Enum WhichCaptures

pub enum WhichCaptures {
    All,
    Implicit,
    None,
}

A configuration indicating which kinds of State::Capture states to include.

This configuration can be used with Config::which_captures to control which capture states are compiled into a Thompson NFA.

The default configuration is WhichCaptures::All.

Variants

All

All capture states, including those corresponding to both implicit and explicit capture groups, are included in the Thompson NFA.

Implicit

Only capture states corresponding to implicit capture groups are included. Implicit capture groups appear in every pattern implicitly and correspond to the overall match of a pattern.

This is useful when one only cares about the overall match of a pattern. By excluding capture states from explicit capture groups, one might be able to reduce the memory usage of a multi-pattern regex substantially if it was otherwise written to have many explicit capture groups.

None

No capture states are compiled into the Thompson NFA.

This is useful when capture states are either not needed (for example, if one is only trying to build a DFA) or if they aren’t supported (for example, a reverse NFA).

Warning

Callers must be exceedingly careful when using this option. In particular, not all regex engines support reporting match spans when using this option (for example, PikeVM or BoundedBacktracker).

Perhaps more confusingly, using this option with such an engine means that an is_match routine could report true when find reports None. This is generally not something that should happen, but the low level control provided by this crate makes it possible.

Similarly, any regex engines (like meta::Regex) should always return None from find routines when this option is used, even if some of its internal engines could find the match boundaries. This is because inputs from user data could influence engine selection, and thus influence whether a match is found or not. Indeed, meta::Regex::find will always return None when configured with this option.

Implementations

impl WhichCaptures

pub fn is_none(&self) -> bool

Returns true if this configuration indicates that no capture states should be produced in an NFA.

pub fn is_any(&self) -> bool

Returns true if this configuration indicates that some capture states should be added to an NFA. Note that this might only include capture states for implicit capture groups.

Trait Implementations

impl Clone for WhichCaptures

fn clone(&self) -> WhichCaptures

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for WhichCaptures

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

Formats the value using the given formatter.

impl Default for WhichCaptures

fn default() -> WhichCaptures

Returns the “default value” for a type.

impl Copy for WhichCaptures