initial commit

Change-Id: Iecee6de665d30e5db1587444d8112c44bb592b4e
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,202 @@
+
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diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
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+# Go example projects
+
+This repository contains a collection of Go programs and libraries that
+demonstrate the language, standard libraries, and tools.
+
+## The examples
+
+### [hello](hello/) and [stringutil](stringutil/)
+
+    go get github.com/golang/example/hello
+
+A trivial "Hello, world" program that uses a stringutil package.
+
+Command [hello](hello/) covers:
+
+* The basic form of an executable command
+* Importing packages (from the standard library and the local repository)
+* Printing strings ([fmt](//golang.org/pkg/fmt/))
+
+Library [stringutil](stringutil/) covers:
+
+* The basic form of a library
+* Conversion between string and []rune
+* Table-driven unit tests ([testing](//golang.org/pkg/testing/))
+
+### [outyet](outyet/)
+
+    go get github.com/golang/example/outyet
+
+A web server that answers the question: "Is Go 1.x out yet?"
+
+Topics covered:
+
+* Command-line flags ([flag](//golang.org/pkg/flag/))
+* Web servers ([net/http](//golang.org/pkg/net/http/))
+* HTML Templates ([html/template](//golang.org/pkg/html/template/))
+* Logging ([log](//golang.org/pkg/log/))
+* Long-running background processes
+* Synchronizing data access between goroutines ([sync](//golang.org/pkg/sync/))
+* Exporting server state for monitoring ([expvar](//golang.org/pkg/expvar/))
+* Unit and integration tests ([testing](//golang.org/pkg/testing/))
+* Dependency injection
+* Time ([time](//golang.org/pkg/time/))
+
diff --git a/hello/hello.go b/hello/hello.go
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--- /dev/null
+++ b/hello/hello.go
@@ -0,0 +1,27 @@
+/*
+Copyright 2014 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"fmt"
+
+	"github.com/golang/example/stringutil"
+)
+
+func main() {
+	fmt.Println(stringutil.Reverse("!selpmaxe oG ,olleH"))
+}
diff --git a/outyet/main.go b/outyet/main.go
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index 0000000..7d64edd
--- /dev/null
+++ b/outyet/main.go
@@ -0,0 +1,140 @@
+/*
+Copyright 2014 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// outyet is a web server that announces whether or not a particular Go version
+// has been tagged.
+package main
+
+import (
+	"expvar"
+	"flag"
+	"fmt"
+	"html/template"
+	"log"
+	"net/http"
+	"sync"
+	"time"
+)
+
+// Command-line flags.
+var (
+	httpAddr   = flag.String("http", ":8080", "Listen address")
+	pollPeriod = flag.Duration("poll", 5*time.Second, "Poll period")
+	version    = flag.String("version", "1.4", "Go version")
+)
+
+const baseChangeURL = "https://code.google.com/p/go/source/detail?r="
+
+func main() {
+	flag.Parse()
+	changeURL := fmt.Sprintf("%sgo%s", baseChangeURL, *version)
+	http.Handle("/", NewServer(*version, changeURL, *pollPeriod))
+	log.Fatal(http.ListenAndServe(*httpAddr, nil))
+}
+
+// Exported variables for monitoring the server.
+// These are exported via HTTP as a JSON object at /debug/vars.
+var (
+	hitCount       = expvar.NewInt("hitCount")
+	pollCount      = expvar.NewInt("pollCount")
+	pollError      = expvar.NewString("pollError")
+	pollErrorCount = expvar.NewInt("pollErrorCount")
+)
+
+// Server implements the outyet server.
+// It serves the user interface (it's an http.Handler)
+// and polls the remote repository for changes.
+type Server struct {
+	version string
+	url     string
+	period  time.Duration
+
+	mu  sync.RWMutex // protects the yes variable
+	yes bool
+}
+
+// NewServer returns an initialized outyet server.
+func NewServer(version, url string, period time.Duration) *Server {
+	s := &Server{version: version, url: url, period: period}
+	go s.poll()
+	return s
+}
+
+// poll polls the change URL for the specified period until the tag exists.
+// Then it sets the Server's yes field true and exits.
+func (s *Server) poll() {
+	for !isTagged(s.url) {
+		pollSleep(s.period)
+	}
+	s.mu.Lock()
+	s.yes = true
+	s.mu.Unlock()
+	pollDone()
+}
+
+// Hooks that may be overridden for integration tests.
+var (
+	pollSleep = time.Sleep
+	pollDone  = func() {}
+)
+
+// isTagged makes an HTTP HEAD request to the given URL and reports whether it
+// returned a 200 OK response.
