godot-cpp/include/godot_cpp/core/memory.hpp

/**************************************************************************/
/*  memory.hpp                                                            */
/**************************************************************************/
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#ifndef GODOT_MEMORY_HPP
#define GODOT_MEMORY_HPP

#include <cstddef>
#include <cstdint>

#include <godot_cpp/core/defs.hpp>
#include <godot_cpp/core/error_macros.hpp>
#include <godot_cpp/godot.hpp>

#include <type_traits>

void *operator new(size_t p_size, const char *p_description); ///< operator new that takes a description and uses MemoryStaticPool
void *operator new(size_t p_size, void *(*p_allocfunc)(size_t p_size)); ///< operator new that takes a description and uses MemoryStaticPool
void *operator new(size_t p_size, void *p_pointer, size_t check, const char *p_description); ///< operator new that takes a description and uses a pointer to the preallocated memory

_ALWAYS_INLINE_ void *operator new(size_t p_size, void *p_pointer, size_t check, const char *p_description) {
	return p_pointer;
}

#ifdef _MSC_VER
// When compiling with VC++ 2017, the above declarations of placement new generate many irrelevant warnings (C4291).
// The purpose of the following definitions is to muffle these warnings, not to provide a usable implementation of placement delete.
void operator delete(void *p_mem, const char *p_description);
void operator delete(void *p_mem, void *(*p_allocfunc)(size_t p_size));
void operator delete(void *p_mem, void *p_pointer, size_t check, const char *p_description);
#endif

namespace godot {

class Wrapped;

class Memory {
	Memory();

public:
	// Alignment:  ↓ max_align_t        ↓ uint64_t          ↓ max_align_t
	//             ┌─────────────────┬──┬────────────────┬──┬───────────...
	//             │ uint64_t        │░░│ uint64_t       │░░│ T[]
	//             │ alloc size      │░░│ element count  │░░│ data
	//             └─────────────────┴──┴────────────────┴──┴───────────...
	// Offset:     ↑ SIZE_OFFSET        ↑ ELEMENT_OFFSET    ↑ DATA_OFFSET
	// Note: "alloc size" is used and set by the engine and is never accessed or changed for the extension.

	static constexpr size_t SIZE_OFFSET = 0;
	static constexpr size_t ELEMENT_OFFSET = ((SIZE_OFFSET + sizeof(uint64_t)) % alignof(uint64_t) == 0) ? (SIZE_OFFSET + sizeof(uint64_t)) : ((SIZE_OFFSET + sizeof(uint64_t)) + alignof(uint64_t) - ((SIZE_OFFSET + sizeof(uint64_t)) % alignof(uint64_t)));
	static constexpr size_t DATA_OFFSET = ((ELEMENT_OFFSET + sizeof(uint64_t)) % alignof(max_align_t) == 0) ? (ELEMENT_OFFSET + sizeof(uint64_t)) : ((ELEMENT_OFFSET + sizeof(uint64_t)) + alignof(max_align_t) - ((ELEMENT_OFFSET + sizeof(uint64_t)) % alignof(max_align_t)));

	static void *alloc_static(size_t p_bytes, bool p_pad_align = false);
	static void *realloc_static(void *p_memory, size_t p_bytes, bool p_pad_align = false);
	static void free_static(void *p_ptr, bool p_pad_align = false);
};

_ALWAYS_INLINE_ void postinitialize_handler(void *) {}

template <typename T>
_ALWAYS_INLINE_ T *_post_initialize(T *p_obj) {
	postinitialize_handler(p_obj);
	return p_obj;
}

#define memalloc(m_size) ::godot::Memory::alloc_static(m_size)
#define memrealloc(m_mem, m_size) ::godot::Memory::realloc_static(m_mem, m_size)
#define memfree(m_mem) ::godot::Memory::free_static(m_mem)

#define memnew(m_class) ::godot::_post_initialize(new ("") m_class)

#define memnew_allocator(m_class, m_allocator) ::godot::_post_initialize(new (m_allocator::alloc) m_class)
#define memnew_placement(m_placement, m_class) ::godot::_post_initialize(new (m_placement, sizeof(m_class), "") m_class)

