enum.hpp

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#pragma once
 
#include <algorithm>
#include <cassert>
#include <string>
#include <optional>
 
namespace mbgl {
 
template <typename T>
class Enum {
public:
    using Type = T;
    static const char * toString(T);
    static std::optional<T> toEnum(const std::string&);
};
 
#define MBGL_DEFINE_ENUM(T, ...)                                                   \
                                                                                   \
static const constexpr std::pair<const T, const char *> T##_names[] = __VA_ARGS__; \
                                                                                   \
template <>                                                                        \
const char * Enum<T>::toString(T t) {                                              \
    auto it = std::find_if(std::begin(T##_names), std::end(T##_names),             \
        [&] (const auto& v) { return t == v.first; });                             \
    assert(it != std::end(T##_names)); return it->second;                          \
}                                                                                  \
                                                                                   \
template <>                                                                        \
std::optional<T> Enum<T>::toEnum(const std::string& s) {                                \
    auto it = std::find_if(std::begin(T##_names), std::end(T##_names),             \
        [&] (const auto& v) { return s == v.second; });                            \
    return it == std::end(T##_names) ? std::optional<T>() : it->first;                  \
}
 
} // namespace mbgl