--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/R/rdyncall/src/rutils.c	Thu Mar 19 22:26:28 2015 +0100
@@ -0,0 +1,40 @@
+/** ===========================================================================
+ ** R-Package: rdyncall
+ ** File: src/rutils.c
+ ** Description: misc utility functions to work with low-level data structures in R
+ **/
+
+// uses: DATAPTR macro
+#define USE_RINTERNALS
+#include <Rinternals.h>
+#include <stddef.h>
+
+SEXP r_isnullptr(SEXP x)
+{
+  return ScalarLogical( ( R_ExternalPtrAddr(x) == NULL ) ? TRUE : FALSE );
+}
+
+SEXP r_asextptr(SEXP x)
+{
+  if (isVector(x)) {
+    return R_MakeExternalPtr( DATAPTR(x), R_NilValue, x );
+  }
+  error("expected a vector type");
+  return R_NilValue; /* dummy */
+}
+
+SEXP r_offsetPtr(SEXP x, SEXP offset)
+{
+  if ( LENGTH(offset) == 0 ) error("offset is missing");
+  ptrdiff_t offsetval = INTEGER(offset)[0];
+  unsigned char* ptr = 0;
+  if (isVector(x)) {
+    ptr = (unsigned char*) DATAPTR(x);
+  } else if (TYPEOF(x) == EXTPTRSXP ) {
+    ptr = (unsigned char*) R_ExternalPtrAddr(x);
+  } else  {
+    error("unsupported type");
+  }
+  return R_MakeExternalPtr( ptr + offsetval , R_NilValue, x );
+}
+