sol2/sol/reference.hpp

// The MIT License (MIT) 

// Copyright (c) 2013-2016 Rapptz, ThePhD and contributors

// 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 SOL_REFERENCE_HPP
#define SOL_REFERENCE_HPP

#include "types.hpp"
#include "stack_reference.hpp"

namespace sol {
namespace stack {
template <bool top_level, typename T>
struct push_popper {
    T t;
    push_popper (T x) : t(x) { t.push(); }
    ~push_popper() { t.pop(); }
};
template <typename T>
struct push_popper<true, T> {
    push_popper (T) {}
    ~push_popper() {}
};
template <bool top_level = false, typename T>
push_popper<top_level, T> push_pop(T&& x) {
    return push_popper<top_level, T>(std::forward<T>(x));
}
} // stack

namespace detail {
struct global_tag { } const global_{};
} // detail

class reference {
private:
    lua_State* L = nullptr; // non-owning
    int ref = LUA_NOREF;

    int copy() const noexcept {
        if (ref == LUA_NOREF)
            return LUA_NOREF;
        push();
        return luaL_ref(L, LUA_REGISTRYINDEX);
    }

protected:
    reference(lua_State* L, detail::global_tag) noexcept : L(L) {
        lua_pushglobaltable(L);
        ref = luaL_ref(L, LUA_REGISTRYINDEX);
    }

    int stack_index() const noexcept {
        return -1;
    }

public:
    reference() noexcept = default;
    reference(const stack_reference& r) noexcept : reference(r.lua_state(), r.stack_index()) {}
    reference(stack_reference&& r) noexcept : reference(r.lua_state(), r.stack_index()) {}
    reference(lua_State* L, int index = -1) noexcept : L(L) {
        lua_pushvalue(L, index);
        ref = luaL_ref(L, LUA_REGISTRYINDEX);
    }

    virtual ~reference() noexcept {
        luaL_unref(L, LUA_REGISTRYINDEX, ref);
    }

    reference(reference&& o) noexcept {
        L = o.L;
        ref = o.ref;

        o.L = nullptr;
        o.ref = LUA_NOREF;
    }

    reference& operator=(reference&& o) noexcept {
        L = o.L;
        ref = o.ref;

        o.L = nullptr;
        o.ref = LUA_NOREF;

        return *this;
    }

    reference(const reference& o) noexcept {
        L = o.L;
        ref = o.copy();
    }

    reference& operator=(const reference& o) noexcept {
        L = o.L;
        ref = o.copy();
        return *this;
    }

    int push() const noexcept {
        lua_rawgeti(L, LUA_REGISTRYINDEX, ref);
        return 1;
    }

    void pop(int n = 1) const noexcept {
        lua_pop(lua_state( ), n);
    }

    int registry_index() const noexcept {
        return ref;
    }

    bool valid () const noexcept {
        return !(ref == LUA_NOREF || ref == LUA_REFNIL);
    }

    explicit operator bool () const noexcept {
        return valid();
    }

    type get_type() const noexcept {
        push();
        int result = lua_type(L, -1);
        lua_pop(L, 1);
        return static_cast<type>(result);
    }

    lua_State* lua_state() const noexcept {
        return L;
    }
};

inline bool operator== (const reference& l, const reference& r) {
    auto ppl = stack::push_pop(l);
    auto ppr = stack::push_pop(r);
    return lua_compare(l.lua_state(), -1, -2, LUA_OPEQ) == 1;
}

inline bool operator!= (const reference& l, const reference& r) {
    return !operator==(l, r);
}
} // sol

#endif // SOL_REFERENCE_HPP