How to seek in file use bufio.Reader?

[hui zhang]

I am using  bufio.Reader  and binary.Read 

to read binary from file,  I want to seek in the file or bufio.Reader

Below code does not work 

fi.Seek(0, os.SEEK_SET) ////Does not work for bufio.Reader

below definition shows that r control the position , but I did not see any method to set it

type Reader struct {
   buf          []byte
   rd           io.Reader // reader provided by the client
   r, w         int       // buf read and write positions
   err          error
   lastByte     int
   lastRuneSize int
}

I expect below code to output 3.13 twice ,   but it output 3.13   3.14

package main

import (
   _ "bytes"
   "fmt"
   _ "math"

   "bufio"
   "encoding/binary"
   "os"
)

func main() {
   var pi float64
   //b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40,
   //         0x78, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40}
   //buf := bytes.NewReader(b)
   //err := binary.Read(buf, binary.LittleEndian, &pi)
   //if err != nil {
   // fmt.Println("binary.Read failed:", err)
   //}
   //fmt.Println(pi)
   //// Output: 3.141592653589793
   //err = binary.Read(buf, binary.LittleEndian, &pi)
   //if err != nil {
   // fmt.Println("binary.Read failed:", err)
   //}
   //fmt.Println(pi)
   //------------------------------------------------------------
   // open output file
   fo, err := os.Create("./output.bin")
   if err != nil {
      panic(err)
   }

   // make a write buffer
   var fl1 float64 = 3.13
   var fl2 float64 = 3.14
   w := bufio.NewWriter(fo)
   err = binary.Write(w, binary.LittleEndian, fl1)
   if err != nil {
      fmt.Println("binary.Write failed:", err)
   }
   err = binary.Write(w, binary.LittleEndian, fl2)
   if err != nil {
      fmt.Println("binary.Write failed:", err)
   }
   w.Flush()
   // close fo on exit and check for its returned error
   if err := fo.Close(); err != nil {
      panic(err)
   }

   //------------------------------------------------------------
   fi, err := os.Open("./output.bin")
   if err != nil {
      panic(err)
   }
   // close fi on exit and check for its returned error
   defer func() {
      if err := fi.Close(); err != nil {
         panic(err)
      }
   }()

   rd := bufio.NewReader(fi)
   err = binary.Read(rd, binary.LittleEndian, &pi)
   if err != nil {
      fmt.Println("binary.Read failed:", err)
   }
   fmt.Println(pi)

   fi.Seek(0, os.SEEK_SET) ////Does not work for bufio.Reader

   err = binary.Read(rd, binary.LittleEndian, &pi)
   if err != nil {
      fmt.Println("binary.Read failed:", err)
   }
   fmt.Println(pi)

}

[Konstantin Khomoutov]

On Wed, 18 Jan 2017 23:35:30 -0800 (PST)
hui zhang <fastf...@gmail.com> wrote:

> I am using bufio.Reader and binary.Read
> to read binary from file, I want to seek in the file or bufio.Reader
> Below code does not work
>
> fi.Seek(0, os.SEEK_SET) ////Does not work for bufio.Reader
>
>
> below definition shows that r control the position , but I did not
> see any method to set it

That's Reset(), as I've already explained in this mail thread.