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-rw-r--r--crates/ra_syntax/src/parsing/lexer/ptr.rs162
1 files changed, 162 insertions, 0 deletions
diff --git a/crates/ra_syntax/src/parsing/lexer/ptr.rs b/crates/ra_syntax/src/parsing/lexer/ptr.rs
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1use crate::TextUnit;
2
3use std::str::Chars;
4
5/// A simple view into the characters of a string.
6pub(crate) struct Ptr<'s> {
7 text: &'s str,
8 len: TextUnit,
9}
10
11impl<'s> Ptr<'s> {
12 /// Creates a new `Ptr` from a string.
13 pub fn new(text: &'s str) -> Ptr<'s> {
14 Ptr { text, len: 0.into() }
15 }
16
17 /// Gets the length of the remaining string.
18 pub fn into_len(self) -> TextUnit {
19 self.len
20 }
21
22 /// Gets the current character, if one exists.
23 pub fn current(&self) -> Option<char> {
24 self.chars().next()
25 }
26
27 /// Gets the nth character from the current.
28 /// For example, 0 will return the current character, 1 will return the next, etc.
29 pub fn nth(&self, n: u32) -> Option<char> {
30 self.chars().nth(n as usize)
31 }
32
33 /// Checks whether the current character is `c`.
34 pub fn at(&self, c: char) -> bool {
35 self.current() == Some(c)
36 }
37
38 /// Checks whether the next characters match `s`.
39 pub fn at_str(&self, s: &str) -> bool {
40 let chars = self.chars();
41 chars.as_str().starts_with(s)
42 }
43
44 /// Checks whether the current character satisfies the predicate `p`.
45 pub fn at_p<P: Fn(char) -> bool>(&self, p: P) -> bool {
46 self.current().map(p) == Some(true)
47 }
48
49 /// Checks whether the nth character satisfies the predicate `p`.
50 pub fn nth_is_p<P: Fn(char) -> bool>(&self, n: u32, p: P) -> bool {
51 self.nth(n).map(p) == Some(true)
52 }
53
54 /// Moves to the next character.
55 pub fn bump(&mut self) -> Option<char> {
56 let ch = self.chars().next()?;
57 self.len += TextUnit::of_char(ch);
58 Some(ch)
59 }
60
61 /// Moves to the next character as long as `pred` is satisfied.
62 pub fn bump_while<F: Fn(char) -> bool>(&mut self, pred: F) {
63 loop {
64 match self.current() {
65 Some(c) if pred(c) => {
66 self.bump();
67 }
68 _ => return,
69 }
70 }
71 }
72
73 /// Returns the text up to the current point.
74 pub fn current_token_text(&self) -> &str {
75 let len: u32 = self.len.into();
76 &self.text[..len as usize]
77 }
78
79 /// Returns an iterator over the remaining characters.
80 fn chars(&self) -> Chars {
81 let len: u32 = self.len.into();
82 self.text[len as usize..].chars()
83 }
84}
85
86#[cfg(test)]
87mod tests {
88 use super::*;
89
90 #[test]
91 fn test_current() {
92 let ptr = Ptr::new("test");
93 assert_eq!(ptr.current(), Some('t'));
94 }
95
96 #[test]
97 fn test_nth() {
98 let ptr = Ptr::new("test");
99 assert_eq!(ptr.nth(0), Some('t'));
100 assert_eq!(ptr.nth(1), Some('e'));
101 assert_eq!(ptr.nth(2), Some('s'));
102 assert_eq!(ptr.nth(3), Some('t'));
103 assert_eq!(ptr.nth(4), None);
104 }
105
106 #[test]
107 fn test_at() {
108 let ptr = Ptr::new("test");
109 assert!(ptr.at('t'));
110 assert!(!ptr.at('a'));
111 }
112
113 #[test]
114 fn test_at_str() {
115 let ptr = Ptr::new("test");
116 assert!(ptr.at_str("t"));
117 assert!(ptr.at_str("te"));
118 assert!(ptr.at_str("test"));
119 assert!(!ptr.at_str("tests"));
120 assert!(!ptr.at_str("rust"));
121 }
122
123 #[test]
124 fn test_at_p() {
125 let ptr = Ptr::new("test");
126 assert!(ptr.at_p(|c| c == 't'));
127 assert!(!ptr.at_p(|c| c == 'e'));
128 }
129
130 #[test]
131 fn test_nth_is_p() {
132 let ptr = Ptr::new("test");
133 assert!(ptr.nth_is_p(0, |c| c == 't'));
134 assert!(!ptr.nth_is_p(1, |c| c == 't'));
135 assert!(ptr.nth_is_p(3, |c| c == 't'));
136 assert!(!ptr.nth_is_p(150, |c| c == 't'));
137 }
138
139 #[test]
140 fn test_bump() {
141 let mut ptr = Ptr::new("test");
142 assert_eq!(ptr.current(), Some('t'));
143 ptr.bump();
144 assert_eq!(ptr.current(), Some('e'));
145 ptr.bump();
146 assert_eq!(ptr.current(), Some('s'));
147 ptr.bump();
148 assert_eq!(ptr.current(), Some('t'));
149 ptr.bump();
150 assert_eq!(ptr.current(), None);
151 ptr.bump();
152 assert_eq!(ptr.current(), None);
153 }
154
155 #[test]
156 fn test_bump_while() {
157 let mut ptr = Ptr::new("test");
158 assert_eq!(ptr.current(), Some('t'));
159 ptr.bump_while(|c| c != 's');
160 assert_eq!(ptr.current(), Some('s'));
161 }
162}