encoding/binary: add Write and Read examples

R=golang-dev, r, adg
CC=golang-dev
https://golang.org/cl/5495095

src/pkg/encoding/binary/example_test.go

+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package binary_test
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"math"
+)
+
+// 18 2d 44 54 fb 21 09 40
+func ExampleWrite() {
+	buf := new(bytes.Buffer)
+	var pi float64 = math.Pi
+	err := binary.Write(buf, binary.LittleEndian, pi)
+	if err != nil {
+		fmt.Println("binary.Write failed:", err)
+	}
+	fmt.Printf("% x", buf.Bytes())
+}
+
+// cafebabe
+func ExampleWrite_multi() {
+	buf := new(bytes.Buffer)
+	var data = []interface{}{
+		int8(-54),
+		uint8(254),
+		uint16(48826),
+	}
+	for _, v := range data {
+		err := binary.Write(buf, binary.LittleEndian, v)
+		if err != nil {
+			fmt.Println("binary.Write failed:", err)
+		}
+	}
+	fmt.Printf("%x", buf.Bytes())
+}
+
+// 3.141592653589793
+func ExampleRead() {
+	var pi float64
+	b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40}
+	buf := bytes.NewBuffer(b)
+	err := binary.Read(buf, binary.LittleEndian, &pi)
+	if err != nil {
+		fmt.Println("binary.Read failed:", err)
+	}
+	fmt.Print(pi)
+}