#77 started incorporating bobs C++ code for the roundtrip work around

DESCRIPTION

@@ -15,12 +15,15 @@ URL: https://github.com/ropensci/geojsonio
 BugReports: http://www.github.com/ropensci/geojsonio/issues
 LazyData: true
 VignetteBuilder: knitr
+LinkingTo: 
+    Rcpp (>= 0.12.0)
 Depends:
-    R (>= 2.10)
+    R (>= 3.02)
 Imports:
     methods,
     stats,
     utils,
+    Rcpp (>= 0.12.3),
     sp,
     rgdal,
     rgeos,

NAMESPACE

@@ -165,6 +165,7 @@ export(validate)
 import(methods)
 import(rgeos)
 import(sp)
+importFrom(Rcpp,evalCpp)
 importFrom(V8,new_context)
 importFrom(httr,GET)
 importFrom(httr,POST)
@@ -182,3 +183,4 @@ importFrom(rgdal,readOGR)
 importFrom(rgdal,writeOGR)
 importFrom(stats,setNames)
 importFrom(utils,download.file)
+useDynLib(geojsonio)

R/RcppExports.R

@@ -0,0 +1,20 @@
+# This file was generated by Rcpp::compileAttributes
+# Generator token: 10BE3573-1514-4C36-9D1C-5A225CD40393
+
+#' An \code{writeOGR} shim to capture stdout
+#'
+#' @param obj the \code{Spatial} object to use
+#' @param obj_size pls pass in \code{object.size(obj)}
+#' @param layer spatial layer to use
+#' @param writeOGR pls pass in \code{writeOGR} (no quotes)
+#' @return character vector of GeoJSON if all goes well
+#' @examples \dontrun{
+#' capturedWriteOGR(cities[1:10,],
+#'                  object.size(cities[1:10,]),
+#'                  "cities",
+#'                  writeOGR))
+#' }
+capturedWriteOGR <- function(obj, obj_size, layer, writeOGR) {
+    .Call('geojsonio_capturedWriteOGR', PACKAGE = 'geojsonio', obj, obj_size, layer, writeOGR)
+}
+

R/geojsonio-package.r

@@ -42,6 +42,8 @@
 #' @importFrom maptools readShapeSpatial
 #' @importFrom rgdal readOGR writeOGR ogrListLayers
 #' @importFrom magrittr %>%
+#' @importFrom Rcpp evalCpp
+#' @useDynLib geojsonio
 #' @name geojsonio
 #' @author Scott Chamberlain \email{myrmecocystus@@gmail.com}
 #' @author Andy Teucher \email{andy.teucher@@gmail.com}

src/RcppExports.cpp

@@ -0,0 +1,21 @@
+// This file was generated by Rcpp::compileAttributes
+// Generator token: 10BE3573-1514-4C36-9D1C-5A225CD40393
+
+#include <Rcpp.h>
+
+using namespace Rcpp;
+
+// capturedWriteOGR
+CharacterVector capturedWriteOGR(SEXP obj, int obj_size, SEXP layer, Function writeOGR);
+RcppExport SEXP geojsonio_capturedWriteOGR(SEXP objSEXP, SEXP obj_sizeSEXP, SEXP layerSEXP, SEXP writeOGRSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject __result;
+    Rcpp::RNGScope __rngScope;
+    Rcpp::traits::input_parameter< SEXP >::type obj(objSEXP);
+    Rcpp::traits::input_parameter< int >::type obj_size(obj_sizeSEXP);
+    Rcpp::traits::input_parameter< SEXP >::type layer(layerSEXP);
+    Rcpp::traits::input_parameter< Function >::type writeOGR(writeOGRSEXP);
+    __result = Rcpp::wrap(capturedWriteOGR(obj, obj_size, layer, writeOGR));
+    return __result;
+END_RCPP
+}

src/captured_write_ogr.cpp

@@ -0,0 +1,82 @@
+#include <Rcpp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+using namespace Rcpp;
+
+//' An \code{writeOGR} shim to capture stdout
+//'
+//' @param obj the \code{Spatial} object to use
+//' @param obj_size pls pass in \code{object.size(obj)}
+//' @param layer spatial layer to use
+//' @param writeOGR pls pass in \code{writeOGR} (no quotes)
+//' @return character vector of GeoJSON if all goes well
+//' @examples \dontrun{
+//' capturedWriteOGR(cities[1:10,],
+//'                  object.size(cities[1:10,]),
+//'                  "cities",
+//'                  writeOGR))
+//' }
+// [[Rcpp::export]]
+CharacterVector capturedWriteOGR(SEXP obj,
+                                 int obj_size,
+                                 SEXP layer,
+                                 Function writeOGR) {
+
+  // we don't know how big the output is going to be.
+  // this is the main problem with this approach.
+  // there is no error checking yet
+  // i have no idea if this works on Windows
+  // this was a hack on a commuter train ;-)
+
+  // this could cause us to run out of memory
+  // we need checking for sizes, mem avail and errors
+
+  // allocate a buffer to hold the output geojson
+  // and initialize it so we's sure to have a null term'd string
+  int MAX_LEN = obj_size * 10 ;
+  char buffer[MAX_LEN+1];
+  memset(buffer, 0, sizeof (char) * (MAX_LEN+1));
+
+  // now we're going to mess with pipes. the way the VSI stuff
+  // mangles stdout in gdal means that we can't use nice C++
+  // redirects and have to resort to file descriptor hacking
+
+  int out_pipe[2];
+  int saved_stdout;
+
+  saved_stdout = dup(STDOUT_FILENO);
+
+  // ok, there's some error checking if we couldn't even
+  // get the hack started
+
+  if (pipe(out_pipe) != 0 ) { return(NA_STRING); }
+
+  dup2(out_pipe[1], STDOUT_FILENO);
+  close(out_pipe[1]);
+
+  // we've setup the capture, so let writeOGR do it's thing
+  // we are calling R from C since the rgdal folks have not
+  // exposed anything we can use AFAI can tell
+
+  writeOGR(obj, "/vsistdout/", layer, "GeoJSON");
+
+  // ok, we let it do it's thing, now make sure we've
+  // cleatned up after it
+
+  fflush(stdout);
+
+  // now, get that mess into somet hign we can use
+
+  read(out_pipe[0], buffer, MAX_LEN);
+
+  // restore order to the universe
+
+  dup2(saved_stdout, STDOUT_FILENO);
+
+  // say a little prayer
+
+  return(wrap(buffer));
+
+}