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Refactor/lexer hex optimization ,#5108 #5109

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21 changes: 1 addition & 20 deletions core/parser/src/lexer/cursor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@

use crate::source::{ReadChar, UTF8Input};
use boa_ast::{LinearPosition, Position, PositionGroup, SourceText};
use std::io::{self, Error, ErrorKind};
use std::io::{self, Error};

/// Cursor over the source code.
#[derive(Debug)]
Expand Down Expand Up @@ -139,25 +139,6 @@ impl<R: ReadChar> Cursor<R> {
})
}

/// Fills the buffer with all bytes until the stop byte is found.
/// Returns error when reaching the end of the buffer.
///
/// Note that all bytes up until the stop byte are added to the buffer, including the byte right before.
pub(super) fn take_until(&mut self, stop: u32, buf: &mut Vec<u32>) -> io::Result<()> {
loop {
if self.next_if(stop)? {
return Ok(());
} else if let Some(c) = self.next_char()? {
buf.push(c);
} else {
return Err(Error::new(
ErrorKind::UnexpectedEof,
format!("Unexpected end of file when looking for character {stop}"),
));
}
}
}

/// Fills a mutable slice up to the ends while characters are alphabetic. Returns
/// the number of characters read, or `N+1` if the buffer was filled but there were
/// still characters after.
Expand Down
122 changes: 52 additions & 70 deletions core/parser/src/lexer/string.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -250,69 +250,63 @@ impl StringLiteral {
{
// Support \u{X..X} (Unicode CodePoint)
if cursor.next_if(0x7B /* { */)? {
// TODO: use bytes for a bit better performance (using stack)
let mut code_point_buf = Vec::with_capacity(6);
cursor.take_until(0x7D /* } */, &mut code_point_buf)?;

let mut s = String::with_capacity(code_point_buf.len());
for c in code_point_buf {
if let Some(c) = char::from_u32(c) {
s.push(c);
} else {
let mut code_point = 0u32;
let mut first_digit = true;
loop {
let pos = cursor.pos();
let Some(c) = cursor.next_char()? else {
return Err(Error::syntax(
"Unexpected end of file when looking for character }",
pos,
));
};
if c == 0x7D
/* } */
{
if first_digit {
return Err(Error::syntax(
"malformed Unicode character escape sequence",
start_pos,
));
}
break;
}

let Some(digit) = char::from_u32(c).and_then(|c| c.to_digit(16)) else {
return Err(Error::syntax(
"malformed Unicode character escape sequence",
start_pos,
));
}
}
};

let Ok(code_point) = u32::from_str_radix(&s, 16) else {
return Err(Error::syntax(
"malformed Unicode character escape sequence",
start_pos,
));
};
code_point = (code_point << 4) | digit;

// UTF16Encoding of a numeric code point value
if code_point > 0x10_FFFF {
return Err(Error::syntax(
"Unicode codepoint must not be greater than 0x10FFFF in escape sequence",
start_pos,
));
if code_point > 0x10_FFFF {
return Err(Error::syntax(
"Unicode codepoint must not be greater than 0x10FFFF in escape sequence",
start_pos,
));
}
first_digit = false;
}

Ok(code_point)
} else {
// Grammar: Hex4Digits
// Collect each character after \u e.g \uD83D will give "D83D"
let mut buffer = [0u32; 4];
buffer[0] = cursor
.next_char()?
.ok_or_else(|| Error::syntax("invalid Unicode escape sequence", start_pos))?;
buffer[1] = cursor
.next_char()?
.ok_or_else(|| Error::syntax("invalid Unicode escape sequence", start_pos))?;
buffer[2] = cursor
.next_char()?
.ok_or_else(|| Error::syntax("invalid Unicode escape sequence", start_pos))?;
buffer[3] = cursor
.next_char()?
.ok_or_else(|| Error::syntax("invalid Unicode escape sequence", start_pos))?;

let mut s = String::with_capacity(buffer.len());
for c in buffer {
if let Some(c) = char::from_u32(c) {
s.push(c);
} else {
let mut code_point = 0u32;
for _ in 0..4 {
let pos = cursor.pos();
let c = cursor
.next_char()?
.ok_or_else(|| Error::syntax("invalid Unicode escape sequence", pos))?;
let Some(digit) = char::from_u32(c).and_then(|c| c.to_digit(16)) else {
return Err(Error::syntax("invalid Unicode escape sequence", start_pos));
}
};
code_point = (code_point << 4) | digit;
}

let Ok(code_point) = u16::from_str_radix(&s, 16) else {
return Err(Error::syntax("invalid Unicode escape sequence", start_pos));
};

Ok(u32::from(code_point))
Ok(code_point)
}
}

Expand All @@ -323,34 +317,22 @@ impl StringLiteral {
where
R: ReadChar,
{
let mut buffer = [0u32; 2];
buffer[0] = cursor
.next_char()?
.ok_or_else(|| Error::syntax("invalid Hexadecimal escape sequence", start_pos))?;
buffer[1] = cursor
.next_char()?
.ok_or_else(|| Error::syntax("invalid Hexadecimal escape sequence", start_pos))?;

let mut s = String::with_capacity(buffer.len());
for c in buffer {
if let Some(c) = char::from_u32(c) {
s.push(c);
} else {
let mut code_point = 0u32;
for _ in 0..2 {
let pos = cursor.pos();
let c = cursor
.next_char()?
.ok_or_else(|| Error::syntax("invalid Hexadecimal escape sequence", pos))?;
let Some(digit) = char::from_u32(c).and_then(|c| c.to_digit(16)) else {
return Err(Error::syntax(
"invalid Hexadecimal escape sequence",
start_pos,
));
}
};
code_point = (code_point << 4) | digit;
}

let Ok(code_point) = u16::from_str_radix(&s, 16) else {
return Err(Error::syntax(
"invalid Hexadecimal escape sequence",
start_pos,
));
};

Ok(u32::from(code_point))
Ok(code_point)
}

fn take_legacy_octal_escape_sequence<R>(
Expand Down
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