 the `userdata` argument contains a janet function the will be called with one argument, `ctx` which is an opaque pointer. This pointer can be further inspected with `ffi/read`.</pre><a href="https://janetdocs.org/ffi/trampoline">Community Examples</a></div><hr><div class="binding"><span id="ffi/write" class="binding-sym">ffi/write</span> <span class="binding-type">cfunction</span> <span class="binding-type"><a href="https://github.com/janet-lang/janet/blob/83e8aab/src/core/ffi.c#L1683">source</a></span> <p