tlio.RingWriter

Author: nikandfor

tlio/writers.go

@@ -34,17 +34,21 @@ type (
 
 	TailWriter struct {
 		io.Writer
-		n int
-
-		i   int
-		buf [][]byte
+		RingWriter
 	}
 
 	HeadWriter struct {
 		io.Writer
 		N int
 	}
 
+	RingWriter struct {
+		n int
+
+		i   int
+		buf [][]byte
+	}
+
 	// CountingIODiscard discards data but counts writes and bytes.
 	// It's safe to use simultaneously (atomic operations are used).
 	CountingIODiscard struct {
@@ -288,13 +292,38 @@ func (w *DeLabels) Unwrap() interface{} {
 
 func NewTailWriter(w io.Writer, n int) *TailWriter {
 	return &TailWriter{
-		Writer: w,
-		n:      n,
-		buf:    make([][]byte, n),
+		Writer:     w,
+		RingWriter: RingWriter{},
 	}
 }
 
-func (w *TailWriter) Write(p []byte) (n int, err error) {
+func (w *TailWriter) Flush() (err error) {
+	_, err = w.RingWriter.WriteTo(w.Writer)
+	if err != nil {
+		return err
+	}
+
+	w.RingWriter.Reset()
+
+	if f, ok := w.Writer.(Flusher); ok {
+		return f.Flush()
+	}
+
+	return nil
+}
+
+func (w *TailWriter) Unwrap() interface{} {
+	return w.Writer
+}
+
+func NewRingWriter(n int) *RingWriter {
+	return &RingWriter{
+		n:   n,
+		buf: make([][]byte, n),
+	}
+}
+
+func (w *RingWriter) Write(p []byte) (n int, err error) {
 	i := w.i % w.n
 	w.buf[i] = append(w.buf[i][:0], p...)
 
@@ -303,31 +332,28 @@ func (w *TailWriter) Write(p []byte) (n int, err error) {
 	return len(p), nil
 }
 
-func (w *TailWriter) Flush() (err error) {
+func (w *RingWriter) WriteTo(wr io.Writer) (n int64, err error) {
 	for i := w.i; i < w.i+w.n; i++ {
 		b := w.buf[i%w.n]
 
 		if len(b) == 0 {
 			continue
 		}
 
-		_, err = w.Writer.Write(b)
+		m, err := wr.Write(b)
+		n += int64(m)
 		if err != nil {
-			return err
+			return n, err
 		}
-
-		w.buf[i%w.n] = b[:0]
-	}
-
-	if f, ok := w.Writer.(Flusher); ok {
-		return f.Flush()
 	}
 
-	return nil
+	return n, nil
 }
 
-func (w *TailWriter) Unwrap() interface{} {
-	return w.Writer
+func (w *RingWriter) Reset() {
+	for i := range w.buf {
+		w.buf[i] = w.buf[i][:0]
+	}
 }
 
 func NewHeadWriter(w io.Writer, n int) *HeadWriter {