1 files changed, 60 insertions, 0 deletions
diff --git a/vendor/regex-automata/src/sparse_set.rs b/vendor/regex-automata/src/sparse_set.rs
new file mode 100644
index 000000000..56743b033
--- /dev/null
+++ b/vendor/regex-automata/src/sparse_set.rs
@@ -0,0 +1,60 @@
+use std::slice;
+
+/// A sparse set used for representing ordered NFA states.
+///
+/// This supports constant time addition and membership testing. Clearing an
+/// entire set can also be done in constant time. Iteration yields elements
+/// in the order in which they were inserted.
+///
+/// The data structure is based on: https://research.swtch.com/sparse
+/// Note though that we don't actually use uninitialized memory. We generally
+/// reuse sparse sets, so the initial allocation cost is bareable. However, its
+/// other properties listed above are extremely useful.
+#[derive(Clone, Debug)]
+pub struct SparseSet {
+    /// Dense contains the instruction pointers in the order in which they
+    /// were inserted.
+    dense: Vec<usize>,
+    /// Sparse maps instruction pointers to their location in dense.
+    ///
+    /// An instruction pointer is in the set if and only if
+    /// sparse[ip] < dense.len() && ip == dense[sparse[ip]].
+    sparse: Box<[usize]>,
+}
+
+impl SparseSet {
+    pub fn new(size: usize) -> SparseSet {
+        SparseSet {
+            dense: Vec::with_capacity(size),
+            sparse: vec![0; size].into_boxed_slice(),
+        }
+    }
+
+    pub fn len(&self) -> usize {
+        self.dense.len()
+    }
+
+    pub fn insert(&mut self, value: usize) {
+        let i = self.len();
+        assert!(i < self.dense.capacity());
+        self.dense.push(value);
+        self.sparse[value] = i;
+    }
+
+    pub fn contains(&self, value: usize) -> bool {
+        let i = self.sparse[value];
+        self.dense.get(i) == Some(&value)
+    }
+
+    pub fn clear(&mut self) {
+        self.dense.clear();
+    }
+}
+
+impl<'a> IntoIterator for &'a SparseSet {
+    type Item = &'a usize;
+    type IntoIter = slice::Iter<'a, usize>;
+    fn into_iter(self) -> Self::IntoIter {
+        self.dense.iter()
+    }
+}