1use std::str::Chars;
2
3pub enum FrontmatterAllowed {
4 Yes,
5 No,
6}
7
8pub struct Cursor<'a> {
13 len_remaining: usize,
14 chars: Chars<'a>,
16 pub(crate) frontmatter_allowed: FrontmatterAllowed,
17 #[cfg(debug_assertions)]
18 prev: char,
19}
20
21pub(crate) const EOF_CHAR: char = '\0';
22
23impl<'a> Cursor<'a> {
24 pub fn new(input: &'a str, frontmatter_allowed: FrontmatterAllowed) -> Cursor<'a> {
25 Cursor {
26 len_remaining: input.len(),
27 chars: input.chars(),
28 frontmatter_allowed,
29 #[cfg(debug_assertions)]
30 prev: EOF_CHAR,
31 }
32 }
33
34 pub fn as_str(&self) -> &'a str {
35 self.chars.as_str()
36 }
37
38 pub(crate) fn prev(&self) -> char {
41 #[cfg(debug_assertions)]
42 {
43 self.prev
44 }
45
46 #[cfg(not(debug_assertions))]
47 {
48 EOF_CHAR
49 }
50 }
51
52 pub fn first(&self) -> char {
57 self.chars.clone().next().unwrap_or(EOF_CHAR)
59 }
60
61 pub(crate) fn second(&self) -> char {
63 let mut iter = self.chars.clone();
65 iter.next();
66 iter.next().unwrap_or(EOF_CHAR)
67 }
68
69 pub fn third(&self) -> char {
71 let mut iter = self.chars.clone();
73 iter.next();
74 iter.next();
75 iter.next().unwrap_or(EOF_CHAR)
76 }
77
78 pub(crate) fn is_eof(&self) -> bool {
80 self.chars.as_str().is_empty()
81 }
82
83 pub(crate) fn pos_within_token(&self) -> u32 {
85 (self.len_remaining - self.chars.as_str().len()) as u32
86 }
87
88 pub(crate) fn reset_pos_within_token(&mut self) {
90 self.len_remaining = self.chars.as_str().len();
91 }
92
93 pub(crate) fn bump(&mut self) -> Option<char> {
95 let c = self.chars.next()?;
96
97 #[cfg(debug_assertions)]
98 {
99 self.prev = c;
100 }
101
102 Some(c)
103 }
104
105 pub(crate) fn bump_bytes(&mut self, n: usize) {
107 self.chars = self.as_str()[n..].chars();
108 }
109
110 pub(crate) fn eat_while(&mut self, mut predicate: impl FnMut(char) -> bool) {
112 while predicate(self.first()) && !self.is_eof() {
115 self.bump();
116 }
117 }
118
119 pub(crate) fn eat_until(&mut self, byte: u8) {
120 self.chars = match memchr::memchr(byte, self.as_str().as_bytes()) {
121 Some(index) => self.as_str()[index..].chars(),
122 None => "".chars(),
123 }
124 }
125}