Hi, I am having some issues with staticCFunction. ...

# kotlin-native

[Thomas]

Hi, I am having some issues with staticCFunction. See code below:

val identityBytes: ByteArray = someValue()
val pskBytes: ByteArray = someValue()

// <https://www.openssl.org/docs/man1.0.2/man3/SSL_CTX_set_psk_client_callback.html>

SSL_CTX_set_psk_client_callback(ctx, staticCFunction { ssl, hint, identity, maxIdentityLen, psk, maxPskLen ->
    require(identityBytes.size <= maxIdentityLen.toInt())
    require(pskBytes.size <= maxPskLen.toInt())

    identityBytes.forEachIndexed { index, value ->
        identity!![index] = value
    }
    pskBytes.forEachIndexed { index, value ->
        psk!![index] = value.toUByte()
    }

    // ...
    TODO()
})

When compiling this gives an error:

kotlinx.cinterop.staticCFunction must take an unbound, non-capturing function or lambda

I need to access identityBytes and pskBytes from this lambda. Is that possible?

[olonho]

C function != complete Kotlin lambda, all state must come explicitly as an argument or be obtained from the global.

[Thomas]

@olonho Hmm, in this example I pass the staticCFunction to another function (SSL_CTX_set_psk_client_callback) which is not mine. How am I supposed to write the bytes in the C function if I can not access identityBytes and pskBytes?

[Thomas]

I don’t see how I could pass the two byte arrays as an argument in this example

[Thomas]

Global variables are not an option either as the two byte arrays are not the same for every user and are returned from another network request

[olonho]

there’s no difference from C, I guess. How would you pass those parameters into C callback? From https://github.com/Chronic-Dev/openssl/blob/master/ssl/ssltest.c seems everything needed is passed as an argument callback.