[Rd] defining r audio connections

Martin Morgan mtmorg@n@b|oc @end|ng |rom gm@||@com
Thu May 7 01:26:15 CEST 2020

yep, you're right, after some initial clean-up and running with or without --as-cran R CMD check gives a NOTE

  *  checking compiled code
  File ‘socketeer/libs/socketeer.so’:
    Found non-API calls to R: ‘R_GetConnection’,
  Compiled code should not call non-API entry points in R.
  See 'Writing portable packages' in the 'Writing R Extensions' manual.

Connections in general seem more useful than ad-hoc functions, though perhaps for Frederick's use case Duncan's suggestion is sufficient. For non-CRAN packages I personally would implement a connection.

(I mistakenly thought this was a more specialized mailing list; I wouldn't have posted to R-devel on this topic otherwise)

Martin Morgan

On 5/6/20, 4:12 PM, "Gábor Csárdi" <csardi.gabor using gmail.com> wrote:

    AFAIK that API is not allowed on CRAN. It triggers a NOTE or a
    WARNING, and your package will not be published.


    On Wed, May 6, 2020 at 9:04 PM Martin Morgan <mtmorgan.bioc using gmail.com> wrote:
    > The public connection API is defined in
    > https://github.com/wch/r-source/blob/trunk/src/include/R_ext/Connections.h
    > I'm not sure of a good pedagogic example; people who want to write their own connections usually want to do so for complicated reasons!
    > This is my own abandoned attempt https://github.com/mtmorgan/socketeer/blob/b0a1448191fe5f79a3f09d1f939e1e235a22cf11/src/connection.c#L169-L192 where connection_local_client() is called from R and _connection_local() creates and populates the appropriate structure. Probably I have done things totally wrong (e.g., by not checking the version of the API, as advised in the header file!)
    > Martin Morgan
    > On 5/6/20, 2:26 PM, "R-devel on behalf of Duncan Murdoch" <r-devel-bounces using r-project.org on behalf of murdoch.duncan using gmail.com> wrote:
    >     On 06/05/2020 1:09 p.m., frederik using ofb.net wrote:
    >     > Dear R Devel,
    >     >
    >     > Since Linux moved away from using a file-system interface for audio, I think it is necessary to write special libraries to interface with audio hardware from various languages on Linux.
    >     >
    >     > In R, it seems like the appropriate datatype for a `snd_pcm_t` handle pointing to an open ALSA source or sink would be a "connection". Connection types are already defined in R for "file", "url", "pipe", "fifo", "socketConnection", etc.
    >     >
    >     > Is there a tutorial or an example package where a new type of connection is defined, so that I can see how to do this properly in a package?
    >     >
    >     > I can see from the R source that, for example, `do_gzfile` is defined in `connections.c` and referenced in `names.c`. However, I thought I should ask here first in case there is a better place to start, than trying to copy this code.
    >     >
    >     > I only want an object that I can use `readBin` and `writeBin` on, to read and write audio data using e.g. `snd_pcm_writei` which is part of the `alsa-lib` package.
    >     I don't think R supports user-defined connections, but probably writing
    >     readBin and writeBin equivalents specific to your library wouldn't be
    >     any harder than creating a connection.  For those, you will probably
    >     want to work with an "external pointer" (see Writing R Extensions).
    >     Rcpp probably has support for these if you're working in C++.
    >     Duncan Murdoch
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