Kotlin UUID to Base64 and vice versa

uuid-to-base64.kt

import java.nio.ByteBuffer
import java.nio.charset.Charset
import java.util.*

fun UUID.toBase64(): ByteArray {
    val byteArray = ByteBuffer.allocate(16)
        .putLong(this.mostSignificantBits)
        .putLong(this.leastSignificantBits)
        .array()
    return Base64.getEncoder().encode(byteArray)
}

fun ByteArray.toUUID(): UUID {
    try {
        val dec = Base64.getDecoder().decode(this)

        if (dec.size != 16) {
            throw IllegalArgumentException("UUIDs can only be created from 128bit")
        }
        val buf = ByteBuffer.allocate(16).put(dec)
        return UUID(buf.getLong(0), buf.getLong(8))
    } catch (e: IllegalArgumentException) {
        throw IllegalArgumentException("Invalid Base64 sequence", e)
    }
}

fun UUID.toBase64String() = String(this.toBase64())
fun String.toUUID(charset: Charset = Charsets.UTF_8) = this.toByteArray(charset).toUUID()

fun main() {
    val uuid = UUID.randomUUID()
    println(uuid)
    val enc = uuid.toBase64String()
    println(enc)
    val dec = enc.toUUID()
    println(dec)
    print(uuid == dec)
}