Struct Matcher 

pub struct Matcher { /* private fields */ }

The scratch a match needs, kept across calls.

ARGREP runs a predicate per visited element, so the three vectors are allocated once for the command rather than once per element. A Matcher can be used with any Regex; it grows to the largest one it has seen.

Implementations

impl Matcher

pub fn new() -> Matcher

A matcher with nothing allocated yet.

pub fn reserve(&mut self, re: &Regex)

Grows the scratch to what re will need, so that matching never does.

A state is added at most once per step, so none of the four vectors can go past the program size. Doing the growth here means the caller can put every allocation ARGREP makes in the part of the command that reads the arguments, and the walk over the elements allocates nothing at all.

pub fn is_match(&mut self, re: &Regex, hay: &[u8]) -> bool

Whether re matches anywhere in hay.

Unanchored, which is what regexec without an anchor does and what ARGREP RE means: the pattern has to match some run of bytes, not the whole element.

The walk is a Thompson simulation. Every state that could be live at a position is live at once, so a byte is looked at exactly once and the cost is the subject length times the program size in the worst case, with no backtracking and therefore no pattern that makes it exponential.

Trait Implementations

impl Debug for Matcher

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

Formats the value using the given formatter.

impl Default for Matcher

fn default() -> Matcher

Returns the “default value” for a type.