Flexpage example?

Hello, is there any Flexpage reference example? I want to push a buffer, i.e. a pointer and the size of it to another task. I tried the following, but well...i guess i miss some docu here.

l4_fpage_t fp = l4_fpage ( buffer, size, L4_FPAGE_RW); ioStream << fp;

Thanks again, ba_f