Merge pull request #18 from arran4/optimize-performCaseFirst-12956515176561281531

⚡ Optimize performCaseFirst using strings.Builder

Author: arran4

perform_case_first_bench_test.go

@@ -0,0 +1,22 @@
+package strings2
+
+import (
+	"testing"
+	"unicode"
+)
+
+func BenchmarkPerformCaseFirst(b *testing.B) {
+	s := "test"
+	fn := unicode.ToUpper
+	for i := 0; i < b.N; i++ {
+		performCaseFirst(s, fn)
+	}
+}
+
+func BenchmarkPerformCaseFirst_Long(b *testing.B) {
+	s := "teststringwithmorecharacters"
+	fn := unicode.ToUpper
+	for i := 0; i < b.N; i++ {
+		performCaseFirst(s, fn)
+	}
+}

types.go

@@ -53,7 +53,11 @@ func performCaseFirst(s string, fn func(rune) rune) (string, rune, bool) {
 	if r == u {
 		return s, 0, true
 	}
-	return string(u) + s[size:], 0, true
+	var b strings.Builder
+	b.Grow(len(s) + utf8.UTFMax)
+	b.WriteRune(u)
+	b.WriteString(s[size:])
+	return b.String(), 0, true
 }
 
 // UpperCaseFirst uppercases the first character of the string.