p := make([]byte, 5)
fmt.Println(reflect.TypeOf(reader)) //*io.LimitedReader
var total int
for {
n, err := reader.Read(p)
if err == io.EOF {
fmt.Println("read value", string(p[:total])) //read value hello
fmt.Println(total) //5
break
}
total = total + n
}
}
(2)func MultiReader(readers ...Reader) Reader这个函数一看就知道是封装了多个readers,跟上边的方法差不多，只是封装了多个而已，当然还去除了读取的限制，我们代码给大家测试一下
import (
"fmt"
"io"
"os"
"reflect"
)
func main() {
f1, _ := os.Open("test1.txt")
f2, _ := os.Open("test.txt")
defer f1.Close()
defer f2.Close()
reader := io.MultiReader(f1, f2) //*io.multiReader
fmt.Println(reflect.TypeOf(reader))
p := make([]byte, 10)
var total int
var data string
for {
n, err := reader.Read(p)
if err == io.EOF {
fmt.Println("read end", total) //read end 17
break
}
total = total + n
data = data + string(p[:n])
}
fmt.Println("read value", data) //read value widuu2hello widuu
fmt.Println("read count", total) // read count 17
}
(3)既然上边介绍读了，我这介绍个写吧type Write`func MultiWriter(writers ...Writer) Writer一样的作用只不过是这次换成写了
import (
"fmt"
"io"
"io/ioutil"
"os"
)
func main() {
f1, _ := os.Create("1.txt")
f2, _ := os.Create("2.txt")
writer := io.MultiWriter(f1, f2)
writer.Write([]byte("widuu"))
//千万别这么逻辑来 ，我这是测试用的哈
r1, _ := ioutil.ReadFile("1.txt")
r2, _ := ioutil.ReadFile("2.txt")
fmt.Println(string(r1)) //widuu
fmt.Println(string(r2)) //widuu
}
(4)func TeeReader(r Reader, w Writer) Reader这个方法有意思是从r中读取数据然后写入到w中，这个没有内部缓冲区，看下代码
import (
"fmt"
"io"
"os"
"reflect"
)
func main() {
r, _ := os.Open("test.txt")
w, _ := os.Create("test2.txt")
reader := io.TeeReader(r, w)
fmt.Println(reflect.TypeOf(reader)) //*io.teeReader
p := make([]byte, 10)
n, _ := reader.Read(p)
