "user-data" bits. Currently, you can only add
18 //! nodes or edges to the graph. You cannot remove or modify them once
19 //! added. This could be changed if we have a need.
21 //! # Implementation details
23 //! The main tricky thing about this code is the way that edges are
24 //! stored. The edges are stored in a central array, but they are also
25 //! threaded onto two linked lists for each node, one for incoming edges
26 //! and one for outgoing edges. Note that every edge is a member of some
27 //! incoming list and some outgoing list. Basically you can load the
28 //! first index of the linked list from the node data structures (the
29 //! field `first_edge`) and then, for each edge, load the next index from
30 //! the field `next_edge`). Each of those fields is an array that should
31 //! be indexed by the direction (see the type `Direction`).
33 use bitvec::BitVector;
34 use std::fmt::{Formatter, Error, Debug};
36 use snapshot_vec::{SnapshotVec, SnapshotVecDelegate};
41 pub struct Graph<N, E> {
42 nodes: SnapshotVec<Node<N>>,
43 edges: SnapshotVec<Edge<E>>,
47 first_edge: [EdgeIndex; 2], // see module comment
52 next_edge: [EdgeIndex; 2], // see module comment
58 impl<N> SnapshotVecDelegate for Node<N> {
62 fn reverse(_: &mut Vec<Node<N>>, _: ()) {}
65 impl<N> SnapshotVecDelegate for Edge<N> {
69 fn reverse(_: &mut Vec<Edge<N>>, _: ()) {}
72 impl<E: Debug> Debug for Edge<E> {
73 fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
75 "Edge {{ next_edge: [{:?}, {:?}], source: {:?}, target: {:?}, data: {:?} }}",
84 #[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
85 pub struct NodeIndex(pub usize);
87 #[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
88 pub struct EdgeIndex(pub usize);
90 pub const INVALID_EDGE_INDEX: EdgeIndex = EdgeIndex(usize::MAX);
92 // Use a private field here to guarantee no more instances are created:
93 #[derive(Copy, Clone, Debug, PartialEq)]
94 pub struct Direction {
98 pub const OUTGOING: Direction = Direction { repr: 0 };
100 pub const INCOMING: Direction = Direction { repr: 1 };
103 /// Returns unique id (unique with respect to the graph holding associated node).
104 pub fn node_id(&self) -> usize {
109 impl<N: Debug, E: Debug> Graph<N, E> {
110 pub fn new() -> Graph<N, E> {
112 nodes: SnapshotVec::new(),
113 edges: SnapshotVec::new(),
117 // # Simple accessors
120 pub fn all_nodes(&self) -> &[Node<N>] {
125 pub fn len_nodes(&self) -> usize {
130 pub fn all_edges(&self) -> &[Edge<E>] {
135 pub fn len_edges(&self) -> usize {
139 // # Node construction
141 pub fn next_node_index(&self) -> NodeIndex {
142 NodeIndex(self.nodes.len())
145 pub fn add_node(&mut self, data: N) -> NodeIndex {
146 let idx = self.next_node_index();
147 self.nodes.push(Node {
148 first_edge: [INVALID_EDGE_INDEX, INVALID_EDGE_INDEX],
154 pub fn mut_node_data(&mut self, idx: NodeIndex) -> &mut N {
155 &mut self.nodes[idx.0].data
158 pub fn node_data(&self, idx: NodeIndex) -> &N {
159 &self.nodes[idx.0].data
162 pub fn node(&self, idx: NodeIndex) -> &Node<N> {
166 // # Edge construction and queries
168 pub fn next_edge_index(&self) -> EdgeIndex {
169 EdgeIndex(self.edges.len())
172 pub fn add_edge(&mut self, source: NodeIndex, target: NodeIndex, data: E) -> EdgeIndex {
173 debug!("graph: add_edge({:?}, {:?}, {:?})", source, target, data);
175 let idx = self.next_edge_index();
177 // read current first of the list of edges from each node
178 let source_first = self.nodes[source.0].first_edge[OUTGOING.repr];
179 let target_first = self.nodes[target.0].first_edge[INCOMING.repr];
181 // create the new edge, with the previous firsts from each node
182 // as the next pointers
183 self.edges.push(Edge {
184 next_edge: [source_first, target_first],
190 // adjust the firsts for each node target be the next object.
191 self.nodes[source.0].first_edge[OUTGOING.repr] = idx;
192 self.nodes[target.0].first_edge[INCOMING.repr] = idx;
197 pub fn edge(&self, idx: EdgeIndex) -> &Edge<E> {
201 // # Iterating over nodes, edges
203 pub fn enumerated_nodes(&self) -> EnumeratedNodes<N> {
205 iter: self.nodes.iter().enumerate()
209 pub fn enumerated_edges(&self) -> EnumeratedEdges<E> {
211 iter: self.edges.iter().enumerate()
215 pub fn each_node<'a, F>(&'a self, mut f: F) -> bool
216 where F: FnMut(NodeIndex, &'a Node<N>) -> bool
218 //! Iterates over all edges defined in the graph.
