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asm: Fix off by one error in source position calculation
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@Granddave
Granddave committed Jul 6, 2024
1 parent bf2b8ae commit f8fa3ab
Showing 1 changed file with 44 additions and 60 deletions.
104 changes: 44 additions & 60 deletions src/assembler/lexer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,27 +18,31 @@ pub enum LexerError {
/// Lexer is used to tokenize source code.
#[derive(Debug)]
pub struct Lexer<'a> {
// TODO: Add filename here?
/// Source code to lex
src: &'a str,
/// Index of current position in source code (points to current char)
position: usize,
/// Index of current reading position in source code (after current char)
read_position: usize,
/// Current char under examination
ch: Option<char>,
/// Index of current position in source code (points to current char)
current_src_index: usize,
/// Index of current reading position in source code (after current char)
next_src_index: usize,
/// Current line and column number in source code
current_source_position: SourcePosition,
/// Next line and column number in source code
next_source_position: SourcePosition,
}

impl<'a> Lexer<'a> {
#[tracing::instrument]
pub fn new(src: &'a str) -> Self {
let mut lexer = Self {
src,
position: 0,
read_position: 0,
ch: None,
current_src_index: 0,
next_src_index: 0,
current_source_position: SourcePosition::default(),
next_source_position: SourcePosition::default(),
};
lexer.read_char();
lexer
Expand All @@ -47,13 +51,14 @@ impl<'a> Lexer<'a> {
#[tracing::instrument]
#[inline(always)]
fn read_char(&mut self) {
self.ch = self.src.chars().nth(self.read_position);
self.position = self.read_position;
self.current_source_position.increment_column();
self.ch = self.src.chars().nth(self.next_src_index);
self.current_src_index = self.next_src_index;
self.current_source_position = self.next_source_position;
self.next_source_position.increment_column();
if self.ch == Some('\n') {
self.current_source_position.increment_line();
self.next_source_position.increment_line();
}
self.read_position += 1;
self.next_src_index += 1;
}

#[tracing::instrument]
Expand All @@ -77,66 +82,48 @@ impl<'a> Lexer<'a> {
}

#[tracing::instrument]
fn read_while_condition(&mut self, condition: fn(char) -> bool) -> (&str, SourcePositionSpan) {
let position = self.position;
let source_position = SourcePosition {
line: self.current_source_position.line,
column: self.current_source_position.column - 1,
};
fn read_while(&mut self, condition: fn(char) -> bool) -> (&str, SourcePositionSpan) {
let start_src_index = self.current_src_index;
let start_position = self.current_source_position;
while self.ch.is_some() && condition(self.ch.expect("ch should be some")) {
self.read_char();
}
(
&self.src[position..self.position],
SourcePositionSpan::new(
source_position,
SourcePosition::new(
self.current_source_position.line,
self.current_source_position.column - 1,
),
),
&self.src[start_src_index..self.current_src_index],
SourcePositionSpan::new(start_position, self.current_source_position),
)
}

#[tracing::instrument]
fn read_one_char(&mut self) -> (&str, SourcePositionSpan) {
let position = self.position;
let source_position = SourcePosition {
line: self.current_source_position.line,
column: self.current_source_position.column - 1,
};
let start_src_index = self.current_src_index;
let start_position = self.current_source_position;
if self.ch.is_some() {
self.read_char();
}
(
&self.src[position..self.position],
SourcePositionSpan::new(
source_position,
SourcePosition::new(
self.current_source_position.line,
self.current_source_position.column - 1,
),
),
&self.src[start_src_index..self.current_src_index],
SourcePositionSpan::new(start_position, self.current_source_position),
)
}
#[tracing::instrument]
fn read_string(&mut self) -> (&str, SourcePositionSpan) {
self.read_while_condition(|ch| ch.is_ascii_alphabetic() || ch.is_ascii_digit() || ch == '_')
self.read_while(|ch| ch.is_ascii_alphabetic() || ch.is_ascii_digit() || ch == '_')
}

#[tracing::instrument]
fn read_hex(&mut self) -> (&str, SourcePositionSpan) {
self.read_while_condition(|ch| ch.is_ascii_hexdigit())
self.read_while(|ch| ch.is_ascii_hexdigit())
}

#[tracing::instrument]
fn read_binary(&mut self) -> (&str, SourcePositionSpan) {
self.read_while_condition(|ch| ch == '0' || ch == '1')
self.read_while(|ch| ch == '0' || ch == '1')
}

#[tracing::instrument]
fn read_decimal(&mut self) -> (&str, SourcePositionSpan) {
self.read_while_condition(|ch| ch.is_ascii_digit())
self.read_while(|ch| ch.is_ascii_digit())
}

#[tracing::instrument]
Expand Down Expand Up @@ -207,10 +194,7 @@ impl<'a> Lexer<'a> {
}
_ => {
return Err(LexerError::UnexpectedCharacter(
SourcePosition {
line: self.current_source_position.line,
column: self.current_source_position.column - 1,
},
self.current_source_position,
ch,
));
}
Expand Down Expand Up @@ -334,8 +318,8 @@ mod tests {
token: TokenType::Eof,
literal: "".to_string(),
span: SourcePositionSpan::new(
SourcePosition::new(1, 10),
SourcePosition::new(1, 10),
SourcePosition::new(1, 9),
SourcePosition::new(1, 9),
),
},
],
Expand Down Expand Up @@ -371,8 +355,8 @@ mod tests {
token: TokenType::Eof,
literal: "".to_string(),
span: SourcePositionSpan::new(
SourcePosition::new(1, 16),
SourcePosition::new(1, 16),
SourcePosition::new(1, 15),
SourcePosition::new(1, 15),
),
},
],
Expand Down Expand Up @@ -408,8 +392,8 @@ mod tests {
token: TokenType::Eof,
literal: "".to_string(),
span: SourcePositionSpan::new(
SourcePosition::new(1, 10),
SourcePosition::new(1, 10),
SourcePosition::new(1, 9),
SourcePosition::new(1, 9),
),
},
],
Expand Down Expand Up @@ -451,8 +435,8 @@ mod tests {
token: TokenType::Eof,
literal: "".to_string(),
span: SourcePositionSpan::new(
SourcePosition::new(1, 11),
SourcePosition::new(1, 11),
SourcePosition::new(1, 10),
SourcePosition::new(1, 10),
),
},
];
Expand Down Expand Up @@ -498,8 +482,8 @@ mod tests {
token: TokenType::Eof,
literal: "".to_string(),
span: SourcePositionSpan::new(
SourcePosition::new(1, 26),
SourcePosition::new(1, 26),
SourcePosition::new(1, 25),
SourcePosition::new(1, 25),
),
},
];
Expand Down Expand Up @@ -541,8 +525,8 @@ LDA #$00 ; Another one
token: TokenType::Eof,
literal: "".to_string(),
span: SourcePositionSpan::new(
SourcePosition::new(3, 11),
SourcePosition::new(3, 11),
SourcePosition::new(3, 10),
SourcePosition::new(3, 10),
),
},
];
Expand Down Expand Up @@ -606,8 +590,8 @@ LDA #$00 ; Another one
token: TokenType::Eof,
literal: "".to_string(),
span: SourcePositionSpan::new(
SourcePosition::new(1, 13),
SourcePosition::new(1, 13),
SourcePosition::new(1, 12),
SourcePosition::new(1, 12),
),
},
];
Expand Down

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