rateprinter.go

/*
Design a Rate Printer
The printer reads from a file
The printer writes to a file
Print the Bytes/Second at which the printer is printing every second
*/
package main

import (
	"fmt"
	"io"
	"log"
	"os"
	"time"
)

var dataread chan int
var data chan []byte

func main() {
	dataread = make(chan int, 100)
	data = make(chan []byte, 100)
	go reader("/dev/zero")
	go writer("/dev/null")
	totalBytes := 0
	start := time.Now()
	var t time.Time
	var rate float64
	var diff time.Duration
	for {
		d := <-dataread
		totalBytes += d
		t = time.Now()
		diff = t.Sub(start)
		if diff > 1*time.Second {
			rate = float64(totalBytes) / (float64(diff) / float64(time.Second))
			fmt.Println("Rate: Bytes/Second", rate)
			start = t
		}
	}

}

func reader(s string) {
	var err error
	rc, err := os.Open(s)
	if err != nil {
		log.Fatal(err)
	}
	buf := make([]byte, 10)
	for {
		if _, err = io.ReadAtLeast(rc, buf, 4); err != nil {
			log.Fatal(err)
		}
		dataread <- len(buf)
		data <- buf
		buf = make([]byte, 10)
	}
}

func writer(f string) {
	for {
		<-data
	}
}