concurrency chapter

concurrency/concurrency.go

@@ -0,0 +1,28 @@
+package concurrency
+
+type (
+	WebsiteChecker func(string) bool
+
+	result struct {
+		string
+		bool
+	}
+)
+
+func CheckWebsites(wc WebsiteChecker, urls []string) map[string]bool {
+	results := make(map[string]bool)
+	resultChannel := make(chan result)
+
+	for _, url := range urls {
+		go func(u string) {
+			resultChannel <- result{u, wc(u)}
+		}(url)
+	}
+
+	for i := 0; i < len(urls); i++ {
+		r := <-resultChannel
+		results[r.string] = r.bool
+	}
+
+	return results
+}

concurrency/concurrency_test.go

@@ -0,0 +1,51 @@
+package concurrency
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+func slowStubWebsiteChecker(_ string) bool {
+	time.Sleep(20 * time.Millisecond)
+	return true
+}
+
+func BenchmarkCheckWebsites(b *testing.B) {
+	urls := make([]string, 100)
+	for i := 0; i < len(urls); i++ {
+		urls[i] = "url"
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		CheckWebsites(slowStubWebsiteChecker, urls)
+	}
+}
+
+func mockWebsiteChecker(url string) bool {
+	if url == "waat://furhurterme.geds" {
+		return false
+	}
+	return true
+}
+
+func TestCheckWebsites(t *testing.T) {
+	websites := []string{
+		"http://google.com",
+		"http://blog.gypsydave5.com",
+		"waat://furhurterme.geds",
+	}
+
+	want := map[string]bool{
+		"http://google.com":          true,
+		"http://blog.gypsydave5.com": true,
+		"waat://furhurterme.geds":    false,
+	}
+
+	got := CheckWebsites(mockWebsiteChecker, websites)
+
+	if !reflect.DeepEqual(want, got) {
+		t.Fatalf("wanted %v, got %v", want, got)
+	}
+}