regexr 0.1.4

//! NFA (Nondeterministic Finite Automaton) module.
//!
//! Implements two NFA constructions:
//! - **Thompson's construction**: For PikeVM and DFA (has ε-transitions)
//! - **Glushkov construction**: For Shift-Or (ε-free, position-based)
//!
//! Also provides UTF-8 automata compilation for Unicode character classes.
//!
//! # Tagged NFA
//!
//! The `tagged` submodule provides Tagged NFA execution for patterns with:
//! - Lookaround assertions (lookahead, lookbehind)
//! - Non-greedy quantifiers
//! - Complex capture groups with liveness-optimized copying

mod glushkov;
mod state;
pub mod tagged;
mod thompson;
pub mod utf8_automata;

pub use glushkov::{
    compile_glushkov, compile_glushkov_wide, BitSet256, BitSet256Iter, ByteSet, GlushkovNfa,
    GlushkovWideNfa, MAX_POSITIONS, MAX_POSITIONS_WIDE,
};
pub use state::*;
pub use thompson::*;

use crate::error::Result;
use crate::hir::Hir;

/// Whether `pos` satisfies the `$`/`\Z` end anchor (`NfaInstruction::EndOfText`):
/// it holds at the end of the input, or immediately before a single trailing
/// newline (PCRE/Python `$` semantics, non-multiline). `\z` (strict end) is
/// compiled separately and does not use this.
#[inline]
pub fn at_end_or_before_final_newline(input: &[u8], pos: usize) -> bool {
    pos == input.len() || (pos + 1 == input.len() && input[pos] == b'\n')
}

/// Whether `pos` is a UTF-8 codepoint boundary in `input` (start of a codepoint,
/// or the end). Matches are only attempted at boundaries so a zero-width/optional
/// construct can't match in the middle of a multi-byte codepoint — the Unicode
/// semantics of PCRE/Python on valid UTF-8, which regexr targets for tokenization.
#[inline]
pub fn is_utf8_boundary(input: &[u8], pos: usize) -> bool {
    pos >= input.len() || (input[pos] & 0xC0) != 0x80
}

/// Compiles an HIR to a Thompson NFA.
pub fn compile(hir: &Hir) -> Result<Nfa> {
    let mut builder = NfaBuilder::new();
    builder.build(hir)
}