Adding nameof utility function

cpp11test/src/cpp11.cpp

@@ -5,6 +5,7 @@
 #include <Rcpp.h>
 using namespace Rcpp;
 #include "cpp11/declarations.hpp"
+#include <R_ext/Visibility.h>
 
 // add.cpp
 SEXP cpp11_add_vec_for_(cpp11::writable::doubles x, double num);
@@ -444,7 +445,7 @@ static const R_CallMethodDef CallEntries[] = {
 };
 }
 
-extern "C" void R_init_cpp11test(DllInfo* dll){
+extern "C" attribute_visible void R_init_cpp11test(DllInfo* dll){
   R_registerRoutines(dll, NULL, CallEntries, NULL, NULL);
   R_useDynamicSymbols(dll, FALSE);
   R_forceSymbols(dll, TRUE);

cpp11test/src/test-nameof.cpp

@@ -0,0 +1,21 @@
+#include "cpp11/nameof.hpp"
+
+#include <testthat.h>
+
+struct Global;
+
+namespace ns {
+struct Namespaced;
+}  // namespace ns
+
+context("nameof-C++") {
+  test_that("nameof works") {
+    expect_true(cpp11::nameof<Global>() == "Global");
+    expect_true(cpp11::nameof<ns::Namespaced>() == "ns::Namespaced");
+    expect_true(cpp11::nameof<ns::Namespaced>(/*strip_namespace=*/true) == "Namespaced");
+
+    // namespace for local scope structs is compiler dependent
+    struct Local;
+    expect_true(cpp11::nameof<Local>(/*strip_namespace=*/true) == "Local");
+  }
+}

inst/include/cpp11/nameof.hpp

@@ -0,0 +1,82 @@
+/// Distributed under the Boost Software License, Version 1.0. (See
+/// http://www.boost.org/LICENSE_1_0.txt)
+
+#include <array>
+#include <string>
+#include <tuple>
+#include <utility>
+
+namespace cpp11 {
+namespace detail {
+
+#ifdef _MSC_VER
+#define ARROW_PRETTY_FUNCTION __FUNCSIG__
+#else
+#define ARROW_PRETTY_FUNCTION __PRETTY_FUNCTION__
+#endif
+
+template <typename T>
+const char* raw() {
+  return ARROW_PRETTY_FUNCTION;
+}
+
+template <typename T>
+size_t raw_sizeof() {
+  return sizeof(ARROW_PRETTY_FUNCTION);
+}
+
+#undef ARROW_PRETTY_FUNCTION
+
+constexpr bool starts_with(char const* haystack, char const* needle) {
+  return needle[0] == '\0' ||
+         (haystack[0] == needle[0] && starts_with(haystack + 1, needle + 1));
+}
+
+constexpr size_t search(char const* haystack, char const* needle) {
+  return haystack[0] == '\0' || starts_with(haystack, needle)
+             ? 0
+             : search(haystack + 1, needle) + 1;
+}
+
+const size_t typename_prefix = search(raw<double>(), "double");
+
+template <typename T>
+size_t struct_class_prefix() {
+#ifdef _MSC_VER
+  return starts_with(raw<T>() + typename_prefix, "struct ")
+             ? 7
+             : starts_with(raw<T>() + typename_prefix, "class ") ? 6 : 0;
+#else
+  return 0;
+#endif
+}
+
+template <typename T>
+size_t typename_length() {
+  // raw_sizeof<T>() - raw_sizeof<double>() ==
+  //     (length of T's name) - strlen("double")
+  // (length of T's name) ==
+  //     raw_sizeof<T>() - raw_sizeof<double>() + strlen("double")
+  return raw_sizeof<T>() - struct_class_prefix<T>() - raw_sizeof<double>() + 6;
+}
+
+template <typename T>
+const char* typename_begin() {
+  return raw<T>() + struct_class_prefix<T>() + typename_prefix;
+}
+
+}  // namespace detail
+
+template <typename T>
+std::string nameof(bool strip_namespace = false) {
+  std::string name{detail::typename_begin<T>(), detail::typename_length<T>()};
+  if (strip_namespace) {
+    auto i = name.find_last_of("::");
+    if (i != std::string::npos) {
+      name = name.substr(i + 1);
+    }
+  }
+  return name;
+}
+
+}  // namespace cpp11