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Fix tricky subtle bugs in trie matching

This commit is contained in:
Wilson Lin 2020-07-03 22:32:16 +10:00
parent 97e02b33b7
commit 1ee193de1b
1 changed files with 7 additions and 3 deletions
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10
src/pattern.rs
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@ -2,7 +2,7 @@
pub struct TrieNode<V: 'static + Copy> {
// Using a children array of size 256 would probably be fastest, but waste too much memory and cause slow compiles
// and large binaries. Instead, we only store the children between the first and last defined (see `gen/trie.ts`).
// When getting a child, use `index + offset`.
// When getting a child, use `index - offset`.
pub offset: usize,
pub value: Option<V>,
pub children: &'static [Option<&'static TrieNode<V>>],
@ -29,7 +29,8 @@ impl<V: 'static + Copy> TrieNode<V> {
let mut node: &TrieNode<V> = self;
let mut next_pos = from;
while let Some(&c) = text.get(next_pos) {
match node.children.get(c as usize + node.offset) {
// Let it underflow for performance, it should be safe as the largest index is 256.
match node.children.get((c as usize).wrapping_sub(node.offset)) {
Some(Some(child)) => node = child,
None | Some(None) => return None,
};
@ -47,9 +48,12 @@ impl<V: 'static + Copy> TrieNode<V> {
let mut value: Option<TrieNodeMatch<V>> = None;
let mut pos = 0;
while let Some((new_node, new_pos)) = node.next_matching_node(text, pos) {
value = Some(TrieNodeMatch::Found { len: pos, value: new_node.value.unwrap() });
if new_pos == pos || new_node.value.is_none() {
break;
};
node = new_node;
pos = new_pos;
value = Some(TrieNodeMatch::Found { len: pos, value: node.value.unwrap() });
};
value.unwrap_or(TrieNodeMatch::NotFound { reached: pos })
}