[R-pkg-devel] How to pass a connection into a C function (R 3.2)

[Tom Quarendon]

So upshot is that I can only do why I want by using the function that's not part of the api, or just not using connections at all and just using normal C file io, opened from C, and simply pass the file name in instead, rather than a proper connection object?

> On 21 Jan 2016, at 6:04 pm, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
> 
>> On 21/01/2016 12:50 PM, Tom Quarendon wrote:
>> But that's what I want to do, create the connection in R code and pass it on to the C function.
>> My question is, how do I do that?
>> You appear to need the C getConnection entry point, but it's not part of the API.
>> So I'm wondering how I'm supposed to do what you describe.
> 
> Sorry, my advice was wrong.  I remembered that we exposed code to create new connections, and assumed it had some code to work with them, but it doesn't.
> 
> Duncan Murdoch
>> 
>> Sorry if I was unclear.
>> 
>> Sent from my iPhone
>> 
>> >> On 21 Jan 2016, at 5:44 pm, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
>> >>
>> >> On 21/01/2016 11:39 AM, Tom Quarendon wrote:
>> >> I would like to implement a package that contains a C function that writes to a connection.
>> >> So the R_ext/Connections.h defines what a connection IS, but not how to get one.
>> >>
>> >> What seems to work is to manually declare
>> >> Rconnection getConnection(int n);
>> >> In my C file, and while this works, and I can then use the connection object, it fails package validation with:
>> >>
>> >> �Found non-API call to R: �getConnection�
>> >> Compiled code should not call non-API entry points in R.�
>> >>
>> >> So how am I supposed to do this? Is there a way? Or do I just live with the check warning (ideally not)?
>> >
>> > The usual way to do that would be to create the connection in R code, and pass it in with your call.
>> >
>> > If you don't know what connection you need at the time you call your C code, you can evaluate an R expression from C to do the same, but this is relatively tricky, so I'd advise the other method.
>> >
>> > Duncan Murdoch
>