Le 09/06/10 07:14, Romain Francois a écrit :
Le 09/06/10 03:04, Davor Cubranic a écrit :
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 $address here. once you know that I suppose you can use it.
There is a good chance the pointer is a DL_FUNC. You probably want to
look at the Rdynpriv.h file too.
Maybe this question is more suited to R-devel.
Romain
After some more coffee, I came up with this:
require( Rcpp )
require( inline )
# borrowed from R private headers
# not part of R API, but does not change all that much
include <- '
typedef union {void *p; DL_FUNC fn;} fn_ptr;
DL_FUNC R_ExternalPtrAddrFn(SEXP s){
fn_ptr tmp;
tmp.p = EXTPTR_PTR(s);
return tmp.fn;
}
'
code <- '
// grab loess_raw
DL_FUNC loess_raw = R_ExternalPtrAddrFn( xp ) ;
Rprintf( "loess_raw : <%p>\\n", loess_raw ) ;
// call it
// (*loess_raw)( ... )
return R_NilValue ;
'
fx <- cxxfunction( signature( xp = "externalptr" ),
code, include = include, plugin = "Rcpp" )
fx( getNativeSymbolInfo( "loess_raw" )$address )
Please expand the part that is actually suppose to call loess_raw and
let us know if something useful happens.
It might be worth formalize that sort of things in a nice Rcpp
abstraction. For example, make a Rcpp::DynamicLibrary class with member
functions to pull these things conveniently.
Romain
--
Romain Francois
Professional R Enthusiast
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http://romainfrancois.blog.free.fr
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