opt: avoid memory allocations when calling readv

pkg/ringbuffer/ring_buffer.go

@@ -40,6 +40,7 @@ var ErrIsEmpty = errors.New("ring-buffer is empty")
 
 // RingBuffer is a circular buffer that implement io.ReaderWriter interface.
 type RingBuffer struct {
+	bs      [][]byte
 	buf     []byte
 	size    int
 	r       int // next position to read
@@ -53,10 +54,11 @@ var EmptyRingBuffer = New(0)
 // New returns a new RingBuffer whose buffer has the given size.
 func New(size int) *RingBuffer {
 	if size == 0 {
-		return &RingBuffer{isEmpty: true}
+		return &RingBuffer{bs: make([][]byte, 2), isEmpty: true}
 	}
 	size = toolkit.CeilToPowerOfTwo(size)
 	return &RingBuffer{
+		bs:      make([][]byte, 2),
 		buf:     make([]byte, size),
 		size:    size,
 		isEmpty: true,

pkg/ringbuffer/ring_buffer_unix.go

@@ -53,7 +53,9 @@ func (rb *RingBuffer) CopyFromSocket(fd int) (n int, err error) {
 		}
 		return
 	}
-	n, err = io.Readv(fd, [][]byte{rb.buf[rb.w:], rb.buf[:rb.r]})
+	rb.bs[0] = rb.buf[rb.w:]
+	rb.bs[1] = rb.buf[:rb.r]
+	n, err = io.Readv(fd, rb.bs)
 	if n > 0 {
 		rb.w = (rb.w + n) % rb.size
 		rb.isEmpty = false