encoding/gob: add examples
Also tweak the package document, putting in section headings and
adding a sentence about intended use.
Fixes #4925.
R=golang-dev, iant, adg, ugorji
CC=golang-dev
https://golang.org/cl/14519044
diff --git a/src/pkg/encoding/gob/example_encdec_test.go b/src/pkg/encoding/gob/example_encdec_test.go
new file mode 100644
index 0000000..0ae6d9d
--- /dev/null
+++ b/src/pkg/encoding/gob/example_encdec_test.go
@@ -0,0 +1,61 @@
+// Copyright 2013 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 gob_test
+
+import (
+ "bytes"
+ "encoding/gob"
+ "fmt"
+ "log"
+)
+
+// The Vector type has unexported fields, which the package cannot access.
+// We therefore write a BinaryMarshal/BinaryUnmarshal method pair to allow us
+// to send and receive the type with the gob package. These interfaces are
+// defined in the "encoding" package.
+// We could equivalently use the locally defined GobEncode/GobDecoder
+// interfaces.
+type Vector struct {
+ x, y, z int
+}
+
+func (v Vector) MarshalBinary() ([]byte, error) {
+ // A simple encoding: plain text.
+ var b bytes.Buffer
+ fmt.Fprintln(&b, v.x, v.y, v.z)
+ return b.Bytes(), nil
+}
+
+// UnmarshalBinary modifies the receiver so it must take a pointer receiver.
+func (v *Vector) UnmarshalBinary(data []byte) error {
+ // A simple encoding: plain text.
+ b := bytes.NewBuffer(data)
+ _, err := fmt.Fscanln(b, &v.x, &v.y, &v.z)
+ return err
+}
+
+// This example transmits a value that implements the custom encoding and decoding methods.
+func Example_gob_encode_decode() {
+ var network bytes.Buffer // Stand-in for the network.
+
+ // Create an encoder and send a value.
+ enc := gob.NewEncoder(&network)
+ err := enc.Encode(Vector{3, 4, 5})
+ if err != nil {
+ log.Fatal("encode:", err)
+ }
+
+ // Create a decoder and receive a value.
+ dec := gob.NewDecoder(&network)
+ var v Vector
+ err = dec.Decode(&v)
+ if err != nil {
+ log.Fatal("decode:", err)
+ }
+ fmt.Println(v)
+
+ // Output:
+ // {3 4 5}
+}
