Merge pull request #85 from whyrusleeping/feat/optimize-write-string

optimize anything using WriteString

gen.go

@@ -314,7 +314,7 @@ func emitCborMarshalStringField(w io.Writer, f Field) error {
 		}
 
 		{{ MajorType "cw" "cbg.MajTextString" (print "len(*" .Name ")") }}
-		if _, err := io.WriteString(w, string(*{{ .Name }})); err != nil {
+		if _, err := cw.WriteString(string(*{{ .Name }})); err != nil {
 			return err
 		}
 	}
@@ -324,7 +324,7 @@ func emitCborMarshalStringField(w io.Writer, f Field) error {
 	if f.Const != nil {
 		return doTemplate(w, f, `
 	{{ MajorType "cw" "cbg.MajTextString" (print "len(\""  (Deref .Const)  "\")") }}
-	if _, err := io.WriteString(w, string("{{ .Const }}")); err != nil {
+	if _, err := cw.WriteString(string("{{ .Const }}")); err != nil {
 		return err
 	}
 `)
@@ -337,7 +337,7 @@ func emitCborMarshalStringField(w io.Writer, f Field) error {
 	}
 
 	{{ MajorType "cw" "cbg.MajTextString" (print "len(" .Name ")") }}
-	if _, err := io.WriteString(w, string({{ .Name }})); err != nil {
+	if _, err := cw.WriteString(string({{ .Name }})); err != nil {
 		return err
 	}
 `)

io.go

@@ -53,16 +53,34 @@ var (
 type CborWriter struct {
 	w    io.Writer
 	hbuf []byte
+
+	sw io.StringWriter
 }
 
 func NewCborWriter(w io.Writer) *CborWriter {
 	if w, ok := w.(*CborWriter); ok {
 		return w
 	}
-	return &CborWriter{
+
+	cw := &CborWriter{
 		w:    w,
 		hbuf: make([]byte, maxHeaderSize),
 	}
+
+	if sw, ok := w.(io.StringWriter); ok {
+		cw.sw = sw
+	}
+
+	return cw
+}
+
+func (cw *CborWriter) SetWriter(w io.Writer) {
+	cw.w = w
+	if sw, ok := w.(io.StringWriter); ok {
+		cw.sw = sw
+	} else {
+		cw.sw = nil
+	}
 }
 
 func (cw *CborWriter) Write(p []byte) (n int, err error) {
@@ -78,8 +96,8 @@ func (cw *CborWriter) CborWriteHeader(t byte, l uint64) error {
 }
 
 func (cw *CborWriter) WriteString(s string) (int, error) {
-	if sw, ok := cw.w.(io.StringWriter); ok {
-		return sw.WriteString(s)
+	if cw.sw != nil {
+		return cw.sw.WriteString(s)
 	}
 	return cw.w.Write([]byte(s))
 }