androidreadchannel.kt

class AndroidReadChannel(private val delegate: ByteReadChannel) : ByteReadChannel by delegate {
    suspend fun read(): TransportResponse {
        val bytes = ByteArray(4)
        delegate.readFully(bytes, 0, 4)

        val ok = bytes.isOkay()
        val message = if (!ok) {
            delegate.readFully(bytes, 0, 4)
            val responseLength = String(bytes, Const.DEFAULT_TRANSPORT_ENCODING)
            val errorMessageLength = responseLength.toIntOrNull(16)
            if (errorMessageLength == null) {
                log.warn { "Unexpected error message length $responseLength" }
                null
            } else {
                val errorBytes = ByteArray(errorMessageLength)
                delegate.readFully(errorBytes, 0, errorMessageLength)
                String(errorBytes, Const.DEFAULT_TRANSPORT_ENCODING)
            }
        } else {
            null
        }

        return TransportResponse(ok, message)
    }

    private fun ByteArray.isOkay(): Boolean {
        return this[0] == 'O'.toByte() &&
                this[1] == 'K'.toByte() &&
                this[2] == 'A'.toByte() &&
                this[3] == 'Y'.toByte()
    }
}