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use core::iter;
use super::{Error, Location, Spanned, SpannedValue};
pub(super) struct Lexed<I: Iterator> {
iter: iter::Peekable<I>,
}
impl<I: Iterator> Iterator for Lexed<I> {
type Item = I::Item;
fn next(&mut self) -> Option<Self::Item> {
self.iter.next()
}
}
impl<'iter, 'token: 'iter, I: Iterator<Item = Result<Token<'token>, Error>> + 'iter> Lexed<I> {
pub(super) fn peek(&mut self) -> Option<&I::Item> {
self.iter.peek()
}
pub(super) fn next_if_whitespace(&mut self) -> Option<Spanned<&'token [u8]>> {
if let Some(&Ok(Token::ComponentPart {
kind: ComponentKind::Whitespace,
value,
})) = self.peek()
{
self.next(); // consume
Some(value)
} else {
None
}
}
pub(super) fn next_if_not_whitespace(&mut self) -> Option<Spanned<&'token [u8]>> {
if let Some(&Ok(Token::ComponentPart {
kind: ComponentKind::NotWhitespace,
value,
})) = self.peek()
{
self.next();
Some(value)
} else {
None
}
}
pub(super) fn next_if_opening_bracket(&mut self) -> Option<Location> {
if let Some(&Ok(Token::Bracket {
kind: BracketKind::Opening,
location,
})) = self.peek()
{
self.next();
Some(location)
} else {
None
}
}
pub(super) fn peek_closing_bracket(&'iter mut self) -> Option<&'iter Location> {
if let Some(Ok(Token::Bracket {
kind: BracketKind::Closing,
location,
})) = self.peek()
{
Some(location)
} else {
None
}
}
pub(super) fn next_if_closing_bracket(&mut self) -> Option<Location> {
if let Some(&Ok(Token::Bracket {
kind: BracketKind::Closing,
location,
})) = self.peek()
{
self.next();
Some(location)
} else {
None
}
}
}
pub(super) enum Token<'a> {
Literal(Spanned<&'a [u8]>),
Bracket {
kind: BracketKind,
location: Location,
},
ComponentPart {
kind: ComponentKind,
value: Spanned<&'a [u8]>,
},
}
pub(super) enum BracketKind {
Opening,
Closing,
}
pub(super) enum ComponentKind {
#[allow(clippy::missing_docs_in_private_items)]
Whitespace,
#[allow(clippy::missing_docs_in_private_items)]
NotWhitespace,
}
fn attach_location<'item>(
iter: impl Iterator<Item = &'item u8>,
proc_span: proc_macro::Span,
) -> impl Iterator<Item = (&'item u8, Location)> {
let mut byte_pos = 0;
iter.map(move |byte| {
let location = Location {
byte: byte_pos,
proc_span,
};
byte_pos += 1;
(byte, location)
})
}
#[allow(clippy::unused_peekable)] // false positive
pub(super) fn lex<const VERSION: u8>(
mut input: &[u8],
proc_span: proc_macro::Span,
) -> Lexed<impl Iterator<Item = Result<Token<'_>, Error>>> {
assert!(version!(1..=2));
let mut depth: u8 = 0;
let mut iter = attach_location(input.iter(), proc_span).peekable();
let mut second_bracket_location = None;
let iter = iter::from_fn(move || {
if version!(..=1) {
if let Some(location) = second_bracket_location.take() {
return Some(Ok(Token::Bracket {
kind: BracketKind::Opening,
location,
}));
}
}
Some(Ok(match iter.next()? {
(b'\\', backslash_loc) if version!(2..) => match iter.next() {
Some((b'\\' | b'[' | b']', char_loc)) => {
let char = &input[1..2];
input = &input[2..];
if depth == 0 {
Token::Literal(char.spanned(backslash_loc.to(char_loc)))
} else {
Token::ComponentPart {
kind: ComponentKind::NotWhitespace,
value: char.spanned(backslash_loc.to(char_loc)),
}
}
}
Some((_, loc)) => {
return Some(Err(loc.error("invalid escape sequence")));
}
None => {
return Some(Err(backslash_loc.error("unexpected end of input")));
}
},
(b'[', location) if version!(..=1) => {
if let Some((_, second_location)) = iter.next_if(|&(&byte, _)| byte == b'[') {
second_bracket_location = Some(second_location);
input = &input[2..];
} else {
depth += 1;
input = &input[1..];
}
Token::Bracket {
kind: BracketKind::Opening,
location,
}
}
(b'[', location) => {
depth += 1;
input = &input[1..];
Token::Bracket {
kind: BracketKind::Opening,
location,
}
}
(b']', location) if depth > 0 => {
depth -= 1;
input = &input[1..];
Token::Bracket {
kind: BracketKind::Closing,
location,
}
}
(_, start_location) if depth == 0 => {
let mut bytes = 1;
let mut end_location = start_location;
while let Some((_, location)) =
iter.next_if(|&(&byte, _)| !((version!(2..) && byte == b'\\') || byte == b'['))
{
end_location = location;
bytes += 1;
}
let value = &input[..bytes];
input = &input[bytes..];
Token::Literal(value.spanned(start_location.to(end_location)))
}
(byte, start_location) => {
let mut bytes = 1;
let mut end_location = start_location;
let is_whitespace = byte.is_ascii_whitespace();
while let Some((_, location)) = iter.next_if(|&(byte, _)| {
!matches!(byte, b'\\' | b'[' | b']')
&& is_whitespace == byte.is_ascii_whitespace()
}) {
end_location = location;
bytes += 1;
}
let value = &input[..bytes];
input = &input[bytes..];
Token::ComponentPart {
kind: if is_whitespace {
ComponentKind::Whitespace
} else {
ComponentKind::NotWhitespace
},
value: value.spanned(start_location.to(end_location)),
}
}
}))
});
Lexed {
iter: iter.peekable(),
}
}