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//! Character-level scanning for the lexer.
use crate::parser::lexing::LexError;
use super::Lexer;
impl<'a> Lexer<'a> {
pub(super) fn skip_whitespace(&mut self) {
while let Some(&ch) = self.peek_char() {
if ch == ' ' || ch == '\t' || ch == '\r' || ch == '\n' {
self.read_char();
} else {
break;
}
}
}
pub(super) fn read_identifier(&mut self) -> String {
let start = self.position;
while let Some(&ch) = self.peek_char() {
if ch.is_alphanumeric() || ch == '_' {
self.read_char();
} else {
break;
}
}
self.input
.get(start..self.position)
.unwrap_or("")
.to_string()
}
pub(super) fn read_backtick_identifier(&mut self) -> String {
let start = self.position;
loop {
match self.peek_char() {
Some(&'`') => {
self.read_char();
break;
}
Some(&ch) if ch == '\n' || ch == '\r' => {
break;
}
Some(_) => {
self.read_char();
}
None => break,
}
}
self.input
.get(start..self.position.saturating_sub(1))
.unwrap_or("")
.to_string()
}
pub(super) fn read_number(&mut self) -> String {
let start = self.position;
let mut has_decimal = false;
let mut has_exponent = false;
while let Some(&ch) = self.peek_char() {
if ch.is_ascii_digit() {
self.read_char();
} else if ch == '.' && !has_decimal && !has_exponent {
// Check whether a number follows the text (using “peek” without consuming any characters).
let mut temp_chars = self.chars.clone();
temp_chars.next(); // Skip.
if temp_chars.peek().is_some_and(|c| c.is_ascii_digit()) {
has_decimal = true;
self.read_char();
} else {
break;
}
} else if (ch == 'e' || ch == 'E') && !has_exponent {
has_exponent = true;
self.read_char();
if let Some(&ch) = self.peek_char() {
if ch == '+' || ch == '-' {
self.read_char();
}
}
} else {
break;
}
}
self.input
.get(start..self.position)
.unwrap_or("")
.to_string()
}
pub(super) fn read_string(&mut self) -> Result<String, LexError> {
let start_position = self.current_position();
let quote = match self.read_char() {
Some(ch) => ch,
None => {
return Err(LexError::new(
"Unexpected end of input while reading string".to_string(),
start_position,
));
}
};
let mut result = String::new();
loop {
match self.peek_char() {
Some(&'\\') => {
self.read_char();
if let Some(ch) = self.read_char() {
match ch {
'n' => result.push('\n'),
't' => result.push('\t'),
'r' => result.push('\r'),
'\\' => result.push('\\'),
'"' => result.push('"'),
'\'' => result.push('\''),
'`' => result.push('`'),
'0' => result.push('\0'),
'\n' => {
while let Some(&c) = self.peek_char() {
if c == ' ' || c == '\t' {
self.read_char();
} else {
break;
}
}
continue;
}
'u' => {
let mut unicode_seq = String::new();
for _ in 0..4 {
if let Some(&c) = self.peek_char() {
if c.is_ascii_hexdigit() {
unicode_seq.push(c);
self.read_char();
} else {
break;
}
} else {
break;
}
}
if !unicode_seq.is_empty() {
if let Ok(code_point) = u32::from_str_radix(&unicode_seq, 16) {
if let Some(ch) = char::from_u32(code_point) {
result.push(ch);
}
} else {
self.add_error(LexError::invalid_escape_sequence(
format!("u{}", unicode_seq),
self.current_position(),
));
}
}
}
'x' => {
let mut hex_seq = String::new();
for _ in 0..2 {
if let Some(&c) = self.peek_char() {
if c.is_ascii_hexdigit() {
hex_seq.push(c);
self.read_char();
} else {
break;
}
} else {
break;
}
}
if !hex_seq.is_empty() {
if let Ok(byte) = u8::from_str_radix(&hex_seq, 16) {
result.push(byte as char);
} else {
self.add_error(LexError::invalid_escape_sequence(
format!("x{}", hex_seq),
self.current_position(),
));
}
}
}
_ => {
result.push('\\');
result.push(ch);
}
}
}
}
Some(&'\'') | Some(&'"') => match self.peek_char() {
Some(&q) if q == quote => {
self.read_char();
return Ok(result);
}
Some(_) => {
let ch = self.read_char().ok_or_else(|| {
LexError::unexpected_end_of_input(self.current_position())
})?;
result.push(ch);
}
None => {
self.add_error(LexError::unterminated_string(start_position));
return Err(LexError::unterminated_string(start_position));
}
},
Some(&'\n') => {
self.add_error(LexError::unterminated_string(start_position));
return Err(LexError::unterminated_string(start_position));
}
Some(&ch) => {
result.push(ch);
self.read_char();
}
None => {
self.add_error(LexError::unterminated_string(start_position));
return Err(LexError::unterminated_string(start_position));
}
}
}
}
pub(super) fn skip_comment(&mut self) -> Result<(), LexError> {
let start_position = self.current_position();
match self.peek_char() {
Some(&'/') => {
// Use clone to peek ahead without consuming characters
let mut temp_chars = self.chars.clone();
temp_chars.next(); // Skip the first /
match temp_chars.peek() {
Some(&'/') => {
// Line comment: // ...
self.read_char(); // consume /
self.read_char(); // consume /
while let Some(&ch) = self.peek_char() {
if ch == '\n' {
break;
}
self.read_char();
}
Ok(())
}
Some(&'*') => {
// Block comment: /* ... */
self.read_char(); // consume /
self.read_char(); // consume *
loop {
match self.peek_char() {
Some(&'*') => {
self.read_char();
if let Some(&'/') = self.peek_char() {
self.read_char();
return Ok(());
}
}
Some(&'\n') => {
self.read_char();
return Ok(());
}
Some(_) => {
self.read_char();
}
None => {
let error = LexError::unterminated_comment(start_position);
self.add_error(error.clone());
return Err(error);
}
}
}
}
_ => {
// Not a comment (e.g., / is division operator)
Err(LexError::new(
"Not a comment".to_string(),
self.current_position(),
))
}
}
}
Some(&'-') => {
// Check whether the next character is also "-" (use the "clone" function to avoid consuming the current character).
let mut temp_chars = self.chars.clone();
temp_chars.next(); // Skip the first one.
if let Some(&'-') = temp_chars.peek() {
// These are SQL comments; they consume two "-" characters each.
self.read_char(); // Read the first one -
self.read_char(); // Read the second one...
while let Some(&ch) = self.peek_char() {
if ch == '\n' {
break;
}
self.read_char();
}
Ok(())
} else {
// Don't return errors; let the caller handle them.
Err(LexError::new(
"Not a comment".to_string(),
self.current_position(),
))
}
}
_ => Ok(()),
}
}
/// Parse vector elements after '[' in VECTOR[...] syntax
pub(super) fn parse_vector_elements(&mut self) -> Vec<f32> {
let mut elements = Vec::new();
loop {
self.skip_whitespace();
// Parse number
if let Some(&ch) = self.peek_char() {
if ch.is_ascii_digit() || ch == '-' || ch == '.' {
let number_str = self.read_number();
if let Ok(num) = number_str.parse::<f32>() {
elements.push(num);
}
}
}
self.skip_whitespace();
// Check for comma or end
if let Some(&',') = self.peek_char() {
self.read_char(); // consume comma
} else {
break;
}
}
// consume ']'
if let Some(&']') = self.peek_char() {
self.read_char();
}
elements
}
}