I want to get size of the original file from a string variable, which is obtained by using a base64 encode file.
package main
import (
"bufio"
"encoding/base64"
"io/ioutil"
"os"
)
func encodeFile(file string) string {
f, err := os.Open(file)
if err != nil {
panic(err)
}
reader := bufio.NewReader(f)
content, _ := ioutil.ReadAll(reader)
encoded := base64.StdEncoding.EncodeToString(content)
return encoded
}
func main() {
datas := encodeFile("/tmp/hello.json")
//how to get file size from datas
}
how to get the file size from datas? thks.
This should do it:
func calcOrigBinaryLength(datas string) int {
l := len(datas)
// count how many trailing '=' there are (if any)
eq := 0
if l >= 2 {
if datas[l-1] == '=' {
eq++
}
if datas[l-2] == '=' {
eq++
}
l -= eq
}
// basically:
//
// eq == 0 : bits-wasted = 0
// eq == 1 : bits-wasted = 2
// eq == 2 : bits-wasted = 4
// each base64 character = 6 bits
// so orig length == (l*6 - eq*2) / 8
return (l*3 - eq) / 4
}
Playground validation: https://play.golang.org/p/Y4v102k74V5
Well, base64 encoded string has different length then original file. To get original size you can do next: 1. In function encodeFile return len(content) which is size of original file.
x = (n * (3/4)) - y Where:
len(datas)