pkg: a slew of examples

R=golang-dev, gri, r
CC=golang-dev
https://golang.org/cl/5676071

src/pkg/archive/zip/example_test.go

+// Copyright 2012 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 zip_test
+
+import (
+	"archive/zip"
+	"bytes"
+	"fmt"
+	"io"
+	"log"
+	"os"
+)
+
+func ExampleWriter() {
+	// Create a buffer to write our archive to.
+	buf := new(bytes.Buffer)
+
+	// Create a new zip archive.
+	w := zip.NewWriter(buf)
+
+	// Add some files to the archive.
+	var files = []struct {
+		Name, Body string
+	}{
+		{"readme.txt", "This archive contains some text files."},
+		{"gopher.txt", "Gopher names:\nGeorge\nGeoffrey\nGonzo"},
+		{"todo.txt", "Get animal handling licence.\nWrite more examples."},
+	}
+	for _, file := range files {
+		f, err := w.Create(file.Name)
+		if err != nil {
+			log.Fatal(err)
+		}
+		_, err = f.Write([]byte(file.Body))
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+
+	// Make sure to check the error on Close.
+	err := w.Close()
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExampleReader() {
+	// Open a zip archive for reading.
+	r, err := zip.OpenReader("testdata/readme.zip")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer r.Close()
+
+	// Iterate through the files in the archive,
+	// printing some of their contents.
+	for _, f := range r.File {
+		fmt.Printf("Contents of %s:\n", f.Name)
+		rc, err := f.Open()
+		if err != nil {
+			log.Fatal(err)
+		}
+		_, err = io.CopyN(os.Stdout, rc, 68)
+		if err != nil {
+			log.Fatal(err)
+		}
+		rc.Close()
+		fmt.Println()
+	}
+	// Output:
+	// Contents of README:
+	// This is the source code repository for the Go programming language.
+}

src/pkg/crypto/md5/md5_test.go

@@ -2,9 +2,10 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package md5
+package md5_test
 
 import (
+	"crypto/md5"
 	"fmt"
 	"io"
 	"testing"
@@ -52,7 +53,7 @@ var golden = []md5Test{
 func TestGolden(t *testing.T) {
 	for i := 0; i < len(golden); i++ {
 		g := golden[i]
-		c := New()
+		c := md5.New()
 		for j := 0; j < 3; j++ {
 			if j < 2 {
 				io.WriteString(c, g.in)
@@ -69,3 +70,11 @@ func TestGolden(t *testing.T) {
 		}
 	}
 }
+
+func ExampleNew() {
+	h := md5.New()
+	io.WriteString(h, "The fog is getting thicker!")
+	io.WriteString(h, "And Leon's getting laaarger!")
+	fmt.Printf("%x", h.Sum(nil))
+	// Output: e2c569be17396eca2a2e3c11578123ed
+}

src/pkg/crypto/sha1/sha1_test.go

@@ -4,9 +4,10 @@
 
 // SHA1 hash algorithm.  See RFC 3174.
 
-package sha1
+package sha1_test
 
 import (
+	"crypto/sha1"
 	"fmt"
 	"io"
 	"testing"
@@ -54,7 +55,7 @@ var golden = []sha1Test{
 func TestGolden(t *testing.T) {
 	for i := 0; i < len(golden); i++ {
 		g := golden[i]
-		c := New()
+		c := sha1.New()
 		for j := 0; j < 3; j++ {
 			if j < 2 {
 				io.WriteString(c, g.in)
@@ -71,3 +72,10 @@ func TestGolden(t *testing.T) {
 		}
 	}
 }
+
+func ExampleNew() {
+	h := sha1.New()
+	io.WriteString(h, "His money is twice tainted: 'taint yours and 'taint mine.")
+	fmt.Printf("% x", h.Sum(nil))
+	// Output: 59 7f 6a 54 00 10 f9 4c 15 d7 18 06 a9 9a 2c 87 10 e7 47 bd
+}

src/pkg/encoding/json/example_test.go

@@ -7,7 +7,10 @@ package json_test
 import (
 	"encoding/json"
 	"fmt"
+	"io"
+	"log"
 	"os"
+	"strings"
 )
 
 func ExampleMarshal() {
@@ -48,3 +51,33 @@ func ExampleUnmarshal() {
 	// Output:
 	// [{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]
 }
+
+// This example uses a Decoder to decode a stream of distinct JSON values.
+func ExampleDecoder() {
+	const jsonStream = `
+		{"Name": "Ed", "Text": "Knock knock."}
+		{"Name": "Sam", "Text": "Who's there?"}
+		{"Name": "Ed", "Text": "Go fmt."}
+		{"Name": "Sam", "Text": "Go fmt who?"}
+		{"Name": "Ed", "Text": "Go fmt yourself!"}
+	`
+	type Message struct {
+		Name, Text string
+	}
+	dec := json.NewDecoder(strings.NewReader(jsonStream))
+	for {
+		var m Message
+		if err := dec.Decode(&m); err == io.EOF {
+			break
+		} else if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%s: %s\n", m.Name, m.Text)
+	}
+	// Output:
+	// Ed: Knock knock.
+	// Sam: Who's there?
+	// Ed: Go fmt.
+	// Sam: Go fmt who?
+	// Ed: Go fmt yourself!
+}

src/pkg/errors/errors_test.go

@@ -5,29 +5,49 @@
 package errors_test
 
 import (
-	. "errors"
+	"errors"
+	"fmt"
 	"testing"
 )
 
 func TestNewEqual(t *testing.T) {
 	// Different allocations should not be equal.
-	if New("abc") == New("abc") {
+	if errors.New("abc") == errors.New("abc") {
 		t.Errorf(`New("abc") == New("abc")`)
 	}
-	if New("abc") == New("xyz") {
+	if errors.New("abc") == errors.New("xyz") {
 		t.Errorf(`New("abc") == New("xyz")`)
 	}
 
