1 files changed, 344 insertions, 0 deletions
diff --git a/src/regex/mod.rs b/src/regex/mod.rs
new file mode 100644
index 0000000..be3026f
--- /dev/null
+++ b/src/regex/mod.rs
@@ -0,0 +1,344 @@
+use crate::parse::Parse;
+
+pub mod bc;
+mod byte_range;
+pub mod dfa;
+pub mod enfa;
+pub mod simple;
+
+#[derive(PartialEq, Eq, Debug, Clone, Copy, Hash)]
+pub enum LookDirection {
+    Ahead,
+    Behind,
+}
+
+impl LookDirection {
+    pub fn reverse(self) -> Self {
+        match self {
+            Self::Ahead => Self::Behind,
+            Self::Behind => Self::Ahead,
+        }
+    }
+}
+
+#[derive(PartialEq, Eq, Debug, Clone, Copy, Hash)]
+pub enum LookPolarity {
+    Positive,
+    Negative,
+}
+
+#[derive(PartialEq, Eq, Debug, Clone, Copy, Hash)]
+pub enum CharacterClass {
+    Everything,
+    Nothing,
+    Whitespace,
+    Alphabetic,
+    Alphanumeric,
+}
+
+impl CharacterClass {
+    pub fn matches(self, byte: u8) -> bool {
+        match self {
+            CharacterClass::Everything => true,
+            CharacterClass::Nothing => false,
+            CharacterClass::Whitespace => byte.is_ascii_whitespace(),
+            CharacterClass::Alphabetic => byte.is_ascii_alphabetic(),
+            CharacterClass::Alphanumeric => byte.is_ascii_alphanumeric(),
+        }
+    }
+}
+
+#[derive(PartialEq, Eq, Hash, Debug, Clone)]
+pub enum Pattern {
+    Byte(u8),
+    Range(u8, u8),
+    CharacterClass(CharacterClass),
+    Alt(Vec<Pattern>),
+    Concat(Vec<Pattern>),
+    Rep(Box<Pattern>, u32, Option<u32>, GreedyBehavior),
+    Assertion(LookDirection, LookPolarity, Box<Pattern>),
+    Submatch(Box<Pattern>),
+    Nothing,
+}
+
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+pub enum ByteConsumption {
+    Bounded(usize),
+    Unbounded,
+}
+
+impl ByteConsumption {
+    pub fn zero() -> Self {
+        Self::Bounded(0)
+    }
+    pub fn one() -> Self {
+        Self::Bounded(1)
+    }
+}
+
+impl Ord for ByteConsumption {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        match (self, other) {
+            (Self::Bounded(a), Self::Bounded(b)) => a.cmp(b),
+            (Self::Bounded(_), Self::Unbounded) => std::cmp::Ordering::Less,
+            (Self::Unbounded, Self::Bounded(_)) => std::cmp::Ordering::Greater,
+            (Self::Unbounded, Self::Unbounded) => std::cmp::Ordering::Equal,
+        }
+    }
+}
+impl PartialOrd for ByteConsumption {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl std::ops::Add for ByteConsumption {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        if let Self::Bounded(a) = self
+            && let Self::Bounded(b) = rhs
+        {
+            Self::Bounded(a + b)
+        } else {
+            Self::Unbounded
+        }
+    }
+}
+
+impl std::ops::Mul<usize> for ByteConsumption {
+    type Output = Self;
+
+    fn mul(self, rhs: usize) -> Self::Output {
+        match self {
+            Self::Bounded(x) => Self::Bounded(x * rhs),
+            Self::Unbounded => Self::Unbounded,
+        }
+    }
+}
+
+impl std::iter::Sum for ByteConsumption {
+    fn sum<I: Iterator<Item = Self>>(iter: I) -> Self {
+        iter.fold(Self::zero(), |a, b| a + b)
+    }
+}
+
+impl Pattern {
+    pub fn max_byte_consumption(&self) -> ByteConsumption {
+        match self {
+            Pattern::Byte(_) => ByteConsumption::one(),
+            Pattern::Range(_, _) => ByteConsumption::one(),
+            Pattern::CharacterClass(_) => ByteConsumption::one(),
+            Pattern::Alt(patterns) => patterns
+                .iter()
+                .map(Self::max_byte_consumption)
+                .max()
+                .unwrap_or(ByteConsumption::zero()),
+            Pattern::Concat(patterns) => patterns.iter().map(Self::max_byte_consumption).sum(),
+            Pattern::Rep(pattern, _, Some(max_reps), _) => {
+                pattern.max_byte_consumption() * (*max_reps as usize)
+            }
+            Pattern::Rep(_, _, None, _) => ByteConsumption::Unbounded,
+            Pattern::Assertion(_, _, _) => ByteConsumption::zero(),
+            Pattern::Nothing => ByteConsumption::zero(),
+            Pattern::Submatch(pat) => pat.max_byte_consumption(),
+        }
+    }
+
+    pub fn reverse(self) -> Self {
+        use Pattern::*;
+        match self {
+            Byte(_) | Nothing | Range(..) | CharacterClass(_) => self,
+            Alt(patterns) => Alt(patterns.into_iter().map(Self::reverse).collect()),
+            Concat(patterns) => Concat(patterns.into_iter().map(Self::reverse).rev().collect()),
+            Rep(pattern, min, max, greedy) => Rep(Box::new(pattern.reverse()), min, max, greedy),
+            Assertion(dir, pol, pat) => Assertion(dir.reverse(), pol, Box::new(pat.reverse())),
+            Submatch(pat) => Submatch(Box::new(pat.reverse())),
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum GreedyBehavior {
+    Greedy,
