On Jun 12, 9:24 pm, Wayne Meissner <wmeiss...@gmail.com> wrote:

> A couple of things:
> 1) You should map getprotobynumber_r as:
>
> attach_function 'getprotobynumber_r', [:int, :pointer, :pointer,
> :long, :pointer], :int
>
> 2) and call it like so:
>
> # getprotobynumber_r will use the buffer you pass in as the allocation
> area for the names
> # of the protocol, so allocate some native memory for it.
>
> namebuf  = FFI::MemoryPointer.new(:char, 1024, false)
> pstruct = ProtocolStruct.new
> ptr = FFI::MemoryPointer.new(:pointer)
>
> rc = getprotobynumber_r(protocol, pstruct, namebuf, 1024, qptr)
>
> 3) a return val of 0 signifies success, and pstruct will be filled out
> with the data.  For non-zero returns, you should probably check errno,
> and raise an exception if it is anything other than the not-found
> case.
>
> return rc == 0 && !qptr.get_pointer(0).null? ? pstruct[:p_name] : nil

Excellent, thanks!

Dan