How to right using CRC32 on Android

Question

I'm using java.util.zip.CRC32 for calculate CRC32. I was detecting weird feature; my app connecting with devices where CRC32 calculated by char array, see simple test:

    val i: Int = 123456789
    val crc32 = CRC32Any()

    crc32.reset()
    crc32.update(i)
    Timber.i ("CRC32 by int '$i': ${crc32.value}")

    crc32.reset()
    var arr = ByteBuffer.allocate(Int.SIZE_BYTES)
            .putInt(i)
            .array()
    crc32.update(arr)
    Timber.i ("CRC32 by array '${arr.toHexString()}': ${crc32.value}")

    crc32.reset()
    arr.reverse()
    crc32.update(arr)
    Timber.i ("CRC32 by reverse arr '${arr.toHexString()}': ${crc32.value}")

And as result:

CRC32 by int '123456789': 3219065702
CRC32 by array '075BCD15': 3488836380
CRC32 by reverse arr '15CD5B07': 417295518

All CRC32 don't match! How to calculate right CRC32 with java.util.zip.CRC32 for correct use?

Answer 1

Solution:

@ExperimentalUnsignedTypes
fun toByteArray(any: Any?): ByteArray =
        when(any){
            is ByteArray -> any
            is ByteBuffer -> (any as ByteBuffer).array()
            is String -> (any as String).toByteArray()
            is Char ->
                ByteBuffer.allocate(Char.SIZE_BYTES)
                        .putChar(any as Char)
                        .array()
            is Byte ->
                ByteBuffer.allocate(Byte.SIZE_BYTES)
                        .put(any)
                        .array()
            is UByte ->
                ByteBuffer.allocate(UShort.SIZE_BYTES)
                        .putShort((any as UByte).toShort())
                        .array()
                        .also { it.reverse() }
                        .copyOfRange(0, UByte.SIZE_BYTES)
            is Int ->
                ByteBuffer.allocate(Int.SIZE_BYTES)
                        .putInt(any as Int)
                        .array()
                        .also { it.reverse() }
            is UInt ->
                ByteBuffer.allocate(Long.SIZE_BYTES)
                        .putLong((any as UInt).toLong())
                        .array()
                        .also { it.reverse() }
                        .copyOfRange(0, UInt.SIZE_BYTES)
            is Long ->
                ByteBuffer.allocate(Long.SIZE_BYTES)
                        .putLong(any as Long)
                        .array()
                        .also { it.reverse() }
            //is ULong -> // not supported now
            else ->
                ByteArray(0)
        }

class CRC32Any: CRC32() {
    @Throws(IOException::class)
    fun updateAny(any: Any?) {
        if (any != null)
            when (any) {
                is File -> updateFromFile(any)
                else -> super.update(toByteArray(any))
            }
    }

    @Throws(IOException::class)
    private fun updateFromFile(file: File) {
        if (!(file?.exists()))
            throw Exception("Source file not found!")

        val inFile = FileInputStream(file)
        val buf = ByteBuffer.allocate(2048)
        var size: Int = 0
        while (inFile.channel.read(buf).also { size = it } !== -1) {
            buf.flip()
            super.update(buf.array(), 0, size)
            buf.clear()
        }
        inFile.close()
    }
}