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Avoid allocating in lex_decimal (#7252)
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@MichaReiser
MichaReiser committed Sep 11, 2023
1 parent 0357e80 commit 7440e54
Showing 1 changed file with 71 additions and 44 deletions.
115 changes: 71 additions & 44 deletions crates/ruff_python_parser/src/lexer.rs
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Expand Up @@ -28,7 +28,6 @@
//!
//! [Lexical analysis]: https://docs.python.org/3/reference/lexical_analysis.html

use std::borrow::Cow;
use std::iter::FusedIterator;
use std::{char, cmp::Ordering, str::FromStr};

Expand Down Expand Up @@ -263,9 +262,10 @@ impl<'source> Lexer<'source> {
'x' | 'o' | 'b'
));

let value_text = self.radix_run(None, radix);
let mut number = LexedText::new(self.offset(), self.source);
self.radix_run(&mut number, radix);
let value =
BigInt::from_str_radix(&value_text, radix.as_u32()).map_err(|e| LexicalError {
BigInt::from_str_radix(number.as_str(), radix.as_u32()).map_err(|e| LexicalError {
error: LexicalErrorType::OtherError(format!("{e:?}")),
location: self.token_range().start(),
})?;
Expand All @@ -278,15 +278,14 @@ impl<'source> Lexer<'source> {
debug_assert!(self.cursor.previous().is_ascii_digit() || self.cursor.previous() == '.');
let start_is_zero = first_digit_or_dot == '0';

let mut value_text = if first_digit_or_dot == '.' {
String::new()
} else {
self.radix_run(Some(first_digit_or_dot), Radix::Decimal)
.into_owned()
let mut number = LexedText::new(self.token_start(), self.source);
if first_digit_or_dot != '.' {
number.push(first_digit_or_dot);
self.radix_run(&mut number, Radix::Decimal);
};

let is_float = if first_digit_or_dot == '.' || self.cursor.eat_char('.') {
value_text.push('.');
number.push('.');

if self.cursor.eat_char('_') {
return Err(LexicalError {
Expand All @@ -295,7 +294,7 @@ impl<'source> Lexer<'source> {
});
}

value_text.push_str(&self.radix_run(None, Radix::Decimal));
self.radix_run(&mut number, Radix::Decimal);
true
} else {
// Normal number:
Expand All @@ -304,14 +303,14 @@ impl<'source> Lexer<'source> {

let is_float = match self.cursor.rest().as_bytes() {
[b'e' | b'E', b'0'..=b'9', ..] | [b'e' | b'E', b'-' | b'+', b'0'..=b'9', ..] => {
value_text.push('e');
self.cursor.bump(); // e | E
// 'e' | 'E'
number.push(self.cursor.bump().unwrap());

if let Some(sign) = self.cursor.eat_if(|c| matches!(c, '+' | '-')) {
value_text.push(sign);
number.push(sign);
}

value_text.push_str(&self.radix_run(None, Radix::Decimal));
self.radix_run(&mut number, Radix::Decimal);

true
}
Expand All @@ -320,7 +319,7 @@ impl<'source> Lexer<'source> {

if is_float {
// Improvement: Use `Cow` instead of pushing to value text
let value = f64::from_str(&value_text).map_err(|_| LexicalError {
let value = f64::from_str(number.as_str()).map_err(|_| LexicalError {
error: LexicalErrorType::OtherError("Invalid decimal literal".to_owned()),
location: self.token_start(),
})?;
Expand All @@ -337,10 +336,10 @@ impl<'source> Lexer<'source> {
} else {
// Parse trailing 'j':
if self.cursor.eat_if(|c| matches!(c, 'j' | 'J')).is_some() {
let imag = f64::from_str(&value_text).unwrap();
let imag = f64::from_str(number.as_str()).unwrap();
Ok(Tok::Complex { real: 0.0, imag })
} else {
let value = value_text.parse::<BigInt>().unwrap();
let value = number.as_str().parse::<BigInt>().unwrap();
if start_is_zero && !value.is_zero() {
// leading zeros in decimal integer literals are not permitted
return Err(LexicalError {
Expand All @@ -356,34 +355,19 @@ impl<'source> Lexer<'source> {
/// Consume a sequence of numbers with the given radix,
/// the digits can be decorated with underscores
/// like this: '`1_2_3_4`' == '1234'
fn radix_run(&mut self, first: Option<char>, radix: Radix) -> Cow<'source, str> {
let start = if let Some(first) = first {
self.offset() - first.text_len()
} else {
self.offset()
};
self.cursor.eat_while(|c| radix.is_digit(c));

let number = &self.source[TextRange::new(start, self.offset())];

// Number that contains `_` separators. Remove them from the parsed text.
if radix.is_digit(self.cursor.second()) && self.cursor.eat_char('_') {
let mut value_text = number.to_string();

loop {
if let Some(c) = self.cursor.eat_if(|c| radix.is_digit(c)) {
value_text.push(c);
} else if self.cursor.first() == '_' && radix.is_digit(self.cursor.second()) {
// Skip over `_`
self.cursor.bump();
} else {
break;
}
fn radix_run(&mut self, number: &mut LexedText, radix: Radix) {
loop {
if let Some(c) = self.cursor.eat_if(|c| radix.is_digit(c)) {
number.push(c);
}
// Number that contains `_` separators. Remove them from the parsed text.
else if self.cursor.first() == '_' && radix.is_digit(self.cursor.second()) {
// Skip over `_`
self.cursor.bump();
number.skip_char();
} else {
break;
}

Cow::Owned(value_text)
} else {
Cow::Borrowed(number)
}
}

Expand Down Expand Up @@ -1236,6 +1220,49 @@ const fn is_python_whitespace(c: char) -> bool {
)
}

enum LexedText<'a> {
Source { source: &'a str, range: TextRange },
Owned(String),
}

impl<'a> LexedText<'a> {
fn new(start: TextSize, source: &'a str) -> Self {
Self::Source {
range: TextRange::empty(start),
source,
}
}

fn push(&mut self, c: char) {
match self {
LexedText::Source { range, source } => {
*range = range.add_end(c.text_len());
debug_assert!(source[*range].ends_with(c));
}
LexedText::Owned(owned) => owned.push(c),
}
}

fn as_str<'b>(&'b self) -> &'b str
where
'b: 'a,
{
match self {
LexedText::Source { range, source } => &source[*range],
LexedText::Owned(owned) => owned,
}
}

fn skip_char(&mut self) {
match self {
LexedText::Source { range, source } => {
*self = LexedText::Owned(source[*range].to_string());
}
LexedText::Owned(_) => {}
}
}
}

#[cfg(test)]
mod tests {
use num_bigint::BigInt;
Expand Down

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