Panda3DS/include/renderer_mtl/mtl_vertex_buffer_cache.hpp

#pragma once

#include <cstring>

#include "helpers.hpp"
#include "pica_to_mtl.hpp"


using namespace PICA;

namespace Metal {
	struct BufferHandle {
		MTL::Buffer* buffer;
		usize offset;
	};

	class VertexBufferCache {
		// 128MB buffer for caching vertex data
		static constexpr usize CACHE_BUFFER_SIZE = 128 * 1024 * 1024;

	  public:
		VertexBufferCache() = default;

		~VertexBufferCache() {
			endFrame();
			buffer->release();
		}

		void set(MTL::Device* dev) {
			device = dev;
			create();
		}

		void endFrame() {
			ptr = 0;
			for (auto buffer : additionalAllocations) {
				buffer->release();
			}
			additionalAllocations.clear();
		}

		BufferHandle get(const void* data, usize size) {
			// If the vertex buffer is too large, just create a new one
			if (ptr + size > CACHE_BUFFER_SIZE) {
				MTL::Buffer* newBuffer = device->newBuffer(data, size, MTL::ResourceStorageModeShared);
				newBuffer->setLabel(toNSString("Additional vertex buffer"));
				additionalAllocations.push_back(newBuffer);
				Helpers::warn("Vertex buffer doesn't have enough space, creating a new buffer");

				return BufferHandle{newBuffer, 0};
			}

			// Copy the data into the buffer
			std::memcpy((char*)buffer->contents() + ptr, data, size);

			auto oldPtr = ptr;
			ptr += size;

			return BufferHandle{buffer, oldPtr};
		}

		void reset() {
			endFrame();

			if (buffer) {
				buffer->release();
				create();
			}
		}

	  private:
		MTL::Buffer* buffer = nullptr;
		usize ptr = 0;
		std::vector<MTL::Buffer*> additionalAllocations;

		MTL::Device* device;

		void create() {
			buffer = device->newBuffer(CACHE_BUFFER_SIZE, MTL::ResourceStorageModeShared);
			buffer->setLabel(toNSString("Shared vertex buffer"));
		}
	};
}  // namespace Metal