decodeIntoByteArray

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

fun main() { 
   //sampleStart 
   val outputBuffer = ByteArray(1024)
// {data:\"ZW5jb2RlZA==\"}
val data = byteArrayOf(
    123, 100, 97, 116, 97,
    58, 34, 90, 87, 53, 106,
    98, 50, 82, 108, 90, 65,
    61, 61, 34, 125
)
val from = data.indexOf('"'.code.toByte()) + 1
val until = data.lastIndexOf('"'.code.toByte())

// decode subrange of input data into buffer and remember how many bytes were written
val bytesWritten = Base64.decodeIntoByteArray(data, destination = outputBuffer, startIndex = from, endIndex = until)
println(outputBuffer.decodeToString(endIndex = bytesWritten)) // encoded 
   //sampleEnd
}

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

fun main() { 
   //sampleStart 
   val outputBuffer = ByteArray(1024)
val inputChunks = listOf("Q2h1bmsx", "U2Vjb25kQ2h1bms=", "Y2h1bmsjMw==")

var bufferPosition = 0
val chunkIterator = inputChunks.iterator()
while (bufferPosition < outputBuffer.size && chunkIterator.hasNext()) {
    val chunk = chunkIterator.next()
    // fill buffer with data decoded from base64-encoded chunks
    // and increment current position by the number of decoded bytes
    bufferPosition += Base64.decodeIntoByteArray(
        chunk,
        destination = outputBuffer,
        destinationOffset = bufferPosition
    )
}
// consume outputBuffer
println(outputBuffer.decodeToString(endIndex = bufferPosition)) // Chunk1SecondChunkchunk#3 
   //sampleEnd
}