+    NonGreedy,
+}
+
+pub enum CompiledPattern {
+    Dfa(dfa::DFA),
+    Bytecode(bc::BytecodeCompiledRegex),
+    Anything(simple::Anything),
+    Nothing(simple::Nothing),
+    Exact(simple::Exact),
+}
+
+impl CompiledPattern {
+    fn is_dfa(&self) -> bool {
+        matches!(self, Self::Dfa(_))
+    }
+    fn is_bytecode(&self) -> bool {
+        matches!(self, Self::Bytecode(_))
+    }
+    fn is_simple(&self) -> bool {
+        matches!(self, Self::Anything(_) | Self::Nothing(_) | Self::Exact(_))
+    }
+}
+
+#[derive(PartialEq, Eq, Debug)]
+pub struct Match {
+    pub submatches: Box<[Option<core::ops::Range<usize>>]>,
+}
+
+impl Match {
+    pub fn new_empty() -> Self {
+        Self {
+            submatches: [].into(),
+        }
+    }
+}
+
+pub trait RegexEngine: Sized {
+    type CompileError: std::fmt::Debug + Clone;
+
+    fn compile(pat: Pattern) -> Result<Self, Self::CompileError>;
+
+    fn run(&self, input: &[u8]) -> Option<Match>;
+
+    fn matches(&self, input: &[u8]) -> bool {
+        self.run(input).is_some()
+    }
+}
+
+impl RegexEngine for CompiledPattern {
+    type CompileError = bc::RegexCompilationError;
+
+    fn compile(pat: Pattern) -> Result<Self, Self::CompileError> {
+        if let Ok(c) = simple::Anything::compile(pat.clone()) {
+            Ok(Self::Anything(c))
+        } else if let Ok(c) = simple::Nothing::compile(pat.clone()) {
+            Ok(Self::Nothing(c))
+        } else if let Ok(c) = simple::Exact::compile(pat.clone()) {
+            Ok(Self::Exact(c))
+        } else if let Ok(c) = dfa::DFA::compile(pat.clone()) {
+            Ok(Self::Dfa(c))
+        } else {
+            bc::BytecodeCompiledRegex::compile(pat).map(Self::Bytecode)
+        }
+    }
+
+    fn run(&self, input: &[u8]) -> Option<Match> {
+        match self {
+            CompiledPattern::Dfa(x) => x.run(input),
+            CompiledPattern::Bytecode(x) => x.run(input),
+            CompiledPattern::Anything(x) => x.run(input),
+            CompiledPattern::Nothing(x) => x.run(input),
+            CompiledPattern::Exact(x) => x.run(input),
+        }
+    }
+}
+
+macro_rules! all_engines {
+    ($ty_name:ident, $($x:ident : $ty:ty,)*) => {
+        pub struct $ty_name {
+            $($x: Option<$ty>,)*
+        }
+        impl RegexEngine for $ty_name {
+            type CompileError = ();
+
+            fn compile(pat: Pattern) -> Result<Self, Self::CompileError> {
+                let x = Self {
+                    $($x: RegexEngine::compile(pat.clone()).ok(),)*
+                };
+                if $(x.$x.is_none())&&* {
+                    Err(())
+                } else {
+                    Ok(x)
+                }
+            }
+
+            fn run(&self, input: &[u8]) -> Option<Match> {
+                $(let $x = self.$x.as_ref().map(|x| x.run(input));)*
+                let mut result = None;
+                $(
+                    if let Some(res) = $x {
+                        if let Some(result) = result {
+                            assert_eq!(res, result, concat!("engine ", stringify!($x), " does not agree with previously run engines."));
+                        }
+                        result = Some(res)
+                    }
+                )*
+                result.unwrap()
+            }
+        }
+    }
+}
+
+all_engines!(
+    AllEngines,
+    dfa: dfa::DFA,
+    bc: bc::BytecodeCompiledRegex,
+    any: simple::Anything,
+    nothing: simple::Nothing,
+    exact: simple::Exact,
+);
+
+impl Pattern {
+    pub fn try_compile(self) -> Result<CompiledPattern, bc::RegexCompilationError> {
+        CompiledPattern::compile(self)
+    }
+}
+
+#[cfg(test)]
+macro_rules! regex_matches {
+    ($regex:literal, $match:literal, $true:literal) => {
+        assert_eq!(
+            <Pattern as crate::parse::Parse>::parse_from_bytes($regex.as_bytes())
+                .unwrap()
+                .try_compile()
+                .unwrap()
+                .matches($match.as_bytes()),
+            $true
+        )
+    };
+}
+
+#[test]
+fn foo_matches_foo() {
+    regex_matches!("foo", "foo", true);
+}
+
+#[test]
+fn dot_star_is_simple() {
+    let x = Pattern::parse_from_bytes(b".*")
+        .unwrap()
+        .try_compile()
+        .unwrap();
+    assert!(x.is_simple());
+}
+
+#[test]
+fn match_is_bytecode() {
+    let x = Pattern::parse_from_bytes(b".*(ele.*phant).*")
+        .unwrap()
+        .try_compile()
+        .unwrap();
+    assert!(x.is_bytecode());
+}
+
+#[test]
+fn simple_word_is_exact() {
+    let x = Pattern::parse_from_bytes(b"Gnu[ ]plus[ ]Linux")
+        .unwrap()
+        .try_compile()
+        .unwrap();
+    assert!(x.is_simple());
+}
+
+#[test]
+fn no_match_is_dfa() {
+    let x = Pattern::parse_from_bytes(b".*Gnu.*plus.*Linux.*")
+        .unwrap()
+        .try_compile()
+        .unwrap();
+    assert!(x.is_dfa());
+}