[Rcpp-devel] Resolving NativeSymbolInfos from Rcpp

Le 09/06/10 03:04, Davor Cubranic a ?crit :

Hi there,

I have a question about the murky world of R internals, DLLs, and
their interaction with Rcpp.

There are some C routines in the 'stats' package that I would like to
call directly from my Rcpp-based package, e.g., loess_raw. However,
'stats' only exposes them to R callers, not C or C++. (I.e., it does
not use R_RegisterCCallable, but they are among R_CMethodDef's passed
in R_registerRoutines.)

Reading the information on writing R extensions, it sounds like there
may not be a way to get to the address of an object in another
package's DLL. (In this case, in stats.so.) However, there is a
NativeSymbolInfo for stats:::R_loess_raw, which includes all sorts of
info about the C method. Is there a way that this can be used to get a
function pointer to it from within my code? And if this is too
unportable, is there a cleaner way?

Thanks,

Davor

Hi,

I see

 > getNativeSymbolInfo( "loess_raw" )

$name
[1] "loess_raw"

$address
<pointer: 0x103092820>
attr(,"class")
[1] "NativeSymbol"

$package
DLL name: stats
Filename:

/Library/Frameworks/R.framework/Resources/library/stats/libs/x86_64/stats.so

Dynamic lookup: FALSE

$numParameters
[1] 24

attr(,"class")
[1] "CRoutine" "NativeSymbolInfo"

So I'd probably look into the implementation of getNativeSymbolInfo
(R_getSymbol in file Rdynload.c) and figure out what sort of pointer is
the $address here. once you know that I suppose you can use it.

There is a good chance the pointer is a DL_FUNC. You probably want to
look at the Rdynpriv.h file too.

Maybe this question is more suited to R-devel.

Romain