Struct regex_automata::nfa::thompson::backtrack::Builder

pub struct Builder {
    config: Config,
    thompson: Compiler,
}

A builder for a bounded backtracker.

This builder permits configuring options for the syntax of a pattern, the NFA construction and the BoundedBacktracker construction. This builder is different from a general purpose regex builder in that it permits fine grain configuration of the construction process. The trade off for this is complexity, and the possibility of setting a configuration that might not make sense. For example, there are two different UTF-8 modes:

• syntax::Config::utf8 controls whether the pattern itself can contain sub-expressions that match invalid UTF-8.
• thompson::Config::utf8 controls how the regex iterators themselves advance the starting position of the next search when a match with zero length is found.

Generally speaking, callers will want to either enable all of these or disable all of these.

Example

This example shows how to disable UTF-8 mode in the syntax and the regex itself. This is generally what you want for matching on arbitrary bytes.

use regex_automata::{
    nfa::thompson::{self, backtrack::BoundedBacktracker},
    util::syntax,
    Match,
};

let re = BoundedBacktracker::builder()
    .syntax(syntax::Config::new().utf8(false))
    .thompson(thompson::Config::new().utf8(false))
    .build(r"foo(?-u:[^b])ar.*")?;
let mut cache = re.create_cache();

let haystack = b"\xFEfoo\xFFarzz\xE2\x98\xFF\n";
let expected = Some(Ok(Match::must(0, 1..9)));
let got = re.try_find_iter(&mut cache, haystack).next();
assert_eq!(expected, got);
// Notice that `(?-u:[^b])` matches invalid UTF-8,
// but the subsequent `.*` does not! Disabling UTF-8
// on the syntax permits this.
//
// N.B. This example does not show the impact of
// disabling UTF-8 mode on a BoundedBacktracker Config, since that
// only impacts regexes that can produce matches of
// length 0.
assert_eq!(b"foo\xFFarzz", &haystack[got.unwrap()?.range()]);

Fields

config: Config

thompson: Compiler

Implementations

impl Builder

pub fn new() -> Builder

Create a new BoundedBacktracker builder with its default configuration.

pub fn build(&self, pattern: &str) -> Result<BoundedBacktracker, BuildError>

Build a BoundedBacktracker from the given pattern.

If there was a problem parsing or compiling the pattern, then an error is returned.

pub fn build_many<P: AsRef<str>>( &self, patterns: &[P], ) -> Result<BoundedBacktracker, BuildError>

Build a BoundedBacktracker from the given patterns.

pub fn build_from_nfa(&self, nfa: NFA) -> Result<BoundedBacktracker, BuildError>

Build a BoundedBacktracker directly from its NFA.

Note that when using this method, any configuration that applies to the construction of the NFA itself will of course be ignored, since the NFA given here is already built.

pub fn configure(&mut self, config: Config) -> &mut Builder

Apply the given BoundedBacktracker configuration options to this builder.

pub fn syntax(&mut self, config: Config) -> &mut Builder

Set the syntax configuration for this builder using syntax::Config.

This permits setting things like case insensitivity, Unicode and multi line mode.

These settings only apply when constructing a BoundedBacktracker directly from a pattern.

pub fn thompson(&mut self, config: Config) -> &mut Builder

Set the Thompson NFA configuration for this builder using nfa::thompson::Config.

This permits setting things like if additional time should be spent shrinking the size of the NFA.

These settings only apply when constructing a BoundedBacktracker directly from a pattern.

Trait Implementations

impl Clone for Builder

fn clone(&self) -> Builder

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Builder

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.