Add example about ReadFrom + bufio interaction

Fixes #125

Author: eikenb

example_test.go

@@ -1,7 +1,9 @@
 package sftp_test
 
 import (
+	"bufio"
 	"fmt"
+	"io"
 	"log"
 	"os"
 	"os/exec"
@@ -107,13 +109,13 @@ func ExampleClient_Mkdir_parents() {
 	sshFxFailure := uint32(4)
 	mkdirParents := func(client *sftp.Client, dir string) (err error) {
 		var parents string
-		
+
 		if path.IsAbs(dir) {
 			// Otherwise, an absolute path given below would be turned in to a relative one
 			// by splitting on "/"
 			parents = "/"
 		}
-		
+
 		for _, name := range strings.Split(dir, "/") {
 			if name == "" {
 				// Paths with double-/ in them should just move along
@@ -145,3 +147,18 @@ func ExampleClient_Mkdir_parents() {
 		log.Fatal(err)
 	}
 }
+
+func ExampleFile_ReadFrom_bufio() {
+	// Using Bufio to buffer writes going to an sftp.File won't buffer as it
+	// skips buffering if the underlying writer support ReadFrom. The
+	// workaround is to wrap your writer in a struct that only implements
+	// io.Writer.
+	//
+	// For background see github.com/pkg/sftp/issues/125
+
+	var data_source io.Reader
+	var f *sftp.File
+	type writerOnly struct{ io.Writer }
+	bw := bufio.NewWriter(writerOnly{f}) // no ReadFrom()
+	bw.ReadFrom(data_source)
+}