memory.h

/**************************************************************************/
/*  memory.h                                                              */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#pragma once

#include "core/error/error_macros.h"
#include "core/templates/safe_refcount.h"

#include <new> // IWYU pragma: keep // `new` operators.
#include <type_traits>

class Memory {
#ifdef DEBUG_ENABLED
	static SafeNumeric<uint64_t> mem_usage;
	static SafeNumeric<uint64_t> max_usage;
#endif

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

	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)));

	template <bool p_ensure_zero = false>
	static void *alloc_static(size_t p_bytes, bool p_pad_align = false);
	_FORCE_INLINE_ static void *alloc_static_zeroed(size_t p_bytes, bool p_pad_align = false) { return alloc_static<true>(p_bytes, p_pad_align); }
	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);

	//	                            ↓ return value of alloc_aligned_static
	//	┌─────────────────┬─────────┬─────────┬──────────────────┐
	//	│ padding (up to  │ uint32_t│ void*   │ padding (up to   │
	//	│ p_alignment - 1)│ offset  │ p_bytes │ p_alignment - 1) │
	//	└─────────────────┴─────────┴─────────┴──────────────────┘
	//
	// alloc_aligned_static will allocate p_bytes + p_alignment - 1 + sizeof(uint32_t) and
	// then offset the pointer until alignment is satisfied.
	//
	// This offset is stored before the start of the returned ptr so we can retrieve the original/real
	// start of the ptr in order to free it.
	//
	// The rest is wasted as padding in the beginning and end of the ptr. The sum of padding at
	// both start and end of the block must add exactly to p_alignment - 1.
	//
	// p_alignment MUST be a power of 2.
	static void *alloc_aligned_static(size_t p_bytes, size_t p_alignment);
	static void *realloc_aligned_static(void *p_memory, size_t p_bytes, size_t p_prev_bytes, size_t p_alignment);
	// Pass the ptr returned by alloc_aligned_static to free it.
	// e.g.
	//	void *data = realloc_aligned_static( bytes, 16 );
	//  free_aligned_static( data );
	static void free_aligned_static(void *p_memory);

	static uint64_t get_mem_available();
	static uint64_t get_mem_usage();
	static uint64_t get_mem_max_usage();
};

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

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

#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

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

_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 memnew(m_class) _post_initialize(::new ("") m_class)

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

_ALWAYS_INLINE_ bool predelete_handler(void *) {
	return true;
}

template <typename T>
void memdelete(T *p_class) {
	if (!predelete_handler(p_class)) {
		return; // doesn't want to be deleted
	}
	if constexpr (!std::is_trivially_destructible_v<T>) {
		p_class->~T();
	}

	Memory::free_static(p_class, false);
}

template <typename T, typename A>
void memdelete_allocator(T *p_class) {
	if (!predelete_handler(p_class)) {
		return; // doesn't want to be deleted
	}
	if constexpr (!std::is_trivially_destructible_v<T>) {
		p_class->~T();
	}

	A::free(p_class);
}

#define memdelete_notnull(m_v) \
	{                          \
		if (m_v) {             \
			memdelete(m_v);    \
		}                      \
	}

#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) {
	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_constructible_v<T>) {
		T *elems = (T *)mem;

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

	return (T *)mem;
}

// Fast alternative to a loop constructor pattern.
template <typename T>
_FORCE_INLINE_ void memnew_arr_placement(T *p_start, size_t p_num) {
	if constexpr (is_zero_constructible_v<T>) {
		// Can optimize with memset.
		memset(static_cast<void *>(p_start), 0, p_num * sizeof(T));
	} else {
		// Need to use a for loop.
		for (size_t i = 0; i < p_num; i++) {
			memnew_placement(p_start + i, T());
		}
	}
}

/**
 * Wonders of having own array functions, you can actually check the length of
 * an allocated-with memnew_arr() array
 */

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 = nullptr;
	_GlobalNil *left = nullptr;
	_GlobalNil *parent = nullptr;

	_GlobalNil();
};

struct _GlobalNilClass {
	static _GlobalNil _nil;
};

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