PRESENT_OPTIONAL
Pad on encode, allow optional padding on decode.
When encoding, the result is padded with '=' to reach an integral multiple of 4 symbols. When decoding, the input may be either padded or unpadded. If the input contains a padding character, the correct amount of padding character(s) must be present. The padding character '=' marks the end of the encoded data, and subsequent symbols are prohibited.
Samples
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())
val base64PresentOptionalPadding = Base64.Default.withPadding(Base64.PaddingOption.PRESENT_OPTIONAL)
// PaddingOption.PRESENT_OPTIONAL pads on encode
println(base64PresentOptionalPadding.encode(bytes)) // 3i0CwA==
// It 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
//sampleEnd
}