知识点 文件读写

package main

import (
   "bufio"
   "fmt"
   "io/ioutil"
   "os"
   "time"
)

// os.Open
func read1(filepath string) string {
   f, err := os.Open(filepath)
   if err != nil {
      panic(err)
   }
   defer f.Close()
   chunks := make([]byte, 1024, 1024)
   buf := make([]byte, 1024)
   for {
      n, err := f.Read(buf)
      if err != nil || 0 == n {
         break
      }
      chunks = append(chunks, buf[:n]...)
   }
   return string(chunks)
}

// bufio
func read2(filepath string) string {
   file, err := os.Open(filepath)
   if err != nil {
      panic(err)
   }
   defer file.Close()
   chunks := make([]byte, 1024, 1024)
   f := bufio.NewReader(file)
   buf := make([]byte, 1024)
   for {
      n, err := f.Read(buf)
      if err != nil || 0 == n {
         break
      }
      chunks = append(chunks, buf[:n]...)
   }
   return string(chunks)
}

// ioutil
func read3(filepath string) string {
   file, err := os.Open(filepath)
   if err != nil {
      panic(err)
   }
   defer file.Close()
   f, _ := ioutil.ReadAll(file)
   txt := string(f)
   return txt
}

func main() {
   filepath := "somefile.txt"
   t1 := time.Now()
   read1(filepath)
   elapsed1 := time.Since(t1)
   fmt.Println("cost ", elapsed1)
   t2 := time.Now()
   read2(filepath)
   elapsed2 := time.Since(t2)
   fmt.Println("cost ", elapsed2)
   t3 := time.Now()
   read3(filepath)
   elapsed3 := time.Since(t3)
   fmt.Println("cost ", elapsed3)
}