Double-buffered frame allocator. More...

#include <double_frame_allocator.hpp>

Public Member Functions
	DoubleFrameAllocator (size_t capacity_per_buffer)
	Constructs a double frame allocator with specified capacity per buffer.

	DoubleFrameAllocator (const DoubleFrameAllocator &)=delete

	DoubleFrameAllocator (DoubleFrameAllocator &&other) noexcept

	~DoubleFrameAllocator () noexcept=default

DoubleFrameAllocator &	operator= (const DoubleFrameAllocator &)=delete

DoubleFrameAllocator &	operator= (DoubleFrameAllocator &&other) noexcept

AllocationResult	Allocate (size_t size, size_t alignment=kDefaultAlignment) noexcept
	Allocates memory from the current frame buffer.

template<typename T >
T *	Allocate () noexcept
	Allocates memory for a single object of type T.

template<typename T >
T *	Allocate (size_t count) noexcept
	Allocates memory for an array of objects of type T.

template<typename T , typename... Args> requires std::constructible_from<T, Args...>
T *	AllocateAndConstruct (Args &&... args) noexcept(std::is_nothrow_constructible_v< T, Args... >)
	Allocates and constructs a single object of type T.

template<typename T > requires std::default_initializable<T>
T *	AllocateAndConstructArray (size_t count) noexcept(std::is_nothrow_default_constructible_v< T >)
	Allocates and default-constructs an array of objects of type T.

void	NextFrame () noexcept
	Advances to the next frame, switching buffers.

void	Reset () noexcept
	Resets both buffers.

AllocatorStats	Stats () const noexcept
	Gets combined statistics for both buffers.

AllocatorStats	CurrentFrameStats () const noexcept
	Gets statistics for the current frame buffer.

AllocatorStats	PreviousFrameStats () const noexcept
	Gets statistics for the previous frame buffer.

size_t	Capacity () const noexcept
	Gets the total capacity across both buffers.

size_t	CurrentBufferIndex () const noexcept
	Gets the current frame buffer index.

size_t	PreviousBufferIndex () const noexcept
	Gets the previous frame buffer index.

size_t	FreeSpace () const noexcept
	Gets free space in current buffer.

Static Public Attributes
static constexpr size_t	kBufferCount = 2

Detailed Description

Double-buffered frame allocator.

Maintains two frame buffers, allowing memory from the previous frame to remain valid while allocating for the current frame. Useful when data needs to be accessible for one additional frame (e.g., GPU upload buffers, interpolation).

The allocator automatically switches between buffers on each frame.

Uses atomic for buffer index and frame transitions. Previous frame's data remains valid until the next frame begins. Allocations are lock-free since FrameAllocator uses atomic operations internally.

Note: Thread-safe.

Definition at line 32 of file double_frame_allocator.hpp.

Constructor & Destructor Documentation

◆ DoubleFrameAllocator() [1/3]

helios::memory::DoubleFrameAllocator::DoubleFrameAllocator ( size_t capacity_per_buffer )

inlineexplicit

Constructs a double frame allocator with specified capacity per buffer.

Warning: Triggers assertion if capacity_per_buffer is 0.

Parameters

capacity_per_buffer Size of each buffer in bytes

Definition at line 41 of file double_frame_allocator.hpp.

42 : allocators_{FrameAllocator(capacity_per_buffer), FrameAllocator(capacity_per_buffer)} {}

◆ DoubleFrameAllocator() [2/3]

helios::memory::DoubleFrameAllocator::DoubleFrameAllocator ( const DoubleFrameAllocator & )

delete

◆ DoubleFrameAllocator() [3/3]

helios::memory::DoubleFrameAllocator::DoubleFrameAllocator ( DoubleFrameAllocator && other )

inlinenoexcept

Definition at line 174 of file double_frame_allocator.hpp.

    : allocators_(std::move(other.allocators_)),
      current_buffer_(other.current_buffer_.load(std::memory_order_acquire)) {
  other.current_buffer_.store(0, std::memory_order_release);
}

◆ ~DoubleFrameAllocator()

helios::memory::DoubleFrameAllocator::~DoubleFrameAllocator ( )

defaultnoexcept

Member Function Documentation

◆ Allocate() [1/3]

template<typename T >

T * helios::memory::DoubleFrameAllocator::Allocate ( )

inlinenoexcept

Allocates memory for a single object of type T.

Convenience function that calculates size and alignment from the type. The returned memory is uninitialized - use placement new to construct the object.

Template Parameters

T	Type to allocate memory for

Returns: Pointer to allocated memory, or nullptr on failure

Definition at line 231 of file double_frame_allocator.hpp.

                                                  {
  constexpr size_t size = sizeof(T);
  constexpr size_t alignment = std::max(alignof(T), kMinAlignment);
  auto result = Allocate(size, alignment);
  return static_cast<T*>(result.ptr);
}

◆ Allocate() [2/3]

template<typename T >

T * helios::memory::DoubleFrameAllocator::Allocate ( size_t count )

inlinenoexcept

Allocates memory for an array of objects of type T.

