r/src/nameof.h

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#include <string>

namespace arrow {
namespace util {
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 util
}  // namespace arrow