CODEWITHSUNDEEP
arrayskotlintype-conversion
user2186425
user2186425

Reputation: 475

ByteArray to Float in kotlin

I have a 4 bytes array which represent a float value. Since kotlin lack of bitwise operations for Byte how can I convert it to float in most optimal way?

Upvotes: 12

Views: 13656

Answers (2)

Splitframe
Splitframe

Reputation: 434

I stumbled upon this and here is how I use it, if I am not mistaken this should be Kotlin Native 1.3:

fun to4ByteArray(value: Int): ByteArray {
    return byteArrayOf(
        value.toByte(),
        (value shr 8).toByte(),
        (value shr 16).toByte(),
        (value shr 24).toByte(),
    )
}

fun to4ByteArray(value: Float): ByteArray {
    val bitRep = value.toRawBits()
    return byteArrayOf(
        bitRep.toByte(),
        (bitRep shr 8).toByte(),
        (bitRep shr 16).toByte(),
        (bitRep shr 24).toByte(),
    )
}

fun intFrom4ByteArray(value: ByteArray): Int {
    if(value.size != 4) return 0
    return  (value[3].toInt() and 0xff shl 24) or
            (value[2].toInt() and 0xff shl 16) or
            (value[1].toInt() and 0xff shl 8) or
            (value[0].toInt() and 0xff)

}

fun floatFrom4ByteArray(value: ByteArray): Float {
    if(value.size != 4) return 0.0f
    return Float.fromBits(
        (value[3].toInt() and 0xff shl 24) or
        (value[2].toInt() and 0xff shl 16) or
        (value[1].toInt() and 0xff shl 8) or
        (value[0].toInt() and 0xff)
    )
}

Upvotes: 0

hotkey
hotkey

Reputation: 147941

You can use the Java NIO ByteBuffer, it has the getFloat() and getFloat(index) functions for that:

val bytes = byteArrayOf(1, 2, 3, 4)

val buffer = ByteBuffer.wrap(bytes)
val float1 = buffer.getFloat()  // Uses current position and increments it by 4
val float2 = buffer.getFloat(0) // Uses specified position

Upvotes: 20

Related Questions