lib/fs: Optimize TempName + some cosmetic changes (#7911)

lib/fs/tempname_test.go

@@ -7,20 +7,31 @@
 package fs
 
 import (
+	"path/filepath"
 	"strings"
 	"testing"
 )
 
 func TestLongTempFilename(t *testing.T) {
-	filename := ""
-	for i := 0; i < 300; i++ {
-		filename += "l"
-	}
+	filename := strings.Repeat("l", 300)
 	tFile := TempName(filename)
-	if len(tFile) < 10 || len(tFile) > 200 {
+	if len(tFile) < 10 || len(tFile) > 160 {
 		t.Fatal("Invalid long filename")
 	}
 	if !strings.HasSuffix(TempName("short"), "short.tmp") {
 		t.Fatal("Invalid short filename", TempName("short"))
 	}
 }
+
+func benchmarkTempName(b *testing.B, filename string) {
+	filename = filepath.Join("/Users/marieantoinette", filename)
+
+	b.ReportAllocs()
+
+	for i := 0; i < b.N; i++ {
+		TempName(filename)
+	}
+}
+
+func BenchmarkTempNameShort(b *testing.B) { benchmarkTempName(b, "somefile.txt") }
+func BenchmarkTempNameLong(b *testing.B)  { benchmarkTempName(b, strings.Repeat("a", 270)) }