Update http code

Author: tmpbook

.gitignore

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+*.test
+*.cpu
+*.svg

http/test_http_v1/README.md

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+## Fix the race
+
+If your code has data races, all bets are off and you're just waiting for a crash. The runtime promises nothing if you have a data race.
+
+Multiple options:
+
+- use channels
+- use a Mutex
+- use atomic
+
+### Mutex
+
+```go
+var visitors struct {
+    sync.Mutex
+    n int
+}
+...
+func foo() {
+    ...
+    visitors.Lock()
+    visitors.n++
+    yourVisitorNumber := visitors.n
+    visitors.Unlock()
+```
+[used here](./demo_test.go#L11-L14)
+
+### Atomic
+
+```go
+var visitors int64 // must be accessed atomically
+...
+func foo() {
+    ...
+    visitNum := atomic.AddInt64(&visitors, 1)
+```

http/test_http_v1/demo.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"regexp"
+	"sync"
+)
+
+var visitors struct {
+	sync.Mutex
+	n int
+}
+
+func handleHi(w http.ResponseWriter, r *http.Request) {
+	if match, _ := regexp.MatchString(`^\w*$`, r.FormValue("color")); !match {
+		http.Error(w, "Optional color is invalid", http.StatusBadRequest)
+		return
+	}
+	visitors.Lock()
+	visitors.n++
+	yourVisitorNumber := visitors.n
+	visitors.Unlock()
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	w.Write([]byte("<h1 style='color: " + r.FormValue("color") +
+		"'>Welcome!</h1>You are visitor number " + fmt.Sprint(yourVisitorNumber) + "!"))
+}
+
+func main() {
+	log.Printf("Starting on port 8080")
+	http.HandleFunc("/hi", handleHi)
+	log.Fatal(http.ListenAndServe("127.0.0.1:8080", nil))
+}

http/test_http_v1/demo_test.go

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+package main
+
+import (
+	"bufio"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+)
+
+func TestHandleRoot_Recorder(t *testing.T) {
+	rw := httptest.NewRecorder()
+	handleHi(rw, req(t, "GET / HTTP/1.0\r\n\r\n"))
+	if !strings.Contains(rw.Body.String(), "visitor number") {
+		t.Errorf("Unexpected output: %s", rw.Body)
+	}
+}
+
+func req(t testing.TB, v string) *http.Request {
+	req, err := http.ReadRequest(bufio.NewReader(strings.NewReader(v)))
+	if err != nil {
+		t.Fatal(err)
+	}
+	return req
+}
+
+// 用真实的 client & server 测试
+func TestHandleHi_TestServer(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(handleHi))
+	defer ts.Close()
+	res, err := http.Get(ts.URL)
+	t.Logf("URL: %s", ts.URL)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	if g, w := res.Header.Get("Content-Type"), "text/html; charset=utf-8"; g != w {
+		t.Errorf("Content-Type = %q; want %q", g, w)
+	}
+	slurp, err := ioutil.ReadAll(res.Body)
+	defer res.Body.Close()
+
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	t.Logf("Got: %s", slurp)
+}
+
+// 测试并行
+func TestHandleHi_TestServer_Parallel(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(handleHi))
+	defer ts.Close()
+	var wg sync.WaitGroup
+	for i := 0; i < 2; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			res, err := http.Get(ts.URL)
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			if g, w := res.Header.Get("Content-Type"), "text/html; charset=utf-8"; g != w {
+				t.Errorf("Content-Type = %q; want %q", g, w)
+			}
+			slurp, err := ioutil.ReadAll(res.Body)
+			defer res.Body.Close()
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			t.Logf("Got: %s", slurp)
+		}()
+	}
+	wg.Wait()
+}
+
+func BenchmarkHi(b *testing.B) {
+	b.ReportAllocs()
+	r := req(b, "GET / HTTP/1.0\r\n\r\n")
+	for i := 0; i < b.N; i++ {
+		rw := httptest.NewRecorder()
+		handleHi(rw, r)
+	}
+}