holey-bytes/hblang/src/lexer.rs
2024-05-12 20:10:50 +02:00

260 lines
6.7 KiB
Rust

#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub struct Token {
pub kind: TokenKind,
pub start: u32,
pub end: u32,
}
impl Token {
pub fn range(&self) -> std::ops::Range<usize> {
self.start as usize..self.end as usize
}
pub fn len(&self) -> u32 {
self.end - self.start
}
}
macro_rules! gen_token_kind {
($(
#[$atts:meta])*
$vis:vis enum $name:ident {
#[patterns] $(
$pattern:ident,
)*
#[keywords] $(
$keyword:ident = $keyword_lit:literal,
)*
#[punkt] $(
$punkt:ident = $punkt_lit:literal,
)*
#[ops] $(
#[prec = $prec:literal] $(
$op:ident = $op_lit:literal,
)*
)*
}
) => {
impl std::fmt::Display for $name {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
let s = match *self {
$( Self::$pattern => concat!('<', stringify!($pattern), '>'), )*
$( Self::$keyword => stringify!($keyword_lit), )*
$( Self::$punkt => stringify!($punkt_lit), )*
$($( Self::$op => $op_lit, )*)*
};
f.write_str(s)
}
}
impl $name {
#[inline(always)]
pub fn precedence(&self) -> Option<u8> {
Some(match self {
$($(Self::$op)|* => $prec,)*
_ => return None,
})
}
#[inline(always)]
fn from_ident(ident: &[u8]) -> Self {
match ident {
$($keyword_lit => Self::$keyword,)*
_ => Self::Ident,
}
}
}
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
$vis enum $name {
$( $pattern, )*
$( $keyword, )*
$( $punkt, )*
$($( $op, )*)*
}
};
}
gen_token_kind! {
pub enum TokenKind {
#[patterns]
Ident,
Number,
Eof,
Error,
#[keywords]
Return = b"return",
If = b"if",
Else = b"else",
Loop = b"loop",
Break = b"break",
Continue = b"continue",
Fn = b"fn",
Struct = b"struct",
True = b"true",
#[punkt]
LParen = "(",
RParen = ")",
LBrace = "{",
RBrace = "}",
Semi = ";",
Colon = ":",
Comma = ",",
Dot = ".",
Ctor = ".{",
#[ops]
#[prec = 1]
Decl = ":=",
Assign = "=",
#[prec = 21]
Le = "<=",
Eq = "==",
#[prec = 22]
Amp = "&",
#[prec = 23]
Plus = "+",
Minus = "-",
#[prec = 24]
Star = "*",
FSlash = "/",
}
}
pub struct Lexer<'a> {
pos: u32,
bytes: &'a [u8],
}
impl<'a> Lexer<'a> {
pub fn new(input: &'a str) -> Self {
Self {
pos: 0,
bytes: input.as_bytes(),
}
}
pub fn slice(&self, tok: std::ops::Range<usize>) -> &'a str {
unsafe { std::str::from_utf8_unchecked(&self.bytes[tok]) }
}
fn peek(&self) -> Option<u8> {
self.bytes.get(self.pos as usize).copied()
}
fn advance(&mut self) -> Option<u8> {
let c = self.peek()?;
self.pos += 1;
Some(c)
}
pub fn next(&mut self) -> Token {
Iterator::next(self).unwrap_or(Token {
kind: TokenKind::Eof,
start: self.pos,
end: self.pos,
})
}
fn advance_if(&mut self, arg: u8) -> bool {
if self.peek() == Some(arg) {
self.advance();
true
} else {
false
}
}
pub fn line_col(&self, mut start: u32) -> (usize, usize) {
self.bytes
.split(|&b| b == b'\n')
.enumerate()
.find_map(|(i, line)| {
if start < line.len() as u32 {
return Some((i + 1, start as usize + 1));
}
start -= line.len() as u32 + 1;
None
})
.unwrap_or((1, 1))
}
}
impl<'a> Iterator for Lexer<'a> {
type Item = Token;
fn next(&mut self) -> Option<Self::Item> {
use TokenKind as T;
loop {
let start = self.pos;
let kind = match self.advance()? {
b'\n' | b'\r' | b'\t' | b' ' => continue,
b'0'..=b'9' => {
while let Some(b'0'..=b'9') = self.peek() {
self.advance();
}
T::Number
}
b'a'..=b'z' | b'A'..=b'Z' | b'_' => {
while let Some(b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' | b'_') = self.peek() {
self.advance();
}
let ident = &self.bytes[start as usize..self.pos as usize];
T::from_ident(ident)
}
b':' if self.advance_if(b'=') => T::Decl,
b':' => T::Colon,
b',' => T::Comma,
b'.' if self.advance_if(b'{') => T::Ctor,
b'.' => T::Dot,
b';' => T::Semi,
b'=' if self.advance_if(b'=') => T::Eq,
b'=' => T::Assign,
b'<' if self.advance_if(b'=') => T::Le,
b'+' => T::Plus,
b'-' => T::Minus,
b'*' => T::Star,
b'/' => T::FSlash,
b'&' => T::Amp,
b'(' => T::LParen,
b')' => T::RParen,
b'{' => T::LBrace,
b'}' => T::RBrace,
_ => T::Error,
};
return Some(Token {
kind,
start,
end: self.pos,
});
}
}
}
#[cfg(test)]
mod tests {
fn lex(input: &'static str, output: &mut String) {
use {
super::{Lexer, TokenKind as T},
std::fmt::Write,
};
let mut lexer = Lexer::new(input);
loop {
let token = lexer.next();
writeln!(output, "{:?} {:?}", token.kind, &input[token.range()],).unwrap();
if token.kind == T::Eof {
break;
}
}
}
crate::run_tests! { lex:
empty => "";
whitespace => " \t\n\r";
example => include_str!("../examples/main_fn.hb");
arithmetic => include_str!("../examples/arithmetic.hb");
}
}