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|
use super::{Parse, ParseError, Result};
mod byte_range;
mod dfa;
mod enfa;
#[derive(PartialEq, Debug, Clone)]
pub enum Pattern {
Byte(u8),
Range(u8, u8),
Alt(Vec<Pattern>),
Concat(Vec<Pattern>),
Rep(Box<Pattern>, u32, Option<u32>),
Nothing,
}
impl Parse for Pattern {
fn parse(b: &mut super::Cursor<'_>) -> super::Result<Self> {
parse_alt(b)
}
}
fn parse_alt(s: &mut super::Cursor<'_>) -> Result<Pattern> {
let mut seqs = vec![];
loop {
let seq = parse_seq(s)?;
if seq != Pattern::Nothing {
seqs.push(seq);
}
if s.has() && s.peek() == b'|' {
s.adv();
} else {
break;
}
}
Ok(match seqs.len() {
0 => Pattern::Nothing,
1 => seqs.into_iter().next().unwrap(),
_ => Pattern::Alt(seqs),
})
}
fn parse_seq(s: &mut super::Cursor<'_>) -> Result<Pattern> {
let mut reps = vec![];
loop {
let rep = parse_rep(s)?;
if rep != Pattern::Nothing {
reps.push(rep);
} else {
break;
}
}
Ok(match reps.len() {
0 => Pattern::Nothing,
1 => reps.into_iter().next().unwrap(),
_ => Pattern::Concat(reps),
})
}
fn parse_rep(s: &mut super::Cursor<'_>) -> Result<Pattern> {
let atom = parse_atom(s)?;
if atom == Pattern::Nothing {
return Ok(atom);
}
if !s.has() {
return Ok(atom);
}
match s.peek() {
b'*' => {
s.adv();
Ok(Pattern::Rep(Box::new(atom), 0, None))
}
b'+' => {
s.adv();
Ok(Pattern::Rep(Box::new(atom), 1, None))
}
b'?' => {
s.adv();
Ok(Pattern::Rep(Box::new(atom), 0, Some(1)))
}
_ => Ok(atom),
}
// TODO: non-greedy
}
const SYMBOLS: &[u8] = b"{}[]()*+-?| ";
fn is_symbol(x: u8) -> bool {
SYMBOLS.contains(&x)
}
fn parse_atom(s: &mut super::Cursor<'_>) -> Result<Pattern> {
if !s.has() {
return Ok(Pattern::Nothing);
}
match s.peek() {
b'[' => {
s.adv();
let mut ranges = Vec::new();
loop {
if !s.has() {
return Err(ParseError::Eof);
}
let tok = s.adv();
if tok == b']' {
if ranges.is_empty() {
todo!("error handling for empty alternative list");
}
return Ok(Pattern::Alt(ranges));
}
if is_symbol(tok) {
return Err(ParseError::Unknown(tok));
}
if s.has() && s.peek() == b'-' {
s.adv();
if !s.has() {
return Err(ParseError::Eof);
}
let tok2 = s.adv();
if is_symbol(tok2) {
return Err(ParseError::Unknown(tok2));
}
ranges.push(Pattern::Range(tok, tok2));
} else {
ranges.push(Pattern::Byte(tok));
}
}
}
b'(' => {
s.adv();
let inner = Pattern::parse(s)?;
if !s.has() {
return Err(ParseError::Eof);
}
if s.adv() != b')' {
return Err(ParseError::Expected(')'));
}
Ok(inner)
}
x if is_symbol(x) => Ok(Pattern::Nothing),
ch => {
s.adv();
Ok(Pattern::Byte(ch))
}
}
}
pub struct CompiledPattern {
dfa: dfa::DFA,
}
impl std::fmt::Debug for CompiledPattern {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
self.dfa.fmt(f)
}
}
impl Pattern {
pub fn compile(self) -> CompiledPattern {
let enfa = enfa::ENFA::from(self);
let dfa = dfa::DFA::from(enfa);
CompiledPattern { dfa }
}
}
impl CompiledPattern {
pub fn matches(&self, bytes: &[u8]) -> bool {
self.dfa.matches(bytes)
}
}
#[cfg(test)]
macro_rules! regex_matches {
($regex:literal, $match:literal, $true:literal) => {
assert_eq!(
Pattern::parse_from_bytes($regex.as_bytes())
.unwrap()
.compile()
.matches($match.as_bytes()),
$true
)
};
}
#[test]
fn foo_matches_foo() {
regex_matches!("foo", "foo", true);
}
|
