path: root/rust/proc-macro2/parse.rs

// SPDX-License-Identifier: Apache-2.0 OR MIT

use crate::fallback::{
    self, is_ident_continue, is_ident_start, Group, Ident, LexError, Literal, Span, TokenStream,
    TokenStreamBuilder,
};
use crate::{Delimiter, Punct, Spacing, TokenTree};
use core::char;
use core::str::{Bytes, CharIndices, Chars};

#[derive(Copy, Clone, Eq, PartialEq)]
pub(crate) struct Cursor<'a> {
    pub(crate) rest: &'a str,
    #[cfg(span_locations)]
    pub(crate) off: u32,
}

impl<'a> Cursor<'a> {
    pub(crate) fn advance(&self, bytes: usize) -> Cursor<'a> {
        let (_front, rest) = self.rest.split_at(bytes);
        Cursor {
            rest,
            #[cfg(span_locations)]
            off: self.off + _front.chars().count() as u32,
        }
    }

    pub(crate) fn starts_with(&self, s: &str) -> bool {
        self.rest.starts_with(s)
    }

    pub(crate) fn starts_with_char(&self, ch: char) -> bool {
        self.rest.starts_with(ch)
    }

    pub(crate) fn starts_with_fn<Pattern>(&self, f: Pattern) -> bool
    where
        Pattern: FnMut(char) -> bool,
    {
        self.rest.starts_with(f)
    }

    pub(crate) fn is_empty(&self) -> bool {
        self.rest.is_empty()
    }

    fn len(&self) -> usize {
        self.rest.len()
    }

    fn as_bytes(&self) -> &'a [u8] {
        self.rest.as_bytes()
    }

    fn bytes(&self) -> Bytes<'a> {
        self.rest.bytes()
    }

    fn chars(&self) -> Chars<'a> {
        self.rest.chars()
    }

    fn char_indices(&self) -> CharIndices<'a> {
        self.rest.char_indices()
    }

    fn parse(&self, tag: &str) -> Result<Cursor<'a>, Reject> {
        if self.starts_with(tag) {
            Ok(self.advance(tag.len()))
        } else {
            Err(Reject)
        }
    }
}

pub(crate) struct Reject;
type PResult<'a, O> = Result<(Cursor<'a>, O), Reject>;

fn skip_whitespace(input: Cursor) -> Cursor {
    let mut s = input;

    while !s.is_empty() {
        let byte = s.as_bytes()[0];
        if byte == b'/' {
            if s.starts_with("//")
                && (!s.starts_with("///") || s.starts_with("////"))
                && !s.starts_with("//!")
            {
                let (cursor, _) = take_until_newline_or_eof(s);
                s = cursor;
                continue;
            } else if s.starts_with("/**/") {
                s = s.advance(4);
                continue;
            } else if s.starts_with("/*")
                && (!s.starts_with("/**") || s.starts_with("/***"))
                && !s.starts_with("/*!")
            {
                match block_comment(s) {
                    Ok((rest, _)) => {
                        s = rest;
                        continue;
                    }
                    Err(Reject) => return