Copy input stream in Kotlin with progress

InputStreamUtil.kt

import java.io.InputStream
import java.io.OutputStream

fun InputStream.copyTo(out: OutputStream, onCopy: (totalBytesCopied: Long, bytesJustCopied: Int) -> Any): Long {
    var bytesCopied: Long = 0
    val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
    var bytes = read(buffer)
    while (bytes >= 0) {
        out.write(buffer, 0, bytes)
        bytesCopied += bytes
        onCopy(bytesCopied, bytes)
        bytes = read(buffer)
    }
    return bytesCopied
}

In case this helps someone, here is the version using Flow emitting progress in percentage:

fun InputStream.copyTo(out: OutputStream, streamSize: Long): Flow<Int> {
    return flow {
        var bytesCopied: Long = 0
        val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
        var bytes = read(buffer)
        while (bytes >= 0) {
            out.write(buffer, 0, bytes)
            bytesCopied += bytes
            // Emit stream progress in percentage
            emit((bytesCopied * 100 / streamSize).toInt())
            bytes = read(buffer)
        }
    }.flowOn(Dispatchers.IO).distinctUntilChanged()
}