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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,148 @@ | ||
| #![allow(dead_code)] | ||
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| use std::str::Chars; | ||
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| pub(super) const EOF_CHAR: char = '\0'; | ||
|
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| /// A cursor represents a pointer in the source code. | ||
| /// | ||
| /// Based on [`rustc`'s `Cursor`](https://github.com/rust-lang/rust/blob/d1b7355d3d7b4ead564dbecb1d240fcc74fff21b/compiler/rustc_lexer/src/cursor.rs) | ||
| #[derive(Clone, Debug)] | ||
| pub(super) struct Cursor<'src> { | ||
| /// An iterator over the [`char`]'s of the source code. | ||
| chars: Chars<'src>, | ||
|
|
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| /// Stores the previous character for debug assertions. | ||
| #[cfg(debug_assertions)] | ||
| prev_char: char, | ||
| } | ||
|
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| impl<'src> Cursor<'src> { | ||
| pub(super) fn new(source: &'src str) -> Self { | ||
| Self { | ||
| chars: source.chars(), | ||
| #[cfg(debug_assertions)] | ||
| prev_char: EOF_CHAR, | ||
| } | ||
| } | ||
|
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| /// Returns the previous character. Useful for debug assertions. | ||
| #[cfg(debug_assertions)] | ||
| pub(super) const fn previous(&self) -> char { | ||
| self.prev_char | ||
| } | ||
|
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| /// Peeks the next character from the input stream without consuming it. | ||
| /// Returns [`EOF_CHAR`] if the position is past the end of the file. | ||
| pub(super) fn first(&self) -> char { | ||
| self.chars.clone().next().unwrap_or(EOF_CHAR) | ||
| } | ||
|
|
||
| /// Peeks the second character from the input stream without consuming it. | ||
| /// Returns [`EOF_CHAR`] if the position is past the end of the file. | ||
| pub(super) fn second(&self) -> char { | ||
| let mut chars = self.chars.clone(); | ||
| chars.next(); | ||
| chars.next().unwrap_or(EOF_CHAR) | ||
| } | ||
|
|
||
| /// Returns the remaining text to lex. | ||
| /// | ||
| /// Use [`Cursor::text_len`] to get the length of the remaining text. | ||
| pub(super) fn rest(&self) -> &'src str { | ||
| self.chars.as_str() | ||
| } | ||
|
|
||
| /// Returns `true` if the cursor is at the end of file. | ||
| pub(super) fn is_eof(&self) -> bool { | ||
| self.chars.as_str().is_empty() | ||
| } | ||
|
|
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| /// Moves the cursor to the next character, returning the previous character. | ||
| /// Returns [`None`] if there is no next character. | ||
| pub(super) fn bump(&mut self) -> Option<char> { | ||
| let prev = self.chars.next()?; | ||
|
|
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| #[cfg(debug_assertions)] | ||
| { | ||
| self.prev_char = prev; | ||
| } | ||
|
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| Some(prev) | ||
| } | ||
|
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| pub(super) fn eat_char(&mut self, c: char) -> bool { | ||
| if self.first() == c { | ||
| self.bump(); | ||
| true | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
|
|
||
| pub(super) fn eat_char2(&mut self, c1: char, c2: char) -> bool { | ||
| let mut chars = self.chars.clone(); | ||
| if chars.next() == Some(c1) && chars.next() == Some(c2) { | ||
| self.bump(); | ||
| self.bump(); | ||
| true | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
|
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||
| pub(super) fn eat_char3(&mut self, c1: char, c2: char, c3: char) -> bool { | ||
| let mut chars = self.chars.clone(); | ||
| if chars.next() == Some(c1) && chars.next() == Some(c2) && chars.next() == Some(c3) { | ||
| self.bump(); | ||
| self.bump(); | ||
| self.bump(); | ||
| true | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
|
|
||
| pub(super) fn eat_if<F>(&mut self, mut predicate: F) -> Option<char> | ||
| where | ||
| F: FnMut(char) -> bool, | ||
| { | ||
| if predicate(self.first()) && !self.is_eof() { | ||
| self.bump() | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
|
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||
| /// Eats symbols while predicate returns true or until the end of file is reached. | ||
| #[inline] | ||
| pub(super) fn eat_while(&mut self, mut predicate: impl FnMut(char) -> bool) { | ||
| // It was tried making optimized version of this for eg. line comments, but | ||
| // LLVM can inline all of this and compile it down to fast iteration over bytes. | ||
| while predicate(self.first()) && !self.is_eof() { | ||
| self.bump(); | ||
| } | ||
| } | ||
|
|
||
| /// Skips the next `count` bytes. | ||
| /// | ||
| /// ## Panics | ||
| /// - If `count` is larger than the remaining bytes in the input stream. | ||
| /// - If `count` indexes into a multi-byte character. | ||
| pub(super) fn skip_bytes(&mut self, count: usize) { | ||
| #[cfg(debug_assertions)] | ||
| { | ||
| self.prev_char = self.chars.as_str()[..count] | ||
| .chars() | ||
| .next_back() | ||
| .unwrap_or('\0'); | ||
| } | ||
|
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| self.chars = self.chars.as_str()[count..].chars(); | ||
| } | ||
|
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| /// Skips to the end of the input stream. | ||
| pub(super) fn skip_to_end(&mut self) { | ||
| self.chars = "".chars(); | ||
| } | ||
| } |
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