// Generic comparator used in Map, List, etc.
template <typename T>
struct Comparator {
	_ALWAYS_INLINE_ bool operator()(const T &p_a, const T &p_b) const { return (p_a < p_b); }
};

template <typename T>
void memdelete(T *p_class, typename std::enable_if<!std::is_base_of_v<godot::Wrapped, T>>::type * = nullptr) {
	if constexpr (!std::is_trivially_destructible_v<T>) {
		p_class->~T();
	}

	Memory::free_static(p_class);
}

template <typename T, std::enable_if_t<std::is_base_of_v<godot::Wrapped, T>, bool> = true>
void memdelete(T *p_class) {
	godot::internal::gdextension_interface_object_destroy(p_class->_owner);
}

template <typename T, typename A>
void memdelete_allocator(T *p_class) {
	if constexpr (!std::is_trivially_destructible_v<T>) {
		p_class->~T();
	}

	A::free(p_class);
}

class DefaultAllocator {
public:
	_ALWAYS_INLINE_ static void *alloc(size_t p_memory) { return Memory::alloc_static(p_memory); }
	_ALWAYS_INLINE_ static void free(void *p_ptr) { Memory::free_static(p_ptr); }
};

template <typename T>
class DefaultTypedAllocator {
public:
	template <typename... Args>
	_ALWAYS_INLINE_ T *new_allocation(const Args &&...p_args) { return memnew(T(p_args...)); }
	_ALWAYS_INLINE_ void delete_allocation(T *p_allocation) { memdelete(p_allocation); }
};

#define memnew_arr(m_class, m_count) memnew_arr_template<m_class>(m_count)

_FORCE_INLINE_ uint64_t *_get_element_count_ptr(uint8_t *p_ptr) {
	return (uint64_t *)(p_ptr - Memory::DATA_OFFSET + Memory::ELEMENT_OFFSET);
}

template <typename T>
T *memnew_arr_template(size_t p_elements, const char *p_descr = "") {
	if (p_elements == 0) {
		return nullptr;
	}
	/** overloading operator new[] cannot be done , because it may not return the real allocated address (it may pad the 'element count' before the actual array). Because of that, it must be done by hand. This is the
	same strategy used by std::vector, and the Vector class, so it should be safe.*/

	size_t len = sizeof(T) * p_elements;
	uint8_t *mem = (uint8_t *)Memory::alloc_static(len, true);
	T *failptr = nullptr; // Get rid of a warning.
	ERR_FAIL_NULL_V(mem, failptr);

	uint64_t *_elem_count_ptr = _get_element_count_ptr(mem);
	*(_elem_count_ptr) = p_elements;

	if constexpr (!std::is_trivially_destructible_v<T>) {
		T *elems = (T *)mem;

		/* call operator new */
		for (size_t i = 0; i < p_elements; i++) {
			new (&elems[i], sizeof(T), p_descr) T;
		}
	}

	return (T *)mem;
}

template <typename T>
size_t memarr_len(const T *p_class) {
	uint8_t *ptr = (uint8_t *)p_class;
	uint64_t *_elem_count_ptr = _get_element_count_ptr(ptr);
	return *(_elem_count_ptr);
}

template <typename T>
void memdelete_arr(T *p_class) {
	uint8_t *ptr = (uint8_t *)p_class;

	if constexpr (!std::is_trivially_destructible_v<T>) {
		uint64_t *_elem_count_ptr = _get_element_count_ptr(ptr);
		uint64_t elem_count = *(_elem_count_ptr);

		for (uint64_t i = 0; i < elem_count; i++) {
			p_class[i].~T();
		}
	}

	Memory::free_static(ptr, true);
}

struct _GlobalNil {
	int color = 1;
	_GlobalNil *right;
	_GlobalNil *left;
	_GlobalNil *parent;

	_GlobalNil();
};

struct _GlobalNilClass {
	static _GlobalNil _nil;
};

} // namespace godot

#endif // GODOT_MEMORY_HPP