Zgo - randInt, randString

 

package main

import (
    crand "crypto/rand"
    "encoding/base64"
    "fmt"
    mrand "math/rand"
    "strings"
)

const (
    // As we only want to get printable ASCII characters, we limit the range of pseudo-random numbers
    // that can be generated. The total number of printable characters in the ASCII table is 94. This means
    // that the range of the pseudo-random numbers that the program can generate should be from 0
    // to 94, without including 94. Therefore, the values of the MIN and MAX global variables, 
    // are 0 and 94, respectively.
    MIN = 0
    MAX = 94
)

func main() {
    fmt.Println(randString(20))
    randBytes := generateBytes(20)
    fmt.Println(string(randBytes))
    fmt.Println(base64.URLEncoding.EncodeToString(randBytes))
}

func randInt(min, max int) int {
    // Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n) from the default [Source]. It panics if n <= 0.
    return mrand.Intn(max - min) + min
}

func randString(len int64) string {
    // The startChar variable holds the first ASCII character that can be generated by the utility, which,
    // in this case, is the exclamation mark, which has a decimal ASCII value of 33.
    startChar := "!"

    sb := strings.Builder{}
    var i int64 = 1
    for {
        myRand := randInt(MIN, MAX)
        newChar := string(startChar[0] + byte(myRand))
        sb.WriteString(newChar)

        if i == len {
            break
        }
        i++
    }

    return sb.String()
}

func generateBytes(n int64) []byte {
    b := make([]byte, n)
    // The rand.Read() function randomly generates numbers that occupy the entire b byte slice. You
    // need to decode that byte slice using base64.URLEncoding.EncodeToString(b) in order to get
    // a valid string without any control or unprintable characters.
    crand.Read(b)  // The Read function always returns len(b) and a nil error, so no need to handle the error.
    return b
}