all tasks

Task/Synchronous-concurrency/Go/synchronous-concurrency.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+    "fmt"
+    "bufio"
+    "io"
+    "os"
+)
+
+// main, one of two goroutines used, will function as the "reading unit"
+func main() {
+    // get file open first
+    f, err := os.Open("input.txt")
+    if err != nil {
+        fmt.Println(err)
+        return
+    }
+    defer f.Close()
+    lr := bufio.NewReader(f)
+
+    // that went ok, now create communication channels,
+    // and start second goroutine as the "printing unit"
+    lines := make(chan string)
+    count := make(chan int)
+    go printer(lines, count)
+
+    for {
+        line, prefix, err := lr.ReadLine()
+        switch {
+        case err == io.EOF:
+        case err != nil:
+            fmt.Println(err)
+        case prefix:
+            fmt.Println("unexpected long line")
+        default:
+            lines <- string(line)
+            continue
+        }
+        break
+    }
+    // this represents the request for the printer to send the count
+    close(lines)
+    // wait for the count from the printer, then print it, then exit
+    fmt.Println("Number of lines:", <-count)
+}
+
+func printer(in <-chan string, count chan<- int) {
+    c := 0
+    // loop as long as in channel stays open
+    for s := range in {
+        fmt.Println(s)
+        c++
+    }
+    // make count available on count channel, then return (terminate goroutine)
+    count <- c
+}