Golang : Chunk split or divide a string into smaller chunk example

Problem:

You need a function in Golang that are similar to PHP's chunk_split() function that can split a string into smaller chunks. It is commonly used in converting base64 encoded string to match RFC 2045 semantics. Such as line-breaking base64 encoded lines at 76 characters.

Excerpt from https://www.ietf.org/rfc/rfc2045.txt

(5) Encoded lines must not be longer than 76 characters, not counting the trailing CRLF. If longer lines are found in incoming, encoded data, a robust implementation might nevertheless decode the lines, and might report the erroneous encoding to the user.

Solution:

This code example below should do the job on dividing a string into smaller chunks.

 package main

 import (
 "fmt"
 )

 func chunkSplit(body string, limit int, end string) string {

 var charSlice []rune

 // push characters to slice
 for _, char := range body {
 charSlice = append(charSlice, char)
 }

 var result string = ""

 for len(charSlice) >= 1 {
 // convert slice/array back to string
 // but insert end at specified limit

 result = result + string(charSlice[:limit]) + end

 // discard the elements that were copied over to result
 charSlice = charSlice[limit:]

 // change the limit
 // to cater for the last few words in
 // charSlice
 if len(charSlice) < limit {
 limit = len(charSlice)
 }

 }

 return result

 }

 func main() {
 before := "this is a long string that needs to be chunked into smaller chunks"

 // chunk after 30 characters and append with newline
 // for RFC 2045, change limit from 30 to 76
 after := chunkSplit(before, 30, "\n")

 fmt.Println("Before :\n", before)
 fmt.Println("After :\n", after)
 }

Output:

Before :

this is a long string that needs to be chunked into smaller chunks

After :

this is a long string that nee

ds to be chunked into smaller

chunks

References:

https://socketloop.com/tutorials/golang-warp-text-string-by-number-of-characters-or-runes-example

https://tools.ietf.org/html/rfc7230#section-4.1

http://php.net/manual/en/function.chunk-split.php