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<p class=MsoNormal>I am a student of whatever the name “Erlang”
stands for – programming language, operating system, database system,
platform (whatever)!<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I am in a (mental) process of making NIF, and the two objects
in front of me are: <a href="http://www.erlang.org/doc/tutorial/nif.html">http://www.erlang.org/doc/tutorial/nif.html</a>
and <a href="http://www.erlang.org/doc/man/erl_nif.html">http://www.erlang.org/doc/man/erl_nif.html</a><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The NIF is meant for the private consumption of my
application, not to be exported for public. So, the pre & post conditions for
the NIF invocation are controlled. The onward and return payload for the NIF is
“binary”.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>By looking at the examples and the pattern of the set of
library functions in erl_nif, I (falsely) imagined that there would be
something like enif_get_binary() for receiving and enif_make_binary() for
returning, available in the library. While the latter was found and its
semantics for read-only (and memory release) understood from the documentation,
the former call, i.e. enif_get_binary(), was nowhere to be found.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Then, I found enif_get_string() – the progression of time
in the mental process is important here (at least, from a student’s point
of view). The thought did rise that perhaps I needed to pass a list of bytes (instead
of binary) to the NIF, but the last parameter, i.e. ErlNifCharEncoding, of
enif_get_string() stopped that thought, for I didn’t intend to encode the
bytes in ERL_NIF_LATIN1.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>So, I searched more, and found enif_inspect_binary() and
just below it the enif_is_binary() library function. For a moment, I doubted
why two calls for apparently same purpose – which is “gathered”
from the naming, only to find that the former, i.e. enif_inspect_binary(), not
only inspects but also initializes the ErlNifBinary structure, from where I
could pick up the payload and do the needful before calling enif_make_binary() at
the time of returning from NIF. I am still in a mental process, here.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>So, the question is: What considerations are needed, to
have, specifically for NIF and in general for Erlang, to appreciate the name
enif_inspect_binary() instead of enif_get_binary()? I suppose there are several
such “naming” places in Erlang, and I raised this particular one only
to give a play to the “why” urge in me.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks<o:p></o:p></p>
<p class=MsoNormal>Avinash<o:p></o:p></p>
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