Implement io.ReaderFrom/WriterTo for Conn

This change increase performance when proxying wrapped connections using io.Copy.
Since go 1.11 copying between tcp connections uses the splice system call on linux yielding considerable performance improvments.
See: https://golang.org/doc/go1.11#net

Signed-off-by: Fabian Ruff <[email protected]>

Author: databus23

protocol.go

@@ -2,6 +2,7 @@ package proxyproto
 
 import (
 	"bufio"
+	"io"
 	"net"
 	"sync"
 	"time"
@@ -237,3 +238,21 @@ func (p *Conn) readHeader() error {
 
 	return err
 }
+
+// ReadFrom implements the io.ReaderFrom ReadFrom method
+func (p *Conn) ReadFrom(r io.Reader) (int64, error) {
+	if rf, ok := p.conn.(io.ReaderFrom); ok {
+		return rf.ReadFrom(r)
+	}
+	return io.Copy(p.conn, r)
+}
+
+// WriteTo implements io.WriterTo
+func (p *Conn) WriteTo(w io.Writer) (int64, error) {
+	var err error
+	p.once.Do(func() { p.readErr = p.readHeader() })
+	if err != nil {
+		return 0, err
+	}
+	return p.bufReader.WriteTo(w)
+}