Вариантдополнения

import kotlin.io.encoding.*
import kotlin.test.*

fun main() { 
   //sampleStart 
   val format = HexFormat {
    upperCase = true
    bytes.byteSeparator = " "
}

val bytes = byteArrayOf(0xDE.toByte(), 0x2D, 0x02, 0xC0.toByte())

// The Base64.Default instance is configured with PaddingOption.PRESENT
println(Base64.Default.encode(bytes)) // 3i0CwA==
println(Base64.Default.decode("3i0CwA==").toHexString(format)) // DE 2D 02 C0
// PaddingOption.PRESENT requires the decode input to be properly padded
// Base64.Default.decode("3i0CwA") // will fail with IllegalArgumentException

// Create a new instance with PaddingOption.ABSENT that uses the Base64.Default alphabet
val base64AbsentPadding = Base64.Default.withPadding(Base64.PaddingOption.ABSENT)

println(base64AbsentPadding.encode(bytes)) // 3i0CwA
println(base64AbsentPadding.decode("3i0CwA").toHexString(format)) // DE 2D 02 C0
// PaddingOption.ABSENT requires the decode input not to be padded
// base64AbsentPadding.decode("3i0CwA==") // will fail with IllegalArgumentException

// Create a new instance with PaddingOption.PRESENT_OPTIONAL that uses the Base64.Default alphabet
val base64PresentOptionalPadding = Base64.Default.withPadding(Base64.PaddingOption.PRESENT_OPTIONAL)

println(base64PresentOptionalPadding.encode(bytes)) // 3i0CwA==
// PaddingOption.PRESENT_OPTIONAL allows both padded and unpadded decode inputs
println(base64PresentOptionalPadding.decode("3i0CwA==").toHexString(format)) // DE 2D 02 C0
println(base64PresentOptionalPadding.decode("3i0CwA").toHexString(format)) // DE 2D 02 C0
// However, partially padded input is prohibited
// base64PresentOptionalPadding.decode("3i0CwA=") // will fail with IllegalArgumentException

// Create a new instance with PaddingOption.ABSENT_OPTIONAL that uses the Base64.Default alphabet
val base64AbsentOptionalPadding = Base64.Default.withPadding(Base64.PaddingOption.ABSENT_OPTIONAL)

println(base64AbsentOptionalPadding.encode(bytes)) // 3i0CwA
// PaddingOption.ABSENT_OPTIONAL allows both padded and unpadded decode inputs
println(base64AbsentOptionalPadding.decode("3i0CwA").toHexString(format)) // DE 2D 02 C0
println(base64AbsentOptionalPadding.decode("3i0CwA==").toHexString(format)) // DE 2D 02 C0
// However, partially padded input is prohibited
// base64AbsentOptionalPadding.decode("3i0CwA=") // will fail with IllegalArgumentException 
   //sampleEnd
}