codekingpro/portable-devtools

1// Copyright 2013 The Go Authors. All rights reserved.2// Use of this source code is governed by a BSD-style3// license that can be found in the LICENSE file.4 5package gob_test6 7import (8	"bytes"9	"encoding/gob"10	"fmt"11	"log"12	"math"13)14 15type Point struct {16	X, Y int17}18 19func (p Point) Hypotenuse() float64 {20	return math.Hypot(float64(p.X), float64(p.Y))21}22 23type Pythagoras interface {24	Hypotenuse() float6425}26 27// This example shows how to encode an interface value. The key28// distinction from regular types is to register the concrete type that29// implements the interface.30func Example_interface() {31	var network bytes.Buffer // Stand-in for the network.32 33	// We must register the concrete type for the encoder and decoder (which would34	// normally be on a separate machine from the encoder). On each end, this tells the35	// engine which concrete type is being sent that implements the interface.36	gob.Register(Point{})37 38	// Create an encoder and send some values.39	enc := gob.NewEncoder(&network)40	for i := 1; i <= 3; i++ {41		interfaceEncode(enc, Point{3 * i, 4 * i})42	}43 44	// Create a decoder and receive some values.45	dec := gob.NewDecoder(&network)46	for i := 1; i <= 3; i++ {47		result := interfaceDecode(dec)48		fmt.Println(result.Hypotenuse())49	}50 51	// Output:52	// 553	// 1054	// 1555}56 57// interfaceEncode encodes the interface value into the encoder.58func interfaceEncode(enc *gob.Encoder, p Pythagoras) {59	// The encode will fail unless the concrete type has been60	// registered. We registered it in the calling function.61 62	// Pass pointer to interface so Encode sees (and hence sends) a value of63	// interface type. If we passed p directly it would see the concrete type instead.64	// See the blog post, "The Laws of Reflection" for background.65	err := enc.Encode(&p)66	if err != nil {67		log.Fatal("encode:", err)68	}69}70 71// interfaceDecode decodes the next interface value from the stream and returns it.72func interfaceDecode(dec *gob.Decoder) Pythagoras {73	// The decode will fail unless the concrete type on the wire has been74	// registered. We registered it in the calling function.75	var p Pythagoras76	err := dec.Decode(&p)77	if err != nil {78		log.Fatal("decode:", err)79	}80	return p81}82