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//! core lexer implementation
use crate::error::LexerError;
use crate::token::{Token, TokenKind};
use crate::keywords::{is_keyword, is_directive};
use crate::position::InputReader;
use crate::parsers::{read_identifier, read_number, skip_whitespace, skip_comment};
pub struct Lexer {
reader: InputReader,
}
impl Lexer {
pub fn new(input: &str) -> Self {
Self {
reader: InputReader::new(input),
}
}
pub fn next_token(&mut self) -> Result<Token, LexerError> {
loop {
skip_whitespace(&mut self.reader);
// check for comments
if self.reader.peek() == Some(';') ||
(self.reader.peek() == Some('/') && self.reader.peek_ahead(1) == Some('/')) {
skip_comment(&mut self.reader);
continue;
}
let start_line = self.reader.line();
let start_column = self.reader.column();
match self.reader.peek() {
None => {
return Ok(Token::new(TokenKind::Eof, String::new(), start_line, start_column));
}
Some(ch) if ch.is_alphabetic() || ch == '_' => {
let identifier = read_identifier(&mut self.reader);
// if next character is colon (label definition)
if self.reader.peek() == Some(':') {
self.reader.advance(); // consume the colon
return Ok(Token::new(
TokenKind::LabelDef,
identifier,
start_line,
start_column,
));
}
// determine token type
let kind = if is_keyword(&identifier) {
TokenKind::Keyword
} else if is_directive(&identifier) {
TokenKind::Directive
} else {
TokenKind::Identifier
};
return Ok(Token::new(kind, identifier, start_line, start_column));
}
Some(ch) if ch.is_ascii_digit() || ch == '-' => {
// negative number or just a minus sign
if ch == '-' {
if let Some(next) = self.reader.peek_ahead(1) {
if !next.is_ascii_digit() {
// just a minus punctuation
self.reader.advance();
return Ok(Token::new(
TokenKind::Punctuation,
ch.to_string(),
start_line,
start_column,
));
}
} else {
// end of input, just a minus
self.reader.advance();
return Ok(Token::new(
TokenKind::Punctuation,
ch.to_string(),
start_line,
start_column,
));
}
}
let number = read_number(&mut self.reader)?;
return Ok(Token::new(TokenKind::Number, number, start_line, start_column));
}
Some(ch) if "[]{}(),.#+-*/=<>!&|^~".contains(ch) => {
self.reader.advance();
return Ok(Token::new(
TokenKind::Punctuation,
ch.to_string(),
start_line,
start_column,
));
}
Some(ch) => {
return Err(LexerError::InvalidCharacter {
line: start_line,
column: start_column,
character: ch,
});
}
}
}
}
pub fn tokenize(&mut self) -> Result<Vec<Token>, LexerError> {
let mut tokens = Vec::new();
loop {
let token = self.next_token()?;
let is_eof = token.kind == TokenKind::Eof;
tokens.push(token);
if is_eof {
break;
}
}
Ok(tokens)
}
}