CharsetDecoder.kt

//https://www.ne.jp/asahi/hishidama/home/tech/java/Buffer.html#h_CharsetDecoder

val input = "0あいう" +
                    ubyteArrayOf(0xE9U, 0x82U, 0x8AU, 0xF3U, 0xA0U, 0x84U, 0x80U).toByteArray().toString(Charsets.UTF_8) +
                ubyteArrayOf(0xF0U, 0x9FU, 0x98U, 0x8aU).toByteArray().toString(Charsets.UTF_8)
            val stream = input.byteInputStream()
            val decoder = Charsets.UTF_8.newDecoder()
            val byteBuffer = ByteBuffer.allocate(4)
            val charBuffer = CharBuffer.allocate(2)
            var eof = false
            while(!eof) {
                val byte = stream.read()
                if (0 <= byte) {
                    byteBuffer.put(byte.toByte())
                } else {
                    eof = true
                }
                byteBuffer.flip()
                var result = decoder.decode(byteBuffer, charBuffer, eof)
                if (!result.isUnderflow) {
                    result.throwException()
                }
                if (eof) {
                    result = decoder.flush(charBuffer)
                    if (!result.isUnderflow) {
                        result.throwException()
                    }
                }
                charBuffer.flip()
                while(charBuffer.hasRemaining()) {
                    val c = charBuffer.get()
                    println("${c}-[0x${Integer.toHexString(c.code).uppercase()}]")
                }
                if (byteBuffer.hasRemaining()) {
                    println("compact")
                    byteBuffer.compact()
                } else {
                    byteBuffer.clear()
                }
                charBuffer.clear()
            }