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karnkaulkarnkaul
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WIP: Buffers
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‎guide/src/SUMMARY.md‎

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- [Memory Allocation](memory/README.md)
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- [Vulkan Memory Allocator](memory/vma.md)
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- [Buffers](memory/buffers.md)

‎guide/src/memory/buffers.md‎

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# Buffers
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First add the RAII wrapper components for VMA buffers:
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```cpp
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struct RawBuffer {
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VmaAllocator allocator{};
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VmaAllocation allocation{};
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vk::Buffer buffer{};
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vk::DeviceSize capacity{};
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vk::DeviceSize size{};
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void* mapped{};
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auto operator==(RawBuffer const& rhs) const -> bool = default;
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};
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struct BufferDeleter {
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void operator()(RawBuffer const& raw_buffer) const noexcept;
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};
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// ...
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void BufferDeleter::operator()(RawBuffer const& raw_buffer) const noexcept {
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vmaDestroyBuffer(raw_buffer.allocator, raw_buffer.buffer,
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raw_buffer.allocation);
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}
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```
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Buffers can be backed by host (RAM) or device (VRAM) memory: the former is mappable and thus useful for data that changes every frame, latter is faster to access for the GPU but needs more complex methods to copy data from the CPU to it. Add the relevant subset of parameters and the RAII wrapper:
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```cpp
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enum class BufferType : std::int8_t { Host, Device };
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struct BufferCreateInfo {
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vk::BufferUsageFlags usage{};
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vk::DeviceSize size{};
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BufferType type{BufferType::Host};
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};
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class Buffer {
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public:
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using CreateInfo = BufferCreateInfo;
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explicit Buffer(VmaAllocator allocator, CreateInfo const& create_info);
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[[nodiscard]] auto get_type() const -> Type {
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return m_buffer.get().mapped == nullptr ? Type::Device : Type::Host;
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}
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[[nodiscard]] auto get_usage() const -> vk::BufferUsageFlags {
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return m_usage;
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}
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[[nodiscard]] auto get_raw() const -> RawBuffer const& {
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return m_buffer.get();
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}
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auto resize(vk::DeviceSize size) -> bool;
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private:
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auto create(VmaAllocator allocator, vk::DeviceSize size) -> bool;
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Scoped<RawBuffer, BufferDeleter> m_buffer{};
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vk::BufferUsageFlags m_usage{};
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};
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```
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`resize()` and `create()` are separate because the former uses the existing `m_buffer`'s allocator. The implementation:
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```cpp
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[[nodiscard]] constexpr auto positive_size(vk::DeviceSize const in) {
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return in > 0 ? in : 1;
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}
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// ...
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Buffer::Buffer(VmaAllocator allocator, CreateInfo const& create_info)
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: m_usage(create_info.usage) {
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create(allocator, create_info.type, create_info.size);
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}
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auto Buffer::resize(vk::DeviceSize const size) -> bool {
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if (size <= m_buffer.get().capacity) {
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m_buffer.get().size = size;
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return true;
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}
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return create(m_buffer.get().allocator, get_type(), size);
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}
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auto Buffer::create(VmaAllocator allocator, Type const type,
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vk::DeviceSize size) -> bool {
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// buffers cannot be zero sized.
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size = positive_size(size);
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auto allocation_ci = VmaAllocationCreateInfo{};
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allocation_ci.flags =
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VMA_ALLOCATION_CREATE_HOST_ACCESS_SEQUENTIAL_WRITE_BIT;
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if (type == BufferType::Device) {
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allocation_ci.usage = VMA_MEMORY_USAGE_AUTO_PREFER_DEVICE;
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} else {
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allocation_ci.usage = VMA_MEMORY_USAGE_AUTO_PREFER_HOST;
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allocation_ci.flags |= VMA_ALLOCATION_CREATE_MAPPED_BIT;
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}
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auto buffer_ci = vk::BufferCreateInfo{};
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buffer_ci.setSize(size).setUsage(m_usage);
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auto vma_buffer_ci = static_cast<VkBufferCreateInfo>(buffer_ci);
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VmaAllocation allocation{};
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VkBuffer buffer{};
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auto allocation_info = VmaAllocationInfo{};
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auto const result =
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vmaCreateBuffer(allocator, &vma_buffer_ci, &allocation_ci, &buffer,
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&allocation, &allocation_info);
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if (result != VK_SUCCESS) {
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std::println(stderr, "Failed to create VMA Buffer");
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return false;
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}
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m_buffer = RawBuffer{
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.allocator = allocator,
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.allocation = allocation,
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.buffer = buffer,
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.capacity = size,
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.size = size,
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.mapped = allocation_info.pMappedData,
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};
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return true;
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}
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```

‎guide/src/memory/vma.md‎

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} // namespace lvk::vma
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// vma.cpp
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void vma::Deleter::operator()(VmaAllocator allocator) const noexcept {
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void Deleter::operator()(VmaAllocator allocator) const noexcept {
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vmaDestroyAllocator(allocator);
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}
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// ...
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auto vma::create_allocator(vk::Instance const instance,
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vk::PhysicalDevice const physical_device,
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vk::Device const device) -> Allocator {

‎src/app.cpp‎

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create_surface();
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select_gpu();
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create_device();
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create_allocator();
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create_swapchain();
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create_render_sync();
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create_imgui();

