perf(thrift): WriteStringNocopy one less func call (#32)

goos: darwin
goarch: arm64
pkg: github.com/cloudwego/gopkg/protocol/thrift
                                 │  ./old.txt  │             ./new.txt              │
                                 │   sec/op    │   sec/op     vs base               │
WriteString/WriteStringNoCopy-12   4.336n ± 1%   2.374n ± 0%  -45.25% (p=0.002 n=6)

.gitignore

@@ -31,3 +31,8 @@ output/*
 # Go workspace file
 go.work
 go.work.sum
+
+
+# benchmark comparision
+old.txt
+new.txt

protocol/thrift/binary.go

@@ -132,7 +132,12 @@ func (BinaryProtocol) WriteString(buf []byte, v string) int {
 }
 
 func (p BinaryProtocol) WriteStringNocopy(buf []byte, w NocopyWriter, v string) int {
-	return p.WriteBinaryNocopy(buf, w, hack.StringToByteSlice(v))
+	if w == nil || len(v) < nocopyWriteThreshold {
+		return p.WriteString(buf, v)
+	}
+	binary.BigEndian.PutUint32(buf, uint32(len(v)))
+	_ = w.WriteDirect(hack.StringToByteSlice(v), len(buf[4:])) // always err == nil ?
+	return 4
 }
 
 // Append methods

protocol/thrift/binary_test.go

@@ -428,6 +428,7 @@ func TestNocopyWrite(t *testing.T) {
 	expectb := make([]byte, 0, 2*x.StringLength(smallstr)+x.StringLength(largestr))
 	expectb = x.AppendString(expectb, smallstr)
 	expectb = x.AppendString(expectb, largestr)
+	expectb = x.AppendString(expectb, largestr)
 	expectb = x.AppendString(expectb, smallstr)
 
 	// generate testing data
@@ -436,8 +437,26 @@ func TestNocopyWrite(t *testing.T) {
 	b := w.Malloc(len(expectb))
 	i += x.WriteStringNocopy(b[i:], w, smallstr)
 	i += x.WriteStringNocopy(b[i:], w, largestr)
+	i += x.WriteBinaryNocopy(b[i:], w, []byte(largestr))
 	i += x.WriteStringNocopy(b[i:], w, smallstr)
-	require.Equal(t, len(expectb)-len(largestr), i) // without len(largestr)
-	require.Equal(t, 1, w.WriteDirectN())
+	require.Equal(t, len(expectb)-i, 2*len(largestr)) // without 2*len(largestr)
+	require.Equal(t, 2, w.WriteDirectN())
 	require.Equal(t, expectb, w.Bytes())
 }
+
+func BenchmarkWriteString(b *testing.B) {
+	smallstr := "helloworld"
+	buf := make([]byte, 4+len(smallstr))
+	x := BinaryProtocol{}
+
+	b.Run("WriteString", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			x.WriteString(buf, smallstr)
+		}
+	})
+	b.Run("WriteStringNoCopy", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			x.WriteStringNocopy(buf, nil, smallstr)
+		}
+	})
+}