 	// Same allocation should be equal to itself (not crash).
-	err := New("jkl")
+	err := errors.New("jkl")
 	if err != err {
 		t.Errorf(`err != err`)
 	}
 }
 
 func TestErrorMethod(t *testing.T) {
-	err := New("abc")
+	err := errors.New("abc")
 	if err.Error() != "abc" {
 		t.Errorf(`New("abc").Error() = %q, want %q`, err.Error(), "abc")
 	}
 }
+
+func ExampleNew() {
+	err := errors.New("emit macho dwarf: elf header corrupted")
+	if err != nil {
+		fmt.Print(err)
+	}
+	// Output: emit macho dwarf: elf header corrupted
+}
+
+// The fmt package's Errorf function lets us use the package's formatting
+// features to create descriptive error messages.
+func ExampleNew_errorf() {
+	const name, id = "bimmler", 17
+	err := fmt.Errorf("user %q (id %d) not found", name, id)
+	if err != nil {
+		fmt.Print(err)
+	}
+	// Output: user "bimmler" (id 17) not found
+}

src/pkg/errors/example_test.go

+// Copyright 2012 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 errors_test
+
+import (
+	"fmt"
+	"time"
+)
+
+// MyError is an error implementation that includes a time and message.
+type MyError struct {
+	When time.Time
+	What string
+}
+
+func (e MyError) Error() string {
+	return fmt.Sprintf("%v: %v", e.When, e.What)
+}
+
+func oops() error {
+	return MyError{
+		time.Date(1989, 3, 15, 22, 30, 0, 0, time.UTC),
+		"the file system has gone away",
+	}
+}
+
+func Example() {
+	if err := oops(); err != nil {
+		fmt.Println(err)
+	}
+	// Output: 1989-03-15 22:30:00 +0000 UTC: the file system has gone away
+}

src/pkg/net/example_test.go

+// Copyright 2012 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 net_test
+
+import (
+	"io"
+	"log"
+	"net"
+)
+
+func ExampleListener() {
+	// Listen on TCP port 2000 on all interfaces.
+	l, err := net.Listen("tcp", ":2000")
+	if err != nil {
+		log.Fatal(err)
+	}
+	for {
+		// Wait for a connection. 
+		conn, err := l.Accept()
+		if err != nil {
+			log.Fatal(err)
+		}
+		// Handle the connection in a new goroutine.
+		// The loop then returns to accepting, so that
+		// multiple connections may be served concurrently.
+		go func(c net.Conn) {
+			// Echo all incoming data.
+			io.Copy(c, c)
+			// Shut down the connection.
+			c.Close()
+		}(conn)
+	}
+}

src/pkg/net/url/example_test.go

+// Copyright 2012 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 url_test
+
+import (
+	"fmt"
+	"log"
+	"net/url"
+)
+
+func ExampleValues() {
+	v := url.Values{}
+	v.Set("name", "Ava")
+	v.Add("friend", "Jess")
+	v.Add("friend", "Sarah")
+	v.Add("friend", "Zoe")
+	// v.Encode() == "name=Ava&friend=Jess&friend=Sarah&friend=Zoe"
+	fmt.Println(v.Get("name"))
+	fmt.Println(v.Get("friend"))
+	fmt.Println(v["friend"])
+	// Output:
+	// Ava
+	// Jess
+	// [Jess Sarah Zoe]
+}
+
+func ExampleURL() {
+	u, err := url.Parse("http://bing.com/search?q=dotnet")
+	if err != nil {
+		log.Fatal(err)
+	}
+	u.Scheme = "https"
+	u.Host = "google.com"
+	q := u.Query()
+	q.Set("q", "golang")
+	u.RawQuery = q.Encode()
+	fmt.Println(u)
+	// Output: https://google.com/search?q=golang
+}

src/pkg/sync/example_test.go

+// Copyright 2012 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 sync_test
+
+import (
+	"net/http"
+	"sync"
+)
+
+// This example fetches several URLs concurrently,
+// using a WaitGroup to block until all the fetches are complete.
+func ExampleWaitGroup() {
+	var wg sync.WaitGroup
+	var urls = []string{
+		"http://www.golang.org/",
+		"http://www.google.com/",
+		"http://www.somestupidname.com/",
+	}
+	for _, url := range urls {
+		// Increment the WaitGroup counter.
+		wg.Add(1)
+		// Launch a goroutine to fetch the URL.
+		go func(url string) {
+			// Fetch the URL.
+			http.Get(url)
+			// Decrement the counter.
+			wg.Done()
+		}(url)
+	}
+	// Wait for all HTTP fetches to complete.
+	wg.Wait()
+}