How to convert CPointer<ByteVar>? to Int Value/ I try it.reinterpret<IntVar>().pointed.v...

# kotlin-native

[levcom]

How to convert CPointer<ByteVar>? to Int Value/ I try it.reinterpret<IntVar>().pointed.value, but did't work

[msink]

there are unsafe casts between CPointer<T>? and Long available, provided by .toLong() and .toCPointer<T>() extension methods:

val longValue = ptr.toLong()
val originalPtr = longValue.toCPointer<T>()

[levcom]

I think, need to convert the binary value (in CPointer<T>?) to the reverse order byte (from network byte order to local byte order), and then unsafe casts CPointer<T>? to <IntVar>. But I don't understand how Kotlin/Native support binary types.

[msink]

ptr.toLong() is C (int)ptr
val.toCPointer<T> is C (T*)val

[msink]

if you want not pointer itself but value it points to, then better do something like
val ipaddr = (ptr[0] << 24) or (ptr[1] << 16) or (ptr[3] << 8) or (ptr[3])

[olonho]

What exactly are trying to achieve?

[olonho]

if you really need byte order conversion, take a look at https://github.com/JetBrains/kotlin-native/blob/master/samples/socket/src/main/kotlin/EchoServer.kt#L43

[levcom]

I get: val value = PQgetvalue(res, j, i) (value : CPointer<ByteVar>?)

[levcom]

I want (on С lang.): val = ntohl(\*((uint32_t \*) value))

[levcom]

I write on Kotlin: val val = PQgetvalue(res, j, i)?.let {
val result = ntohl(it.reinterpret<IntVar>().pointed.value) \n result
} ?: 0

[levcom]

or "ntohl(it.reinterpret<IntVar>()[0])"

[levcom]

But I don't get right value

[msink]

*((u32*)value) is bad idea - not portable, works only on x86 if not aligned on x4 boundary
linux kernel have macro get_unaligned_be32 and similar, implemented by byte reads and shifts.

[levcom]

Thank you all for your help! I studied examples EchoServer.kt and other ex. with native C-functions. I use ntohl/htonl functions from package platform.posix.*