type_name.hpp

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// Copyright (C) 2020-2023 Jonathan Müller and lexy contributors
// SPDX-License-Identifier: BSL-1.0
 
#ifndef LEXY_DETAIL_TYPE_NAME_HPP_INCLUDED
#define LEXY_DETAIL_TYPE_NAME_HPP_INCLUDED
 
#include <lexy/_detail/config.hpp>
#include <lexy/_detail/detect.hpp>
#include <lexy/_detail/integer_sequence.hpp>
#include <lexy/_detail/string_view.hpp>
 
namespace lexy::_detail
{
template <typename T>
using _detect_name_f = std::enable_if_t<std::is_convertible_v<decltype(T::name()), string_view>>;
template <typename T>
using _detect_name_v = decltype(T::name);
 
template <typename T>
constexpr auto _full_type_name()
{
#if defined(__clang__)
#    define LEXY_HAS_AUTOMATIC_TYPE_NAME 1
#    define LEXY_HAS_CONSTEXPR_AUTOMATIC_TYPE_NAME 1
 
    constexpr auto prefix = string_view("auto lexy::_detail::_full_type_name() [T = ");
    constexpr auto suffix = string_view("]");
 
    auto function = string_view(__PRETTY_FUNCTION__);
    function.remove_prefix(prefix.length());
    function.remove_suffix(suffix.length());
    return function;
 
#elif defined(__GNUC__)
#    define LEXY_HAS_AUTOMATIC_TYPE_NAME 1
#    if __GNUC__ > 8
#        define LEXY_HAS_CONSTEXPR_AUTOMATIC_TYPE_NAME 1
#    else
#        define LEXY_HAS_CONSTEXPR_AUTOMATIC_TYPE_NAME 0
#    endif
 
    constexpr auto prefix
        = string_view("constexpr auto lexy::_detail::_full_type_name() [with T = ");
    constexpr auto suffix = string_view("]");
 
    auto function = string_view(__PRETTY_FUNCTION__);
    function.remove_prefix(prefix.length());
    function.remove_suffix(suffix.length());
    return function;
 
#elif defined(_MSC_VER)
#    define LEXY_HAS_AUTOMATIC_TYPE_NAME 1
#    define LEXY_HAS_CONSTEXPR_AUTOMATIC_TYPE_NAME 1
 
    constexpr auto prefix = string_view("auto __cdecl lexy::_detail::_full_type_name<");
    constexpr auto suffix = string_view(">(void)");
 
    auto function = string_view(__FUNCSIG__);
    function.remove_prefix(prefix.length());
    function.remove_suffix(suffix.length());
 
    if (auto s = string_view("struct "); function.starts_with(s))
        function.remove_prefix(s.length());
    else if (auto c = string_view("class "); function.starts_with(c))
        function.remove_prefix(c.length());
 
    return function;
 
#else
#    define LEXY_HAS_AUTOMATIC_TYPE_NAME 0
#    define LEXY_HAS_CONSTEXPR_AUTOMATIC_TYPE_NAME 0
 
    return string_view("unknown-type");
 
#endif
}
 
template <typename T, int NsCount>
constexpr string_view _type_name()
{
    auto name = _full_type_name<T>();
    if (name.find('<') != string_view::npos && NsCount != 0)
        return name;
 
    for (auto namespace_count = NsCount; namespace_count > 0; --namespace_count)
    {
        auto pos = name.find("::");
        if (pos == string_view::npos)
            break;
        name.remove_prefix(pos + 2);
    }
    return name;
}
 
template <typename T, int NsCount = 1>
constexpr const char* type_name()
{
    if constexpr (_detail::is_detected<_detect_name_f, T>)
        return T::name();
    else if constexpr (_detail::is_detected<_detect_name_v, T>)
        return T::name;
    else if constexpr (LEXY_HAS_CONSTEXPR_AUTOMATIC_TYPE_NAME)
        return make_cstr<_type_name<T, NsCount>>;
    else
        return "unknown-type";
}
 
template <typename T, int NsCount>
inline constexpr const char* _type_id_holder = type_name<T, NsCount>();
 
// Returns a unique address for each type.
// For implementation reasons, it also doubles as the pointer to the name.
template <typename T, int NsCount = 1>
constexpr const char* const* type_id()
{
    if constexpr (_detail::is_detected<_detect_name_v, T> //
                  && !_detail::is_detected<_detect_name_f, T>)
    {
        // We can use the address of the static constexpr directly.
        return &T::name;
    }
    else
    {
        // We instantiate a variable template with a function unique by type.
        // As the variable is inline, there should be a single address only.
        return &_type_id_holder<T, NsCount>;
    }
}
} // namespace lexy::_detail
 
#endif // LEXY_DETAIL_TYPE_NAME_HPP_INCLUDED