Convenience function that calculates size and alignment from the type. The returned memory is uninitialized - use placement new to construct objects.

Template Parameters

T	Type to allocate memory for

Parameters

count Number of objects to allocate space for

Returns: Pointer to allocated memory, or nullptr on failure

Definition at line 239 of file double_frame_allocator.hpp.

                                                              {
  if (count == 0) [[unlikely]] {
    return nullptr;
  }
  constexpr size_t alignment = std::max(alignof(T), kMinAlignment);
  const size_t size = sizeof(T) * count;
  auto result = Allocate(size, alignment);
  return static_cast<T*>(result.ptr);
}

◆ Allocate() [3/3]

AllocationResult helios::memory::DoubleFrameAllocator::Allocate	(	size_t	size,
		size_t	alignment = `kDefaultAlignment`
	)

inlinenoexcept

Allocates memory from the current frame buffer.

This operation is lock-free as it only reads the atomic buffer index and delegates to the thread-safe FrameAllocator.

Warning

Triggers assertion in next cases:

Alignment is not a power of 2.
Alignment is less than kMinAlignment.

Parameters

size	Number of bytes to allocate
alignment	Alignment requirement (must be power of 2)

Returns: AllocationResult with pointer and actual allocated size, or {nullptr, 0} on failure

Definition at line 193 of file double_frame_allocator.hpp.

                                                                                             {
  // Lock-free: current_buffer_ is atomic, FrameAllocator::Allocate is thread-safe via atomics
  const size_t buffer = current_buffer_.load(std::memory_order_acquire);
  return allocators_[buffer].Allocate(size, alignment);
}

◆ AllocateAndConstruct()

template<typename T , typename... Args>
requires std::constructible_from<T, Args...>

T * helios::memory::DoubleFrameAllocator::AllocateAndConstruct ( Args &&... args )

inlinenoexcept

Allocates and constructs a single object of type T.

Convenience function that allocates memory and constructs the object in-place.

Template Parameters

T	Type to allocate and construct
Args	Constructor argument types

Parameters

args	Arguments to forward to T's constructor

Returns: Pointer to constructed object, or nullptr on allocation failure

Definition at line 251 of file double_frame_allocator.hpp.

                                               {
  T* ptr = Allocate<T>();
  if (ptr != nullptr) [[likely]] {
    std::construct_at(ptr, std::forward<Args>(args)...);
  }
  return ptr;
}

◆ AllocateAndConstructArray()

template<typename T >
requires std::default_initializable<T>

T * helios::memory::DoubleFrameAllocator::AllocateAndConstructArray ( size_t count )

inlinenoexcept

Allocates and default-constructs an array of objects of type T.

Convenience function that allocates memory and default-constructs objects in-place.

Template Parameters

T	Type to allocate and construct (must be default constructible)

Parameters

count Number of objects to allocate and construct

Returns: Pointer to first constructed object, or nullptr on allocation failure

Definition at line 262 of file double_frame_allocator.hpp.

                                              {
  T* ptr = Allocate<T>(count);
  if (ptr != nullptr) [[likely]] {
    for (size_t i = 0; i < count; ++i) {
      std::construct_at(ptr + i);
    }
  }
  return ptr;
}

◆ Capacity()

size_t helios::memory::DoubleFrameAllocator::Capacity ( ) const

inlinenoexcept

Gets the total capacity across both buffers.

Returns: Total capacity in bytes

Definition at line 145 of file double_frame_allocator.hpp.

                                                 {
    return allocators_.front().Capacity() + allocators_.back().Capacity();
  }

◆ CurrentBufferIndex()

size_t helios::memory::DoubleFrameAllocator::CurrentBufferIndex ( ) const

inlinenoexcept

Gets the current frame buffer index.

Returns: Current buffer index (0 or 1)

Definition at line 153 of file double_frame_allocator.hpp.

153{ return current_buffer_.load(std::memory_order_relaxed); }

◆ CurrentFrameStats()

AllocatorStats helios::memory::DoubleFrameAllocator::CurrentFrameStats ( ) const

inlinenoexcept

Gets statistics for the current frame buffer.

Returns: AllocatorStats for current buffer

Definition at line 273 of file double_frame_allocator.hpp.

                                                                             {
  const size_t buffer = current_buffer_.load(std::memory_order_relaxed);
  return allocators_[buffer].Stats();
}

◆ FreeSpace()

size_t helios::memory::DoubleFrameAllocator::FreeSpace ( ) const

inlinenoexcept

Gets free space in current buffer.

Returns: Free space in bytes

Definition at line 283 of file double_frame_allocator.hpp.

