Golang : Read from buffered reader until specific number of bytes

Problem :

You have a buffered reader streaming in with data. You want to limit each read to a specific size for processing purpose before advancing to the next read.

Solution :

Specify the size of the buffer (p) to the limit you want per read. Use io.ReadFull to consume data from the buffered reader and fill up to the buffer (p in the code example below) max size.

 package main

 import (
 "fmt"
 "io"
 "strings"
 )

 func main() {
 reader := strings.NewReader("Profession.socketloop.com says Hello World!")

 // the read is limited by the size of p
 p := make([]byte, 32)

 fmt.Printf("Read until %d bytes and advance the reader\n", len(p))

 n, err := io.ReadFull(reader, p) // read all bytes into buffer

 // NOTE : this is just a simple tutorial to demonstrate how to limit your read to certain
 // size. You might want to turn this into a loop
 // to read the buffered reader until EOF

 fmt.Printf("\n%s ", p)

 fmt.Printf("\n Number of bytes copied : %d with error : %v\n", n, err)

 }

Output :

Read until 32 bytes and advance the reader

Profession.socketloop.com says H

Number of bytes copied : 32 with error :

NOTE : this is just a simple tutorial to demonstrate how to limit your read to certain size with a fixed size strings buffered reader. You might want to turn this into a loop to continuously read the buffered reader stream data until EOF.

Reference :

http://golang.org/pkg/io/#ReadFull