On 8 December 2014 at 09:58, Tim Keitt wrote:
|
|
| On Sun, Dec 7, 2014 at 4:52 AM, Dirk Eddelbuettel <e...@debian.org> wrote:
|
|
|
| What you are after, if I understand it correctly, is (close to) a common
| and
| well studied idiom called 'RAII': Resource Acquisition is Initialization.
| Two
| quick links, and you will find many more:
|
|
|
| I don't know if this example is helpful. Any class that can be initialized
with
| an SEXP and has an SEXP member function can be used as the argument or return
| type from an Rcpp function call. I wrote this wrapper to avoid dereferencing
| passed null pointers and as a return type for a lot of functions where I want
| an R NULL return if the pointer is null.
Nice post for the r-devel list :) But as you don't use Rcpp here...
In essence Rcpp::XPtr does this for you. If you rewrote the code in terms of
Rcpp::XPtr, it might make for a nice post for the Rcpp Gallery.
Dirk
| THK
|
|
| class
| RGDALHandleWrapper
| {
| public:
| RGDALHandleWrapper(void* h)
| : handle(h) {} // If initialized NULL will return NULL
| SEXP
| RGDALHandleWrapper(const SEXP h)
| : handle(R_ExternalPtrAddr(h))
| {
| if ( !handle ) stop("Null pointer passed to
function\n"
| );
| }
| operator SEXP() const
| {
| return handle ? // Return NULL SEXP on NULL pointer
| R_MakeExternalPtr(handle, R_NilValue, R_NilValue) :
| R_NilValue;
| }
| void* operator*() const { return handle; }
| private:
| void* handle;
| };
|
|
|
|
| --
| http://www.keittlab.org/
--
http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
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