//

// immer: immutable data structures for C++

// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente

//

// This software is distributed under the Boost Software License, Version 1.0.

// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt

//

#pragma once

#include <immer/config.hpp>

#include <immer/heap/tags.hpp>

#if IMMER_HAS_LIBGC

#include <gc/gc.h>

#else

#error "Using garbage collection requires libgc"

#endif

#include <cassert>

#include <cstdlib>

#include <exception>

#include <memory>

namespace immer {

#ifdef IMMER_GC_REQUIRE_INIT

#define IMMER_GC_REQUIRE_INIT_ IMMER_GC_REQUIRE_INIT

#elif defined __APPLE__

#define IMMER_GC_REQUIRE_INIT_ 1

#else

#define IMMER_GC_REQUIRE_INIT_ 0

#endif

#if IMMER_GC_REQUIRE_INIT_

namespace detail {

template <int Dummy = 0>

struct gc_initializer

{

    gc_initializer() { GC_INIT(); }

    static gc_initializer init;

};

template <int D>

gc_initializer<D> gc_initializer<D>::init{};

inline void gc_initializer_guard()

{

    static gc_initializer<> init_ = gc_initializer<>::init;

    (void) init_;

}

} // namespace detail

#define IMMER_GC_INIT_GUARD_ ::immer::detail::gc_initializer_guard()

#else

#define IMMER_GC_INIT_GUARD_

#endif // IMMER_GC_REQUIRE_INIT_

/*!

 * Heap that uses a tracing garbage collector.

 *

 * @rst

 *

 * This heap uses the `Boehm's conservative garbage collector`_ under

 * the hood.  This is a tracing garbage collector that automatically

 * reclaims unused memory.  Thus, it is not needed to call

 * ``deallocate()`` in order to release memory.

 *

 * .. admonition:: Dependencies

 *    :class: tip

 *

 *    In order to use this header file, you need to make sure that

 *    Boehm's ``libgc`` is your include path and link to its binary

 *    library.

 *

 * .. caution:: Memory that is allocated with the standard ``malloc``

 *    and ``free`` is not visible to ``libgc`` when it is looking for

 *    references.  This means that if, let's say, you store a

 *    :cpp:class:`immer::vector` using a ``gc_heap`` inside a

 *    ``std::vector`` that uses a standard allocator, the memory of

 *    the former might be released automatically at unexpected times

 *    causing crashes.

 *

 * .. caution:: When using a ``gc_heap`` in combination with immutable

 *    containers, the destructors of the contained objects will never

 *    be called.  It is ok to store containers inside containers as

 *    long as all of them use a ``gc_heap`` consistently, but storing

 *    other kinds of objects with relevant destructors

 *    (e.g. containers with reference counting or other kinds of

 *    *resource handles*) might cause memory leaks and other problems.

 *

 * .. _boehm's conservative garbage collector: https://github.com/ivmai/bdwgc

 *

 * @endrst

 */

class gc_heap

{

public:

    static void* allocate(std::size_t n)

    {

        IMMER_GC_INIT_GUARD_;

        auto p = GC_malloc(n);

        if (IMMER_UNLIKELY(!p))

            IMMER_THROW(std::bad_alloc{});

        return p;

    }

    static void* allocate(std::size_t n, norefs_tag)

    {

        IMMER_GC_INIT_GUARD_;

        auto p = GC_malloc_atomic(n);

        if (IMMER_UNLIKELY(!p))

            IMMER_THROW(std::bad_alloc{});

        return p;

    }

    static void deallocate(std::size_t, void* data) { GC_free(data); }

    static void deallocate(std::size_t, void* data, norefs_tag)

    {

        GC_free(data);

    }

};

} // namespace immer