219 self.enumerated_nodes().all(|(node_idx, node)| f(node_idx, node))
222 pub fn each_edge<'a, F>(&'a self, mut f: F) -> bool
223 where F: FnMut(EdgeIndex, &'a Edge<E>) -> bool
225 //! Iterates over all edges defined in the graph
226 self.enumerated_edges().all(|(edge_idx, edge)| f(edge_idx, edge))
229 pub fn outgoing_edges(&self, source: NodeIndex) -> AdjacentEdges<N, E> {
230 self.adjacent_edges(source, OUTGOING)
233 pub fn incoming_edges(&self, source: NodeIndex) -> AdjacentEdges<N, E> {
234 self.adjacent_edges(source, INCOMING)
237 pub fn adjacent_edges(&self, source: NodeIndex, direction: Direction) -> AdjacentEdges<N, E> {
238 let first_edge = self.node(source).first_edge[direction.repr];
246 pub fn successor_nodes(&self, source: NodeIndex) -> AdjacentTargets<N, E> {
247 self.outgoing_edges(source).targets()
250 pub fn predecessor_nodes(&self, target: NodeIndex) -> AdjacentSources<N, E> {
251 self.incoming_edges(target).sources()
254 pub fn depth_traverse<'a>(&'a self,
256 direction: Direction)
257 -> DepthFirstTraversal<'a, N, E> {
258 DepthFirstTraversal::with_start_node(self, start, direction)
261 pub fn nodes_in_postorder<'a>(&'a self,
262 direction: Direction,
263 entry_node: NodeIndex)
266 let mut visited = BitVector::new(self.len_nodes());
267 let mut stack = vec![];
268 let mut result = Vec::with_capacity(self.len_nodes());
269 let mut push_node = |stack: &mut Vec<_>, node: NodeIndex| {
270 if visited.insert(node.0) {
271 stack.push((node, self.adjacent_edges(node, direction)));
275 for node in Some(entry_node).into_iter()
276 .chain(self.enumerated_nodes().map(|(node, _)| node))
278 push_node(&mut stack, node);
279 while let Some((node, mut iter)) = stack.pop() {
280 if let Some((_, child)) = iter.next() {
281 let target = child.source_or_target(direction);
282 // the current node needs more processing, so
283 // add it back to the stack
284 stack.push((node, iter));
285 // and then push the new node
286 push_node(&mut stack, target);
293 assert_eq!(result.len(), self.len_nodes());
300 pub struct EnumeratedNodes<'g, N>
303 iter: ::std::iter::Enumerate<::std::slice::Iter<'g, Node<N>>>
306 impl<'g, N: Debug> Iterator for EnumeratedNodes<'g, N> {
307 type Item = (NodeIndex, &'g Node<N>);
309 fn next(&mut self) -> Option<(NodeIndex, &'g Node<N>)> {
310 self.iter.next().map(|(idx, n)| (NodeIndex(idx), n))
314 pub struct EnumeratedEdges<'g, E>
317 iter: ::std::iter::Enumerate<::std::slice::Iter<'g, Edge<E>>>
320 impl<'g, E: Debug> Iterator for EnumeratedEdges<'g, E> {
321 type Item = (EdgeIndex, &'g Edge<E>);
323 fn next(&mut self) -> Option<(EdgeIndex, &'g Edge<E>)> {
324 self.iter.next().map(|(idx, e)| (EdgeIndex(idx), e))
328 pub struct AdjacentEdges<'g, N, E>
332 graph: &'g Graph<N, E>,
333 direction: Direction,
337 impl<'g, N, E> AdjacentEdges<'g, N, E> {
338 fn targets(self) -> AdjacentTargets<'g, N, E> {
339 AdjacentTargets { edges: self }
342 fn sources(self) -> AdjacentSources<'g, N, E> {
343 AdjacentSources { edges: self }
347 impl<'g, N: Debug, E: Debug> Iterator for AdjacentEdges<'g, N, E> {
348 type Item = (EdgeIndex, &'g Edge<E>);
350 fn next(&mut self) -> Option<(EdgeIndex, &'g Edge<E>)> {
351 let edge_index = self.next;
352 if edge_index == INVALID_EDGE_INDEX {
356 let edge = self.graph.edge(edge_index);
357 self.next = edge.next_edge[self.direction.repr];
358 Some((edge_index, edge))
362 pub struct AdjacentTargets<'g, N, E>
366 edges: AdjacentEdges<'g, N, E>,
369 impl<'g, N: Debug, E: Debug> Iterator for AdjacentTargets<'g, N, E> {
370 type Item = NodeIndex;
372 fn next(&mut self) -> Option<NodeIndex> {
373 self.edges.next().map(|(_, edge)| edge.target)
377 pub struct AdjacentSources<'g, N, E>
381 edges: AdjacentEdges<'g, N, E>,
384 impl<'g, N: Debug, E: Debug> Iterator for AdjacentSources<'g, N, E> {
385 type Item = NodeIndex;
387 fn next(&mut self) -> Option<NodeIndex> {
388 self.edges.next().map(|(_, edge)| edge.source)
392 pub struct DepthFirstTraversal<'g, N, E>
396 graph: &'g Graph<N, E>,
397 stack: Vec<NodeIndex>,
399 direction: Direction,
402 impl<'g, N: Debug, E: Debug> DepthFirstTraversal<'g, N, E> {
403 pub fn with_start_node(graph: &'g Graph<N, E>,
404 start_node: NodeIndex,
405 direction: Direction)
407 let mut visited = BitVector::new(graph.len_nodes());
408 visited.insert(start_node.node_id());
409 DepthFirstTraversal {
411 stack: vec![start_node],
417 fn visit(&mut self, node: NodeIndex) {
418 if self.visited.insert(node.node_id()) {
419 self.stack.push(node);
424 impl<'g, N: Debug, E: Debug> Iterator for DepthFirstTraversal<'g, N, E> {
425 type Item = NodeIndex;
427 fn next(&mut self) -> Option<NodeIndex> {
428 let next = self.stack.pop();
429 if let Some(idx) = next {
430 for (_, edge) in self.graph.adjacent_edges(idx, self.direction) {
431 let target = edge.source_or_target(self.direction);
440 pub fn source(&self) -> NodeIndex {
444 pub fn target(&self) -> NodeIndex {
448 pub fn source_or_target(&self, direction: Direction) -> NodeIndex {
449 if direction == OUTGOING {