‎src/scoped.hpp‎

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namespace lvk {
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template <typename Type>
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concept Scopeable =
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std::equality_comparable<Type> && std::is_default_constructible_v<Type>;
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concept Scopeable = std::equality_comparable<Type>;
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template <Scopeable Type, typename Deleter>
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class Scoped {

‎src/vma.cpp‎

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#include <vma.hpp>
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#include <print>
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#include <stdexcept>
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namespace lvk {
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void vma::Deleter::operator()(VmaAllocator allocator) const noexcept {
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namespace vma {
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namespace {
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[[nodiscard]] constexpr auto positive_size(vk::DeviceSize const in) {
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return in > 0 ? in : 1;
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}
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} // namespace
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void Deleter::operator()(VmaAllocator allocator) const noexcept {
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vmaDestroyAllocator(allocator);
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}
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void BufferDeleter::operator()(RawBuffer const& raw_buffer) const noexcept {
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vmaDestroyBuffer(raw_buffer.allocator, raw_buffer.buffer,
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raw_buffer.allocation);
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}
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Buffer::Buffer(VmaAllocator allocator, CreateInfo const& create_info)
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: m_usage(create_info.usage) {
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if (create_info.type == Type::Device) {
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// device buffers require a transfer operation to copy data.
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m_usage |= vk::BufferUsageFlagBits::eTransferDst;
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}
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create(allocator, create_info.type, create_info.size);
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}
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auto Buffer::resize(vk::DeviceSize const size) -> bool {
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if (size <= m_buffer.get().capacity) {
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m_buffer.get().size = size;
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return true;
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}
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return create(m_buffer.get().allocator, get_type(), size);
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}
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auto Buffer::create(VmaAllocator allocator, Type const type,
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vk::DeviceSize size) -> bool {
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// buffers cannot be zero sized.
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size = positive_size(size);
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auto allocation_ci = VmaAllocationCreateInfo{};
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allocation_ci.flags =
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VMA_ALLOCATION_CREATE_HOST_ACCESS_SEQUENTIAL_WRITE_BIT;
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if (type == BufferType::Device) {
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allocation_ci.usage = VMA_MEMORY_USAGE_AUTO_PREFER_DEVICE;
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} else {
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allocation_ci.usage = VMA_MEMORY_USAGE_AUTO_PREFER_HOST;
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allocation_ci.flags |= VMA_ALLOCATION_CREATE_MAPPED_BIT;
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}
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auto buffer_ci = vk::BufferCreateInfo{};
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buffer_ci.setSize(size).setUsage(m_usage);
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auto vma_buffer_ci = static_cast<VkBufferCreateInfo>(buffer_ci);
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VmaAllocation allocation{};
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VkBuffer buffer{};
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auto allocation_info = VmaAllocationInfo{};
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auto const result =
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vmaCreateBuffer(allocator, &vma_buffer_ci, &allocation_ci, &buffer,
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&allocation, &allocation_info);
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if (result != VK_SUCCESS) {
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std::println(stderr, "Failed to create VMA Buffer");
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return false;
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}
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m_buffer = RawBuffer{
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.allocator = allocator,
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.allocation = allocation,
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.buffer = buffer,
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.capacity = size,
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.size = size,
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.mapped = allocation_info.pMappedData,
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};
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return true;
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}
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} // namespace vma
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auto vma::create_allocator(vk::Instance const instance,
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vk::PhysicalDevice const physical_device,
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vk::Device const device) -> Allocator {

‎src/vma.hpp‎

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#include <vk_mem_alloc.h>
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#include <scoped.hpp>
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#include <vulkan/vulkan.hpp>
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#include <cstdint>
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namespace lvk::vma {
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struct Deleter {
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[[nodiscard]] auto create_allocator(vk::Instance instance,
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vk::PhysicalDevice physical_device,
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vk::Device device) -> Allocator;
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struct RawBuffer {
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VmaAllocator allocator{};
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VmaAllocation allocation{};
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vk::Buffer buffer{};
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vk::DeviceSize capacity{};
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vk::DeviceSize size{};
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void* mapped{};
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auto operator==(RawBuffer const& rhs) const -> bool = default;
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};
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struct BufferDeleter {
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void operator()(RawBuffer const& raw_buffer) const noexcept;
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};
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enum class BufferType : std::int8_t { Host, Device };
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struct BufferCreateInfo {
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vk::BufferUsageFlags usage{};
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vk::DeviceSize size{};
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BufferType type{BufferType::Host};
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};
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class Buffer {
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public:
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using CreateInfo = BufferCreateInfo;
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using Type = BufferType;
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explicit Buffer(VmaAllocator allocator, CreateInfo const& create_info);
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[[nodiscard]] auto get_type() const -> Type {
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return m_buffer.get().mapped == nullptr ? Type::Device : Type::Host;
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}
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[[nodiscard]] auto get_usage() const -> vk::BufferUsageFlags {
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return m_usage;
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}
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[[nodiscard]] auto get_raw() const -> RawBuffer const& {
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return m_buffer.get();
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}
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auto resize(vk::DeviceSize size) -> bool;
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private:
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auto create(VmaAllocator allocator, Type type, vk::DeviceSize size) -> bool;
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Scoped<RawBuffer, BufferDeleter> m_buffer{};
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vk::BufferUsageFlags m_usage{};
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};
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} // namespace lvk::vma

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