Avoid string copies.

ahocorasick.go

@@ -116,7 +116,7 @@ func (ac AhoCorasick) PatternCount() int {
 
 // Iter gives an iterator over the built patterns
 func (ac AhoCorasick) Iter(haystack string) Iter {
-	return ac.IterByte([]byte(haystack))
+	return ac.IterByte(unsafeBytes(haystack))
 }
 
 // IterByte gives an iterator over the built patterns
@@ -140,7 +140,7 @@ func (ac AhoCorasick) IterByte(haystack []byte) Iter {
 
 // Iter gives an iterator over the built patterns with overlapping matches
 func (ac AhoCorasick) IterOverlapping(haystack string) Iter {
-	return ac.IterOverlappingByte([]byte(haystack))
+	return ac.IterOverlappingByte(unsafeBytes(haystack))
 }
 
 // IterOverlappingByte gives an iterator over the built patterns with overlapping matches
@@ -293,7 +293,7 @@ func NewAhoCorasickBuilder(o Opts) AhoCorasickBuilder {
 func (a *AhoCorasickBuilder) Build(patterns []string) AhoCorasick {
 	bytePatterns := make([][]byte, len(patterns))
 	for pati, pat := range patterns {
-		bytePatterns[pati] = []byte(pat)
+		bytePatterns[pati] = unsafeBytes(pat)
 	}
 
 	return a.BuildByte(bytePatterns)

unsafe.go

@@ -0,0 +1,12 @@
+package aho_corasick
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+func unsafeBytes(s string) []byte {
+	str := (*reflect.StringHeader)(unsafe.Pointer(&s))
+	slice := reflect.SliceHeader{Data: str.Data, Len: str.Len, Cap: str.Len}
+	return *(*[]byte)(unsafe.Pointer(&slice))
+}