use const [N]byte array in struct instead of heap allocated make([]by…

…te) slice

one less malloc()+GC per marshal

io.go

@@ -52,7 +52,7 @@ var (
 
 type CborWriter struct {
 	w    io.Writer
-	hbuf []byte
+	hbuf [maxHeaderSize]byte
 
 	sw io.StringWriter
 }
@@ -63,8 +63,7 @@ func NewCborWriter(w io.Writer) *CborWriter {
 	}
 
 	cw := &CborWriter{
-		w:    w,
-		hbuf: make([]byte, maxHeaderSize),
+		w: w,
 	}
 
 	if sw, ok := w.(io.StringWriter); ok {
@@ -88,11 +87,11 @@ func (cw *CborWriter) Write(p []byte) (n int, err error) {
 }
 
 func (cw *CborWriter) WriteMajorTypeHeader(t byte, l uint64) error {
-	return WriteMajorTypeHeaderBuf(cw.hbuf, cw.w, t, l)
+	return WriteMajorTypeHeaderBuf(cw.hbuf[:], cw.w, t, l)
 }
 
 func (cw *CborWriter) CborWriteHeader(t byte, l uint64) error {
-	return WriteMajorTypeHeaderBuf(cw.hbuf, cw.w, t, l)
+	return WriteMajorTypeHeaderBuf(cw.hbuf[:], cw.w, t, l)
 }
 
 func (cw *CborWriter) WriteString(s string) (int, error) {