Pool result matches

core_matcher.go

@@ -177,7 +177,7 @@ func (m *coreMatcher) matchesForFields(fields []Field, bufs *nfaBuffers) ([]X, e
 	for i := 0; i < len(fields); i++ {
 		tryToMatch(fields, i, cmFields.state, matches, bufs)
 	}
-	return matches.matches(), nil
+	return matches.matchesInto(bufs.resultBuf[:0]), nil
 }
 
 // tryToMatch tries to match the field at fields[index] to the provided state. If it does match and generate

match_set.go

@@ -46,3 +46,12 @@ func (m *matchSet) matches() []X {
 	}
 	return matches
 }
+
+// matchesInto appends matches to the provided buffer and returns it.
+// This avoids allocating a new slice for the result.
+func (m *matchSet) matchesInto(buf []X) []X {
+	for x := range m.set {
+		buf = append(buf, x)
+	}
+	return buf
+}

nfa.go

@@ -75,6 +75,7 @@ type nfaBuffers struct {
 	eClosure       *epsilonClosure
 	matches        *matchSet
 	transitionsBuf []*fieldMatcher
+	resultBuf      []X
 }
 
 func newNfaBuffers() *nfaBuffers {
@@ -84,6 +85,7 @@ func newNfaBuffers() *nfaBuffers {
 		eClosure:       newEpsilonClosure(),
 		matches:        newMatchSet(),
 		transitionsBuf: make([]*fieldMatcher, 0, 16),
+		resultBuf:      make([]X, 0, 16),
 	}
 }