finish fan_in pattern

gomore/04_fan_in/fan_in.go

@@ -1,11 +1,46 @@
 package fanin
 
-func generatePipeline(numbers []int) <-chan int {
+import "sync"
+
+// Merge operate a FanIn to compose different channels into one
+func Merge(cs ...<-chan int) <-chan int {
+	var wg sync.WaitGroup
+
+	out := make(chan int, 3)
+
+	wg.Add(len(cs))
+
+	// Start an send goroutine for each input channel in cs. send
+	// copies values from c to out until c is closed, then calls wg.Done.
+	send := func(c <-chan int) {
+		for n := range c {
+			out <- n
+		}
+		wg.Done()
+	}
+
+	//启动多个 go routine 开始工作
+	for _, c := range cs {
+		go send(c)
+	}
+	// Start a goroutine to close out once all the send goroutines are
+	// done.  This must start after the wg.Add call.
+	//关闭动作,放在发送一方，会更好
+	go func() {
+		wg.Wait()
+		close(out)
+	}()
+
+	return out
+}
+
+func generateNumbersPipeline(numbers []int) <-chan int {
 	out := make(chan int)
 	go func() {
 		for _, n := range numbers {
 			out <- n
 		}
+		//发送完成之后关闭
 		close(out)
 	}()
 	return out
@@ -17,22 +52,8 @@ func squareNumber(in <-chan int) <-chan int {
 		for n := range in {
 			out <- n * n
 		}
+		//发送完成之后关闭
 		close(out)
 	}()
 	return out
 }
-
-func fanIn(input1, input2 <-chan int) <-chan int {
-	c := make(chan int)
-	go func() {
-		for {
-			select {
-			case s := <-input1:
-				c <- s
-			case s := <-input2:
-				c <- s
-			}
-		}
-	}()
-	return c
-}

gomore/04_fan_in/fan_in.md

@@ -1,41 +0,0 @@
-# Fan-In Messaging Patterns
-
-===================================
-Fan-In is a messaging pattern used to create a funnel for work amongst workers (clients: source, server: destination).
-
-We can model fan-in using the Go channels.
-
-```go
-// Merge different channels in one channel
-func Merge(cs ...<-chan int) <-chan int {
-  var wg sync.WaitGroup
-
-  out := make(chan int)
-
-  // Start an send goroutine for each input channel in cs. send
-  // copies values from c to out until c is closed, then calls wg.Done.
-  send := func(c <-chan int) {
-    for n := range c {
-      out <- n
-    }
-    wg.Done()
-  }
-
-  wg.Add(len(cs))
-  for _, c := range cs {
-    go send(c)
-  }
-
-  // Start a goroutine to close out once all the send goroutines are
-  // done.  This must start after the wg.Add call.
-  go func() {
-    wg.Wait()
-    close(out)
-  }()
-  return out
-}
-```
-
-The `Merge` function converts a list of channels to a single channel by starting a goroutine for each inbound channel that copies the values to the sole outbound channel.
-
-Once all the output goroutines have been started, `Merge` a goroutine is started to close the main channel.

gomore/04_fan_in/fan_in_test.go

@@ -5,22 +5,30 @@ import (
 	"testing"
 )
 
-func TestFanIn(T *testing.T) {
-	randomNumbers := []int{13, 44, 56, 99, 9, 45, 67, 90, 78, 23}
+func TestMergeDataSeq(T *testing.T) {
+
+	//第一路输入源
+	dataStreams1 := []int{13, 44, 56, 99, 9, 45, 67, 90, 78, 23}
 	// generate the common channel with inputs
-	inputChan := generatePipeline(randomNumbers)
+	inputChan1 := generateNumbersPipeline(dataStreams1)
 
-	// Fan-out to 2 Go-routine
-	c1 := squareNumber(inputChan)
-	c2 := squareNumber(inputChan)
+	//第二路输入源
+	dataStreams2 := []int{2, 4, 6, 9, 1, 1, 2, 3, 7, 8}
+
+	inputChan2 := generateNumbersPipeline(dataStreams2)
+
+	c1 := squareNumber(inputChan1)
+
+	c2 := squareNumber(inputChan2)
+
+	//fanIn data for the squared numbers
+	out := Merge(c1, c2)
 
-	// Fan-in the resulting squared numbers
-	c := fanIn(c1, c2)
 	sum := 0
 
-	// Do the summation
-	for i := 0; i < len(randomNumbers); i++ {
-		sum += <-c
+	for c := range out {
+		sum += c
 	}
-	fmt.Printf("Total Sum of Squares: %d", sum)
+
+	fmt.Printf("Total Sum of Squares by FanIn : %d\n", sum)
 }