+func isTagged(url string) bool {
+	pollCount.Add(1)
+	r, err := http.Head(url)
+	if err != nil {
+		log.Print(err)
+		pollError.Set(err.Error())
+		pollErrorCount.Add(1)
+		return false
+	}
+	return r.StatusCode == http.StatusOK
+}
+
+// ServeHTTP implements the HTTP user interface.
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	hitCount.Add(1)
+	s.mu.RLock()
+	data := struct {
+		URL     string
+		Version string
+		Yes     bool
+	}{
+		s.url,
+		s.version,
+		s.yes,
+	}
+	s.mu.RUnlock()
+	err := tmpl.Execute(w, data)
+	if err != nil {
+		log.Print(err)
+	}
+}
+
+// tmpl is the HTML template that drives the user interface.
+var tmpl = template.Must(template.New("tmpl").Parse(`
+<!DOCTYPE html><html><body><center>
+	<h2>Is Go {{.Version}} out yet?</h2>
+	<h1>
+	{{if .Yes}}
+		<a href="{{.URL}}">YES!</a>
+	{{else}}
+		No. :-(
+	{{end}}
+	</h1>
+</center></body></html>
+`))
diff --git a/outyet/main_test.go b/outyet/main_test.go
new file mode 100644
index 0000000..d21a22c
--- /dev/null
+++ b/outyet/main_test.go
@@ -0,0 +1,99 @@
+/*
+Copyright 2014 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+// statusHandler is an http.Handler that writes an empty response using itself
+// as the response status code.
+type statusHandler int
+
+func (h *statusHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(int(*h))
+}
+
+func TestIsTagged(t *testing.T) {
+	// Set up a fake "Google Code" web server reporting 404 not found.
+	status := statusHandler(http.StatusNotFound)
+	s := httptest.NewServer(&status)
+	defer s.Close()
+
+	if isTagged(s.URL) {
+		t.Fatal("isTagged == true, want false")
+	}
+
+	// Change fake server status to 200 OK and try again.
+	status = http.StatusOK
+
+	if !isTagged(s.URL) {
+		t.Fatal("isTagged == false, want true")
+	}
+}
+
+func TestIntegration(t *testing.T) {
+	status := statusHandler(http.StatusNotFound)
+	ts := httptest.NewServer(&status)
+	defer ts.Close()
+
+	// Replace the pollSleep with a closure that we can block and unblock.
+	sleep := make(chan bool)
+	pollSleep = func(time.Duration) {
+		sleep <- true
+		sleep <- true
+	}
+
+	// Replace pollDone with a closure that will tell us when the poller is
+	// exiting.
+	done := make(chan bool)
+	pollDone = func() { done <- true }
+
+	// Put things as they were when the test finishes.
+	defer func() {
+		pollSleep = time.Sleep
+		pollDone = func() {}
+	}()
+
+	s := NewServer("1.x", ts.URL, 1*time.Millisecond)
+
+	<-sleep // Wait for poll loop to start sleeping.
+
+	// Make first request to the server.
+	r, _ := http.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+	s.ServeHTTP(w, r)
+	if b := w.Body.String(); !strings.Contains(b, "No.") {
+		t.Fatalf("body = %s, want no", b)
+	}
+
+	status = http.StatusOK
+
+	<-sleep // Permit poll loop to stop sleeping.
+	<-done  // Wait for poller to see the "OK" status and exit.
+
+	// Make second request to the server.
+	w = httptest.NewRecorder()
+	s.ServeHTTP(w, r)
+	if b := w.Body.String(); !strings.Contains(b, "YES!") {
+		t.Fatalf("body = %q, want yes", b)
+	}
+}
diff --git a/stringutil/reverse.go b/stringutil/reverse.go
new file mode 100644
index 0000000..dea9f6b
--- /dev/null
+++ b/stringutil/reverse.go
@@ -0,0 +1,27 @@
+/*
+Copyright 2014 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package stringutil contains utility functions for working with strings.
+package stringutil
+
+// Reverse returns the provided string with its runes in reverse order.
+func Reverse(s string) string {
+	r := []rune(s)
+	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
+		r[i], r[j] = r[j], r[i]
+	}
+	return string(r)
+}
diff --git a/stringutil/reverse_test.go b/stringutil/reverse_test.go
new file mode 100644
index 0000000..263a420
--- /dev/null
+++ b/stringutil/reverse_test.go
@@ -0,0 +1,34 @@
+/*
+Copyright 2014 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package stringutil
+
+import "testing"
+
+func TestReverse(t *testing.T) {
+	for _, c := range struct {
+		in, want string
+	}{
+		{"Hello, world", "dlrow ,olleH"},
+		{"Hello, 世界", "界世 ,olleH"},
+		{"", ""},
+	} {
+		got := Reverse(c.in)
+		if got != want {
+			t.Errorf("Reverse(%q) == %q, want %q", c.in, got, want)
+		}
+	}
+}