feat: add buffered writer

go.mod

@@ -1 +1,3 @@
 module github.com/libp2p/go-buffer-pool
+
+go 1.12

pool_test.go

@@ -139,11 +139,27 @@ func BenchmarkPool(b *testing.B) {
 				i = i << 1
 			}
 			b := p.Get(i)
+			b[0] = byte(i)
 			p.Put(b)
 		}
 	})
 }
 
+func BenchmarkAlloc(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		i := 7
+		for pb.Next() {
+			if i > 1<<20 {
+				i = 7
+			} else {
+				i = i << 1
+			}
+			b := make([]byte, i)
+			b[1] = byte(i)
+		}
+	})
+}
+
 func BenchmarkPoolOverlflow(b *testing.B) {
 	var p BufferPool
 	b.RunParallel(func(pb *testing.PB) {

writer.go

@@ -0,0 +1,119 @@
+package pool
+
+import (
+	"bufio"
+	"io"
+	"sync"
+)
+
+const WriterBufferSize = 4096
+
+var bufioWriterPool = sync.Pool{
+	New: func() interface{} {
+		return bufio.NewWriterSize(nil, WriterBufferSize)
+	},
+}
+
+// Writer is a buffered writer that returns its internal buffer in a pool when
+// not in use.
+type Writer struct {
+	W    io.Writer
+	bufw *bufio.Writer
+}
+
+func (w *Writer) ensureBuffer() {
+	if w.bufw == nil {
+		w.bufw = bufioWriterPool.Get().(*bufio.Writer)
+		w.bufw.Reset(w.W)
+	}
+}
+
+// Write writes the given byte slice to the underlying connection.
+//
+// Note: Write won't return the write buffer to the pool even if it ends up
+// being empty after the write. You must call Flush() to do that.
+func (w *Writer) Write(b []byte) (int, error) {
+	if w.bufw == nil {
+		if len(b) >= WriterBufferSize {
+			return w.W.Write(b)
+		}
+		w.bufw = bufioWriterPool.Get().(*bufio.Writer)
+		w.bufw.Reset(w.W)
+	}
+	return w.bufw.Write(b)
+}
+
+// Size returns the size of the underlying buffer.
+func (w *Writer) Size() int {
+	return WriterBufferSize
+}
+
+// Available returns the amount buffer space available.
+func (w *Writer) Available() int {
+	if w.bufw != nil {
+		return w.bufw.Available()
+	}
+	return WriterBufferSize
+}
+
+// Buffered returns the amount of data buffered.
+func (w *Writer) Buffered() int {
+	if w.bufw != nil {
+		return w.bufw.Buffered()
+	}
+	return 0
+}
+
+// WriteByte writes a single byte.
+func (w *Writer) WriteByte(b byte) error {
+	w.ensureBuffer()
+	return w.bufw.WriteByte(b)
+}
+
+// WriteRune writes a single rune, returning the number of bytes written.
+func (w *Writer) WriteRune(r rune) (int, error) {
+	w.ensureBuffer()
+	return w.bufw.WriteRune(r)
+}
+
+// WriteString writes a string, returning the number of bytes written.
+func (w *Writer) WriteString(s string) (int, error) {
+	w.ensureBuffer()
+	return w.bufw.WriteString(s)
+}
+
+// Flush flushes the write buffer, if any, and returns it to the pool.
+func (w *Writer) Flush() error {
+	if w.bufw == nil {
+		return nil
+	}
+	if err := w.bufw.Flush(); err != nil {
+		return err
+	}
+	w.bufw.Reset(nil)
+	bufioWriterPool.Put(w.bufw)
+	w.bufw = nil
+	return nil
+}
+
+// Close flushes the underlying writer and closes it if it implements the
+// io.Closer interface.
+//
+// Note: Close() closes the writer even if Flush() fails to avoid leaking system
+// resources. If you want to make sure Flush() succeeds, call it first.
+func (w *Writer) Close() error {
+	var (
+		ferr, cerr error
+	)
+	ferr = w.Flush()
+
+	// always close even if flush fails.
+	if closer, ok := w.W.(io.Closer); ok {
+		cerr = closer.Close()
+	}
+
+	if ferr != nil {
+		return ferr
+	}
+	return cerr
+}

writer_test.go

@@ -0,0 +1,91 @@
+package pool
+
+import (
+	"bytes"
+	"testing"
+)
+
+func checkSize(t *testing.T, w *Writer) {
+	if w.Size()-w.Buffered() != w.Available() {
+		t.Fatalf("size (%d), buffered (%d), available (%d) mismatch", w.Size(), w.Buffered(), w.Available())
+	}
+}
+
+func TestWriter(t *testing.T) {
+	var b bytes.Buffer
+	w := Writer{W: &b}
+	n, err := w.Write([]byte("foobar"))
+	checkSize(t, &w)
+
+	if err != nil || n != 6 {
+		t.Fatalf("write failed: %d, %s", n, err)
+	}
+	if b.Len() != 0 {
+		t.Fatal("expected the buffer to be empty")
+	}
+	if w.Buffered() != 6 {
+		t.Fatalf("expected 6 bytes to be buffered, got %d", w.Buffered())
+	}
+	checkSize(t, &w)
+	if err := w.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	checkSize(t, &w)
+	if err := w.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	checkSize(t, &w)
+	if b.String() != "foobar" {
+		t.Fatal("expected to have written foobar")
+	}
+	b.Reset()
+
+	buf := make([]byte, WriterBufferSize)
+	n, err = w.Write(buf)
+	if n != WriterBufferSize || err != nil {
+		t.Fatalf("write failed: %d, %s", n, err)
+	}
+	checkSize(t, &w)
+	if b.Len() != WriterBufferSize {
+		t.Fatal("large write should have gone through directly")
+	}
+	if err := w.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	checkSize(t, &w)
+
+	b.Reset()
+	if err := w.WriteByte(1); err != nil {
+		t.Fatal(err)
+	}
+	if w.Buffered() != 1 {
+		t.Fatalf("expected 1 byte to be buffered, got %d", w.Buffered())
+	}
+	if n, err := w.WriteRune('1'); err != nil || n != 1 {
+		t.Fatal(err)
+	}
+	if w.Buffered() != 2 {
+		t.Fatalf("expected 2 bytes to be buffered, got %d", w.Buffered())
+	}
+	checkSize(t, &w)
+	if n, err := w.WriteString("foobar"); err != nil || n != 6 {
+		t.Fatal(err)
+	}
+	if w.Buffered() != 8 {
+		t.Fatalf("expected 8 bytes to be buffered, got %d", w.Buffered())
+	}
+	checkSize(t, &w)
+	if b.Len() != 0 {
+		t.Fatal("write should have been buffered")
+	}
+	n, err = w.Write(buf)
+	if n != WriterBufferSize || err != nil {
+		t.Fatalf("write failed: %d, %s", n, err)
+	}
+	if b.Len() != WriterBufferSize || b.Bytes()[0] != 1 || b.String()[1:8] != "1foobar" {
+		t.Fatalf("failed to flush properly: len:%d, prefix:%#v", b.Len(), b.Bytes()[:10])
+	}
+	if err := w.Close(); err != nil {
+		t.Fatal(err)
+	}
+}