use namespace & not fix return

converters.h

@@ -0,0 +1,105 @@
+#ifndef MRUBYPP_STD_CONVERTERS_H
+#define MRUBYPP_STD_CONVERTERS_H
+
+#include "arena_guard.h"
+
+#include <mruby.h>
+#include <mruby/array.h>
+#include <mruby/string.h>
+#include <string>
+#include <vector>
+
+namespace mrubypp {
+
+template <typename T> struct converter {
+  static mrb_value to_mrb(mrb_state *mrb, const T &var) {
+    static_assert(sizeof(T) == 0, "Specialization required");
+    return mrb_nil_value();
+  }
+  static T from_mrb(mrb_state *mrb, mrb_value value) {
+    static_assert(sizeof(T) == 0, "Specialization required");
+    return T();
+  }
+};
+
+template <> struct converter<int> {
+  static mrb_value to_mrb(mrb_state *mrb, int var) {
+    return mrb_fixnum_value(var);
+  }
+  static int from_mrb(mrb_state *mrb, mrb_value value) {
+    return mrb_fixnum(value);
+  }
+};
+
+template <> struct converter<unsigned int> {
+  static mrb_value to_mrb(mrb_state *mrb, unsigned int var) {
+    return mrb_fixnum_value(var);
+  }
+  static int from_mrb(mrb_state *mrb, mrb_value value) {
+    return mrb_fixnum(value);
+  }
+};
+
+template <> struct converter<float> {
+  static mrb_value to_mrb(mrb_state *mrb, float var) {
+    return mrb_float_value(mrb, var);
+  }
+  static double from_mrb(mrb_state *mrb, mrb_value value) {
+    return mrb_float(value);
+  }
+};
+
+template <> struct converter<double> {
+  static mrb_value to_mrb(mrb_state *mrb, double var) {
+    return mrb_float_value(mrb, var);
+  }
+  static double from_mrb(mrb_state *mrb, mrb_value value) {
+    return mrb_float(value);
+  }
+};
+
+template <> struct converter<std::string> {
+  static mrb_value to_mrb(mrb_state *mrb, const std::string &var) {
+    return mrb_str_new(mrb, var.data(), (mrb_int)var.size());
+  }
+
+  static std::string from_mrb(mrb_state *mrb, mrb_value value) {
+    if (mrb_string_p(value)) {
+      return std::string(RSTRING_PTR(value), RSTRING_LEN(value));
+    }
+    return {};
+  }
+};
+
+template <> struct converter<const char *> {
+  static mrb_value to_mrb(mrb_state *mrb, const char *var) {
+    return mrb_str_new(mrb, var, (mrb_int)strlen(var));
+  }
+};
+
+template <typename T> struct converter<std::vector<T>> {
+  static mrb_value to_mrb(mrb_state *mrb, const std::vector<T> &var) {
+    mrb_value ary = mrb_ary_new_capa(mrb, static_cast<mrb_int>(var.size()));
+    for (const T &el : var) {
+      arena_guard guard(mrb);
+      mrb_ary_push(mrb, ary, converter<T>::to_mrb(mrb, el));
+    }
+    return ary;
+  }
+
+  static std::vector<T> from_mrb(mrb_state *mrb, mrb_value value) {
+    arena_guard guard(mrb);
+    std::vector<T> result;
+    if (mrb_array_p(value)) {
+      int len = RARRAY_LEN(value);
+      for (int i = 0; i < len; ++i) {
+        result.append(converter<T>::from_mrb(mrb, mrb_ary_ref(mrb, value, i)));
+      }
+    }
+    return result;
+  }
+};
+
+} // namespace mrubypp
+
+#endif // MRUBYPP_STD_CONVERTERS_H