// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors // Licensed under the MIT License: // // Permission is hereby granted, free of charge, to any person obtaining a copy // of this software and associated documentation files (the "Software"), to deal // in the Software without restriction, including without limitation the rights // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell // copies of the Software, and to permit persons to whom the Software is // furnished to do so, subject to the following conditions: // // The above copyright notice and this permission notice shall be included in // all copies or substantial portions of the Software. // // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN // THE SOFTWARE. #ifndef KJ_ONE_OF_H_ #define KJ_ONE_OF_H_ #if defined(__GNUC__) && !KJ_HEADER_WARNINGS #pragma GCC system_header #endif #include "common.h" namespace kj { namespace _ { // private template <uint i, typename Key, typename First, typename... Rest> struct TypeIndex_ { static constexpr uint value = TypeIndex_<i + 1, Key, Rest...>::value; }; template <uint i, typename Key, typename... Rest> struct TypeIndex_<i, Key, Key, Rest...> { static constexpr uint value = i; }; } // namespace _ (private) template <typename... Variants> class OneOf { template <typename Key> static inline constexpr uint typeIndex() { return _::TypeIndex_<1, Key, Variants...>::value; } // Get the 1-based index of Key within the type list Types. public: inline OneOf(): tag(0) {} OneOf(const OneOf& other) { copyFrom(other); } OneOf(OneOf&& other) { moveFrom(other); } ~OneOf() { destroy(); } OneOf& operator=(const OneOf& other) { if (tag != 0) destroy(); copyFrom(other); return *this; } OneOf& operator=(OneOf&& other) { if (tag != 0) destroy(); moveFrom(other); return *this; } inline bool operator==(decltype(nullptr)) const { return tag == 0; } inline bool operator!=(decltype(nullptr)) const { return tag != 0; } template <typename T> bool is() const { return tag == typeIndex<T>(); } template <typename T> T& get() { KJ_IREQUIRE(is<T>(), "Must check OneOf::is<T>() before calling get<T>()."); return *reinterpret_cast<T*>(space); } template <typename T> const T& get() const { KJ_IREQUIRE(is<T>(), "Must check OneOf::is<T>() before calling get<T>()."); return *reinterpret_cast<const T*>(space); } template <typename T, typename... Params> void init(Params&&... params) { if (tag != 0) destroy(); ctor(*reinterpret_cast<T*>(space), kj::fwd<Params>(params)...); tag = typeIndex<T>(); } private: uint tag; static inline constexpr size_t maxSize(size_t a) { return a; } template <typename... Rest> static inline constexpr size_t maxSize(size_t a, size_t b, Rest... rest) { return maxSize(kj::max(a, b), rest...); } // Returns the maximum of all the parameters. // TODO(someday): Generalize the above template and make it common. I tried, but C++ decided to // be difficult so I cut my losses. union { byte space[maxSize(sizeof(Variants)...)]; void* forceAligned; // TODO(someday): Use C++11 alignas() once we require GCC 4.8 / Clang 3.3. }; template <typename... T> inline void doAll(T... t) {} template <typename T> inline bool destroyVariant() { if (tag == typeIndex<T>()) { tag = 0; dtor(*reinterpret_cast<T*>(space)); } return false; } void destroy() { doAll(destroyVariant<Variants>()...); } template <typename T> inline bool copyVariantFrom(const OneOf& other) { if (other.is<T>()) { ctor(*reinterpret_cast<T*>(space), other.get<T>()); } return false; } void copyFrom(const OneOf& other) { // Initialize as a copy of `other`. Expects that `this` starts out uninitialized, so the tag // is invalid. tag = other.tag; doAll(copyVariantFrom<Variants>(other)...); } template <typename T> inline bool moveVariantFrom(OneOf& other) { if (other.is<T>()) { ctor(*reinterpret_cast<T*>(space), kj::mv(other.get<T>())); } return false; } void moveFrom(OneOf& other) { // Initialize as a copy of `other`. Expects that `this` starts out uninitialized, so the tag // is invalid. tag = other.tag; doAll(moveVariantFrom<Variants>(other)...); } }; } // namespace kj #endif // KJ_ONE_OF_H_