                                                             {
  const size_t buffer = current_buffer_.load(std::memory_order_relaxed);
  return allocators_[buffer].FreeSpace();
}

◆ NextFrame()

void helios::memory::DoubleFrameAllocator::NextFrame ( )

inlinenoexcept

Advances to the next frame, switching buffers.

Resets the new current buffer and makes the old current buffer the previous buffer.

Warning: Not thread-safe with Allocate(). Must be called from a single thread while no other threads are allocating. Typically called once per frame by the main thread.

Definition at line 199 of file double_frame_allocator.hpp.

                                                     {
  // Switch to the other buffer
  const size_t new_buffer = 1 - current_buffer_.load(std::memory_order_relaxed);
 
  // Reset the new current buffer before switching
  allocators_[new_buffer].Reset();
 
  // Switch to new buffer
  current_buffer_.store(new_buffer, std::memory_order_release);
}

◆ operator=() [1/2]

DoubleFrameAllocator & helios::memory::DoubleFrameAllocator::operator= ( const DoubleFrameAllocator & )

delete

◆ operator=() [2/2]

DoubleFrameAllocator & helios::memory::DoubleFrameAllocator::operator= ( DoubleFrameAllocator && other )

inlinenoexcept

Definition at line 180 of file double_frame_allocator.hpp.

                                                                                                  {
  if (this == &other) [[unlikely]] {
    return *this;
  }
 
  allocators_ = std::move(other.allocators_);
 
  current_buffer_.store(other.current_buffer_.load(std::memory_order_acquire), std::memory_order_release);
  other.current_buffer_.store(0, std::memory_order_release);
 
  return *this;
}

◆ PreviousBufferIndex()

size_t helios::memory::DoubleFrameAllocator::PreviousBufferIndex ( ) const

inlinenoexcept

Gets the previous frame buffer index.

Returns: Previous buffer index (0 or 1)

Definition at line 159 of file double_frame_allocator.hpp.

                                                            {
    return 1 - current_buffer_.load(std::memory_order_relaxed);
  }

◆ PreviousFrameStats()

AllocatorStats helios::memory::DoubleFrameAllocator::PreviousFrameStats ( ) const

inlinenoexcept

Gets statistics for the previous frame buffer.

Returns: AllocatorStats for previous buffer

Definition at line 278 of file double_frame_allocator.hpp.

                                                                              {
  const size_t buffer = current_buffer_.load(std::memory_order_relaxed);
  return allocators_[1 - buffer].Stats();
}

◆ Reset()

void helios::memory::DoubleFrameAllocator::Reset ( )

inlinenoexcept

Resets both buffers.

Clears all allocations from both buffers.

Definition at line 210 of file double_frame_allocator.hpp.

                                                 {
  allocators_.front().Reset();
  allocators_.back().Reset();
}

◆ Stats()

AllocatorStats helios::memory::DoubleFrameAllocator::Stats ( ) const

inlinenoexcept

Gets combined statistics for both buffers.

Returns: AllocatorStats with combined usage information

Definition at line 215 of file double_frame_allocator.hpp.

                                                                 {
  const AllocatorStats stats0 = allocators_.front().Stats();
  const AllocatorStats stats1 = allocators_.back().Stats();
 
  return {
      .total_allocated = stats0.total_allocated + stats1.total_allocated,
      .total_freed = stats0.total_freed + stats1.total_freed,
      .peak_usage = std::max(stats0.peak_usage, stats1.peak_usage),
      .allocation_count = stats0.allocation_count + stats1.allocation_count,
      .total_allocations = stats0.total_allocations + stats1.total_allocations,
      .total_deallocations = stats0.total_deallocations + stats1.total_deallocations,
      .alignment_waste = stats0.alignment_waste + stats1.alignment_waste,
  };
}

Member Data Documentation

◆ kBufferCount

constexpr size_t helios::memory::DoubleFrameAllocator::kBufferCount = 2

staticconstexpr

Definition at line 34 of file double_frame_allocator.hpp.

	Helios Engine 0.1.0 A modular ECS based data-oriented C++23 game engine

Public Member Functions

Static Public Attributes

Detailed Description

Constructor & Destructor Documentation

◆ DoubleFrameAllocator() [1/3]

◆ DoubleFrameAllocator() [2/3]

◆ DoubleFrameAllocator() [3/3]

◆ ~DoubleFrameAllocator()

Member Function Documentation

◆ Allocate() [1/3]

◆ Allocate() [2/3]

◆ Allocate() [3/3]

◆ AllocateAndConstruct()

◆ AllocateAndConstructArray()

◆ Capacity()

◆ CurrentBufferIndex()

◆ CurrentFrameStats()

◆ FreeSpace()

◆ NextFrame()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ PreviousBufferIndex()

◆ PreviousFrameStats()

◆ Reset()

◆ Stats()

Member Data Documentation

◆ kBufferCount