1// pest. The Elegant Parser
2// Copyright (c) 2018 Dragoș Tiselice
3//
4// Licensed under the Apache License, Version 2.0
5// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
6// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7// option. All files in the project carrying such notice may not be copied,
8// modified, or distributed except according to those terms.
9
10// This structure serves to improve performance over Token objects in two ways:
11//
12// * it is smaller than a Token, leading to both less memory use when stored in the queue but also
13// increased speed when pushing to the queue
14// * it finds its pair in O(1) time instead of O(N), since pair positions are known at parse time
15// and can easily be stored instead of recomputed
16#[derive(Debug)]
17pub enum QueueableToken<'i, R> {
18 Start {
19 /// Queue (as a vec) contains both `Start` token and `End` for the same rule.
20 /// This field is an index of corresponding `End` token in vec.
21 end_token_index: usize,
22 /// Position from which rule was tried to parse (or successfully parsed).
23 input_pos: usize,
24 },
25 End {
26 /// Queue (as a vec) contains both `Start` token and `End` for the same rule.
27 /// This filed is an index of corresponding `Start` token in vec.
28 start_token_index: usize,
29 rule: R,
30 tag: Option<&'i str>,
31 /// Position at which successfully parsed rule finished (ended).
32 input_pos: usize,
33 },
34}
35