blob: 6b317173f849538f9431f9a9ef9910b6d4d088f7 (
plain)
pub struct Scanner {
source: Box<[char]>,
position: usize,
}
impl Scanner {
pub fn new(source: impl AsRef<str>) -> Self {
Self {
source: source.as_ref().chars().collect(),
position: 0,
}
}
pub fn position(&self) -> usize {
self.position
}
pub fn goto(&mut self, position: usize) -> Option<String> {
// allow reverse ranges
let production = if self.position < position {
self.source.get(self.position..position)?.iter().collect()
} else {
self.source
.get(position..self.position)?
.iter()
.rev()
.collect()
};
self.position = position;
Some(production)
}
pub fn advance(&mut self, amount: usize) -> Option<String> {
self.goto(self.position + amount)
}
pub fn find_substring(&self, substring: impl AsRef<str>) -> Option<usize> {
self.source
.get(self.position..)?
.iter()
.collect::<String>()
.find(substring.as_ref())
}
pub fn starts_with(&self, substring: impl AsRef<str>) -> Option<usize> {
let mut i = self.position;
for substring_char in substring.as_ref().chars() {
if *self.source.get(i)? != substring_char {
return None;
}
i += 1;
}
Some(i)
}
pub fn advance_if_starts_with(&mut self, substring: impl AsRef<str>) -> Option<String> {
let position = self.starts_with(substring)?;
self.goto(position)
}
}
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