Kotlinの各型とByte配列の相互変換

ConvertByteArrayTo.kt

//  [0x00, 0xff] -> "00ff" 
fun ByteArray.toHexString(asReverse: Boolean = false): String = 
    map { String.format("%02x", it) }
        .let { if (asReverse) it.asReversed() else it }
        .joinToString("")

//  2byte (Little Endian)
fun ByteArray.toShort(): Short {
    var result: Int = 0
    for (i in 0 until count()) {
        result = result or (get(i).toUByte().toInt() shl 8 * i)
    }
    return result.toShort()
}

//  4byte (Little Endian)
fun ByteArray.toInt(): Int {
    var result: Int = 0
    for (i in 0 until count()) {
        result = result or (get(i).toUByte().toInt() shl 8 * i)
    }
    return result
}

//  8byte (Little Endian)
fun ByteArray.toLong(): Long {
    var result: Long = 0
    for (i in 0 until count()) {
        result = result or (get(i).toUByte().toLong() shl 8 * i)
    }
    return result
}

//  4byte (Little Endian)
fun ByteArray.toFloat() = intBitsToFloat(toInt())

//  8byte (Little Endian)
fun ByteArray.toDouble() = longBitsToDouble(toLong())

ConvertToByteArray.kt

//  "00ff" -> [0x00, 0xff]
fun String.asByteArray(): ByteArray {
    val hexString = if (length % 2 == 0) this else "0${this}"
    return hexString.chunked(2).map { it.asByte() }.toByteArray()
}

//  "00" -> [0x00]
fun String.asByte() = substring(0, 2).toShort(16).toByte()

//  2byte (Little Endian)
fun Short.toBytes(): ByteArray {
    var l = this.toInt()
    val result = ByteArray(2)
    for (i in 0..1) {
        result[i] = (l and 0xff).toByte()
        l = l shr 8
    }
    return result
}

//  4byte (Little Endian)
fun Int.toBytes(): ByteArray {
    var l = this
    val result = ByteArray(4)
    for (i in 0..3) {
        result[i] = (l and 0xff).toByte()
        l = l shr 8
    }
    return result
}

//  8byte (Little Endian)
fun Long.toBytes():ByteArray {
    var l = this
    val result = ByteArray(8)
    for (i in 0..7) {
        result[i] = (l and 0xFF).toByte()
        l = l shr 8
    }
    return result
}

//  4byte (Little Endian)
fun Float.toBytes() = toRawBits().toBytes()

//  8byte (Little Endian)
fun Double.toBytes() = toRawBits().toBytes()